statistical analysis and optimization of ammonia removal from landfill leachate by sequential...

7232019 Statistical Analysis and Optimization of Ammonia Removal From Landfill Leachate by Sequential Microwave_aeratihellip

httpslidepdfcomreaderfullstatistical-analysis-and-optimization-of-ammonia-removal-from-landfill-leachate 19

Statistical

analysis and

optimization of

ammonia

removal from

land1047297llleachate

by

sequential

microwaveaeration

process using

factorialdesign

and

response

surface

methodology

Sainan Dong Majid Sartaj

University of Ottawa Department of Civil Engineering 161 Louis Pasteur Ottawa Ontario K1N 6N5 Canada

A

R

T

I

C

L

E

I

N

F

O

Article historyReceived 10 June 2015Received in revised form 20 October 2015Accepted 22 October 2015Available online 30 October 2015

Keywords

AmmoniaMicrowaveAerationLeachateFactorial designResponse surface methodology

A

B

S

T

R

A

C

T

The application of microwave (MW) radiation followed by aeration (A) for the purpose of ammoniaremoval from both synthetic solutions and land1047297ll leachate was investigated in this study 100mL of synthetic solution or land1047297ll leachatewas subjected toMWradiation for 30 45 60 90 and 120s under50and 100poweroutputleveland a pHof10105and 11 Thesampleswere then aeratedfor10min Theinitial after MWapplication and 1047297nal total ammonia nitrogen (TAN)were measured Results con1047297rmedthat the sequentialmicrowaveaeration process wasan effectiveapproach for removal of ammonia fromaqueous systemsMaximum ammonia removal of 817for 100mLsynthetic solutionand70 for100mL land1047297ll leachatewasachieved byapplying 78KJ microwaveenergyoutput and 10minaeration Factorialdesign and response surface methodology were applied to evaluate and optimize the effects of pH MWenergyleveland microwave poweroutputWhen applying thesame energyoutputto thebatch tests theeffect of varyingMWpower output is negligible For 100mL synthetic ammonia solution the optimumpH and MWenergy output level for ammonia removal were 11 and 78KJ and the maximum ammoniaremoval ef 1047297ciency predicted for the synthetic solution is 763 R2 of 0941 indicates that the observedresults 1047297tted well with the model prediction

atilde

2015 Elsevier Ltd All rights reserved

1 Introduction

As

one

of

the

major

inorganic

pollutants

in

surface

waterammonia

exists

in

aqueous

solution

in

two

forms

un-ionizedammonia (NH3) and ionized ammonia (NH4

+) [1] It is common inaquatic chemistry to refer to and express the sum of NH3 and NH4

+

as

simply

ammonia

or

total

ammonia

nitrogen

(TAN)

[2]

Previousresearch

has

shown

that

toxicity

is

mainly

due

to

NH3 form

[34]The concentration distribution of the ionized and un-ionizedammonia depends on pH temperature and total ammoniaconcentration

Under

low

pH

conditions

the

majority

of

TAN

is

in the form of NH4+ while under high pH conditions NH3 becomesthe dominant species [1] Agricultural drainage and wastewatersfrom steel fertilizer petroleum and meat-processing industriesand

land1047297ll leachate

are

the

main

sources

of

ammonia

in

naturalwater

bodies

[5]

According

to

the

EPArsquos

fresh

water

criteriaammonia is toxic to aquatic organisms even at low levels (19 mgL as TAN at 20 C and pH of 7) [6] Also discharge of wastewater with

high ammonia concentration can increase nitrogen levels innatural aqueous systems thus causing eutrophication [7]

With

the

increase

of

population

and

life

quality

globally

thegeneration

of

municipal

solid

waste

(MSW)

has

increased

rapidlyover the past 30 years EPA data shows that the total MSWgeneration in the US in 1980 was 1516 million tons this increasedto

2537

tons

by

the

year

2005

and

remained

approximately

at

thesame

level

until

2012

[8]

The

most

common

MSW

managementapproach is land1047297lling due to easy operation procedures and lowcost One of the main concerns associated with land1047297lling processis

leachate

generation

which

is

one

kind

of

hazardous

and

severely

polluted wastewater that contains large amounts of organicmatters ammonia nitrogen heavy metals chlorinated organicand inorganic salts [9] Mature land1047297ll leachate is usuallycharacterized

by

a

low

BODCOD

ratio

as

low

as

004

and

highNH3-N

level

up

to

13000

mgL

[10]

Ward

et

al

reported

that

thesigni1047297cant toxicity of leachate from a land1047297ll in Florida was due tothe presence of ammonia [11]

Traditional

biological

processes

for

treatment

of

ammoniaincorporate

nitri1047297cation

and

denitri1047297cation

and

they

do

notperform well to high concentration of ammonia in land1047297ll leachatewhich could inhibit microbial activities including the nitri1047297cation

Corresponding

authorE-mail addresses msartajuottawaca msartajyahoocom (M Sartaj)

httpdxdoiorg101016jjece2015100292213-3437atilde 2015 Elsevier Ltd All rights reserved

Journal

of

Environmental

Chemical

Engineering

4

(2016)

100ndash108

Contents

lists

available

at

ScienceDirect

Journal

of

Environmental

Chemical

Engineering

journal homepage wwwelseviercomlocate je ce



process The inhibition of the nitri1047297cation process is reported to bedue

to

NH3 form

while

the

presence

of

NH4-N

in

the

aqueoussolution

is

reported

to

inhibit

the

NO2-N

oxidation

process

atconcentrations of 20 mgL and also begins to inhibit the NH4-Noxidation process at concentrations of 100 mgL of [NH4-N] [5]Ammonia

inhibition

effects

on

microorganisms

in

biologicaltreatments

have

also

been

reported

in

the

range

of

1500ndash5000 mgL as TAN by other researchers [1213]

For wastewaters with high ammonia concentration physicaland

chemical

methods

have

been

reported

to

exhibit

high

removalef 1047297ciencies

However

physical

and

chemical

methods

usuallycome with high cost and some other issues such as the largevolume of contaminated sludge generated from the 1047298occulationand

coagulation

approach

as

well

as

the

long

contact

time

duringthe

stripping

process

[1415]Considering cost and removal ef 1047297ciency the application of

chemicalphysical methods as a pretreatment for the highammonia

concentration

before

biological

processes

could

be

aneffective

option

The

biological

processes

require

a

proper

CN

ratioaround 201 for the aerobic treatment and 401 for the anaerobicprocess Since high ammonia levels in the leachate usually result ina

low

CN

ratio

in

the

system

the

pretreatment

could

reduce

theammonia

concentration

while

still

retaining

enough

carbon

sources for the biological process [16]Microwave (MW) radiation has been widely applied in the

environmental

1047297eld

for

the

sludge

and

wastewater

treatments

[17ndash20]

MW

enhanced

oxidation

processes

with

oxidants

such

ashydrogen peroxide (H2O2) and persulfate (S2O8

2) increased thedegradation rate of COD and some micro-pollutants such as acidorange

7

(AO7)

bromophenol

blue

phenol

and

pharmaceuticalwastewater

[21]MW radiation under high pH levels was reported to reduce

ammonia signi1047297cantly without affecting the organic compounds[22]

It

was

observed

that

when

applying

350

W

microwaveradiation the MW radiation process (below the boiling point) wasresponsible for 40 of the ammonia removal The remainingportion

of

the

dissipated

ammonia

was

removed

in

the

following

two minutes after the solution reached the boiling point by acombination of MW and thermal processes Meanwhile whenaeration process was applied concurrently with MW radiationprocess

the

contribution

of

aeration

decreased

with

longerradiation

time

However

the

continuous

boiling

process

employedin the research by Lin et al [22] could be a safety concern due to thehigh operation temperatures and may possibly generate unknownsecondary

pollutants

when

applied

to

real

land1047297ll

leachateMoreover

when

MW

radiation

has

been

used

as

a

pretreatmentapproach the high ef 1047298uent temperature can have a negative effecton the subsequent biological treatment processes

Aeration

is

another

effective

physical

treatment

for

the

removalof

ammonia

without

affecting

carbon

sources

in

the

aqueoussystem The main drawback of the aeration process is the energy

expenditure

the

need

to

raise

pH

and

the

contact

time

required[23]

Mattinen

et

al

reported

89

ammonia

reduction

at

pH

11with

24

h

contact

time

[24]

In

a

similar

research

the

maximumammonia removal ef 1047297ciency was found at 85 for a land1047297llleachate with approximately 1000 mgL ammonium nitrogen atpH

of

12

with

17

h

contact

time

[14]In

this

study

a

sequential

MW

radiation

followed

by

aerationprocess was systematically applied for ammonia removal fromaqueous phase (synthetic solution) under different MW poweroutput

pH

and

radiation

time

based

on

a

factorial

experimentaldesign

Response

surface

methodology

(RSM)

was

also

applied

toevaluate and optimize the effect of pH MW power output andradiation time For both safety and economic concerns the sampleswere

maintained

below

the

boiling

point

The

temperature

of

the

samples

was

signi1047297

cantly

increased

during

the

MW

radiation

stage and then decreased through subsequent aeration processAnd

lastly

the

MW

treatments

with

and

without

aerationprocesses

were

applied

for

the

ammonia

removal

from

a

realland1047297ll leachate

2

Material

and

methods

21 Materials and equipment

The

synthetic

solution

which

contained

2700

mgL

total

TANwas

prepared

by

dissolving

analytical

grade

ammonia

chloride(Fisher Scienti1047297c) in distilled water As mentioned above ammoniainhibitory effects in biological treatments in the range of 1500ndash5000

mgL

as

TAN

have

been

reported

[1213] As

such

it

wasdecided

to

select

an

initial

concentration

of

2700

mgL

total

TANwhich is within the inhibitory range In each test 100 mL of thefresh synthetic solution were prepared The initial pH was around57

The

pH

was

adjusted

to

the

desired

value

using

10

molL

NaOHThe

land1047297ll

leachate

was

obtained

from

a

local

land1047297ll

in

Ottawawith the initial pH 90 02 and TAN concentration of about4000 mgL

The

MW

process

was

carried

out

by

a

Panasonic

microwaveoven

(Model

NN-S

750)

with

an

operating

frequency

of

2450

MHz

and power consumption of 1320 W The maximum power outputwas 1300 W and could be adjusted from 10 to 100 in 10intervals

The

aeration

process

was

performed

using

a

Model

200

MARINApump with a total aeration rate of 110 Lh with 2 air diffusers Ineach test only one diffuser was placed in the batch reactor For thetests

carried

out

with

the

synthetic

solution

a

150

mL

beaker

wasused

as

the

batch

reactor

for

all

MW

with

and

without

aerationprocesses For the land1047297ll leachate a 1 L beaker was used as thebatch reactor for the microwave process and a 4 L glass containerwas

used

for

the

aeration

process

22 Analytical methods

TNT 832 ammonia vials from HACH Company were used to testammonia concentrations based on the Salicylate Method using aHACH DR5000 Spectrophotometer The 10 mgL ammonia nitrogenstandard

solution

from

HACH

Company

was

used

to

check

thespectrophotometer

The

pH

was

measured

using

a

glass

electrodein combination with a Fisher Accumet1Model XL25 dual channelpHion meter

23

Experimental

design

For this study MW and aeration were performed in sequenceExperimental

conditions

for

the

tests

conducted

are

summarizedin

Table

1 The

pH

range

was

selected

based

on

the

results

of

apreliminary set of experiments which was conducted to evaluate

the

effect

of

pH

on

process

ef 1047297ciency

At

a

100

power

MWradiation

times

greater

than

90

s

resulted

in

boiling

of

the

samples

Table 1

Experimental design of MW processes for the synthetic solution

MW time (s) 30 45 60 90 120

Power output level () 50 100 50 100 50 100 50 100 50 100

pH 10 U U ndash U U U U ndash U ndash

105 U U

ndash U U U U

ndash U

ndash

11 U U ndash U U U U ndash U ndash

U Experiments conducted under these conditionsndash No experiments conducted under these conditions

S Dong M Sartaj Journal of Environmental Chemical Engineering 4 (2016) 100ndash108 101



and hence they were not carried out For MW + A the aeration timewas

kept

at

10

min

for

all

samples

The

aeration

time

was

selectedbased

on

another

preliminary

set

of

testsMW with and without aeration process for land1047297ll leachate was

conducted using 50 power output with 120 s radiation time underthree

pH

levels

of

10

105

11

and

10

min

of

aeration

if

applicableFig

1

presents

the

order

of

tests

carried

out

For

the

each

test100 mL of either synthetic solution or leachate was used pH wasadjusted to desired level using 10 molL NaOH solution The samplewas

then

exposed

to

MW

radiation

for

the

desired

radiation

timeaccording

to

the

conditions

presented

in

Table

1 The

sampletemperature was measured immediately after the MW treatmentDistilled water was used to compensate any water loss Then TANpH

and

temperature

of

the

sample

were

measured

The

sample

wasaerated

10

min

and

TAN

pH

and

temperature

was

measured

againafter another adjustment for water loss

24 Statistical method and data analysis

Factorial design and response surface methodology (RSM) wereapplied

to

evaluate

and

optimize

the

pH

and

MW

energy

output

forammonia

removal

from

aqueous

systems

MW

energy

output

was

used to investigate the combined effect of MW power output andradiation time Two independent variables X 1 (MW energy output)and

X 2 (pH)

were

used

for

the

response

surface

model

and

theoutcome

response

was Y (ammonia

removal

rate)

As

shown

inTable 2 X 1 was coded at four levels from 1 to 1 X 2 was coded atthree

levels

between 1

and

1 The

ranges

of

the

individual

factorswere

chosen

from

the

preliminary

test

All

tests

were

carried

out

intriplicates with the purpose of obtaining a reliable estimate of therandom error and to reduce the noise and bias for the outcomeresponse

Statistical

analysis

was

performed

using

DesignExpert1 soft-ware Ammonia removal ef 1047297ciency (Y ) was calculated using thefollowing equation [1]

Y

eth THORN

frac14

C C 0C 0

100

eth1THORN

where

C

is

the

ammonia

nitrogen

concentration

after

treatmentand

C 0 is

the

initial

ammonia

nitrogen

concentrationAs a combination of mathematical and statistical techniques

response surface methodology (RSM) has been widely used toacquire

the

optimal

operation

conditions

for

both

laboratory

andindustrial

processes

[27]

In

this

study

the

optimum

operationconditions for ammonia removal were obtained by analyzing therelationships between the variables (pH and MW energy output)and

the

response

(ammonia

removal)

The

behaviour

of

the

RSM

inthis

study

was

expressed

by

the

following

second-order

polynomial

equation

[12526]

Y frac14 A0 thornXn

ifrac141 Ai X i thorn

Xn

ifrac141 Aii X 2i thorn

Xn

i6frac141 jfrac141 Aij X i X j thorn

e eth2THORN

where

Y

is

the

response

variable

A0 is

the

value

of

the

1047297xedresponse

at

the

center

point

of

the

design

Ai

Aii

Aij

represents

thelinear quadratic and second order effect regression terms n is thenumber of independent variable and

e is the random errorCoef 1047297cient

of

determination

(R2)

was

used

to

describe

the

accuracyof

the

model

F

value

(Fisher

variation

ratio)

and

probability

value(Prob gt F ) were applied to evaluate the signi1047297cance of the modelterms [128]

3

Results

and

discussion

31 Effect of power output

Based

on

a

preliminary

set

of

tests

a

pH

of

105

was

identi1047297ed

asthe optimum pH for the ammonia removal by MW from syntheticsolution As mentioned above three pH levels of 10 105 and11

were

investigated

in

this

study

Two

power

output

levels

used

inthis

test

were

100

(1300

W)

and

50

(750

W)

of

the

total

MWpower output As shown in Eq (3) the energy output wascalculated according to the corresponding MW irradiation time

E frac14 P t

1000 eth3THORN

where

E

is

the

MW

energy

output

KJ

P

is

the

power

output

W

t

isthe

MW

irradiation

time

In

order

to

test

the

ammonia

removal

at

two

power

outputlevels while maintaining the same energy output for the twopower

levels

the

radiation

time

used

for

100

power

output

levelwas

half

the

radiation

time

for

50

of

the

power

output

levelAs shown in Fig 2 ammonia removal ef 1047297ciency increased with

increasing MW energy output under all three pH levels Similarresults

were

obtained

by

Rabah

and

Darwish

[29]

and

Lin

et

al[22]

Also

under

the

lower

energy

output

values

the

difference

forammonia removal ef 1047297ciencies obtained from 50 and 100 MWpower output were not considerable However the difference inammonia

removal

ef 1047297ciencies

for

50

and

100

MW

power

outputincreases

for

higher

energy

output

levels

and

it

is

dependent

on

Fig

1

Experimental 1047298

ow

chart

Table 2

Experimental design and the levels of independent process variables

Independent variable Symbol Coded levels

1 033 0 033 1

MW energy output (KJ) X 1 195 39 ndash 585 78pH X 2 10 ndash 105 ndash 11

102 S Dong M Sartaj Journal of Environmental Chemical Engineering 4 (2016) 100ndash108



pH

At

a

pH

of

10

higher

ammonia

removal

of

675

was

obtainedusing

100

of

the

total

MW

power

output

than

the

value

of

64using

50

MW

power

output

At

pH

levels

of

105

and

11

the

50power

output

groups

had

slightly

higher

removal

ef 1047297ciencies

thanthe

100

groups

However

for

the

MW

+

A

method

the

differences

of ammonia removal ef 1047297ciencies obtained from 50 and 100 MWpower

output

tests

were

negligible

Thus

in

the

modeling

processthe

ammonia

removal

data

were

catalogued

by

the

MW

energyoutput level instead MW radiation time and power output level

Depending

on

the

energy

output

and

pH

levels

the

MW

processcan

remove

between

109

and

531

TAN

in

the

synthetic

solutionWhen

applying

the

sequential

aeration

process

an

additional205ndash452 TAN removal can be achieved depending on theoperation

parameters

32 Statistical analysis and modeling

After

performing

63

runs

based

on

a

factorial

design

of

twoindependent

variables

the

experimental

results

for

ammonia

percent removal (Y ) were obtained All the data was evaluated byDesignExpert1 to

detect

any

outlier

and

unreliable

result

Externalstudentized

residuals

were

calculated

to

eliminate

the

outliers

Allcollected data was in the acceptable range to be used to develop themodel Regression analysis was applied to develop the best-1047297tmodel

using

the

collected

data

The

response

ammonia

removalpercentage

(Y )

was

predicted

by

a

second-order

polynomialequation shown as Eq (4) below

Y frac14 5449 thorn 2111 X 1 thorn 320 X 2 thorn 165 X 1 X 2 112 X 21 207 X 22 eth4THORN

where Y is the ammonia removal ef 1047297ciency X 1 is the MW energyoutput

X 2 is

the

adjusted

pH

value

of

the

sampleF -test

was

conducted

for

the

analysis

of

variance

(ANOVA)

toevaluate

the

statistical

signi1047297cance

of

the

quadratic

model

TheANOVA tests results are as shown in Table 3(a) The F -value of 19722 and the ldquoProb gt F rdquo value of lt00001 suggests that the modelwas

statistically

signi1047297cant

for

ammonia

removal

Values

of ldquoProb

gt F rdquo

less

than

005

indicate

model

terms

are

signi1047297cant

In

this

case

X 1

X 2

and

X 22 are

signi1047297cant

model

terms

For

terms

X 1 X 2

and X 21 the

corresponding

ldquoProb

gt F rdquo

values

are

larger

than

005which

implies

these

are

insigni1047297cant

terms

and

can

be

eliminatedThe ANVOA test results of the reduced form are as shown in

Table

3(b)

As

can

be

seen

the

reduced

model

with

F

value

of 31157 and

ldquoProb

gt

F rdquo

value

of

lt00001

indicate

that

the

reducedmodel

is

signi1047297cant

There

is

only

a

001

chance

that

the

large

F -value is a result of noise The adequate precision ratio of 5082 indicates an adequate signal since it is larger than theBoundary

value

of

4

[3031]

The

reduced

model

of

ammoniaremoval

percentage

is

shown

as

Eq

(5)

below

Y frac14 5397 thorn 2094 X 1 thorn 344 X 2 207 X 22 eth5THORN

Coef 1047297cient

of

determination

(R2)

adjusted

R2 and

predicted

R2

values were used to evaluate the 1047297tness of the model Adjusted R2

is a modi1047297cation of R2 which adjusts for the number of explanatoryterms

in

a

model

relative

to

the

number

of

data

points

[32] Thepredicted

R2 indicates

how

well

a

regression

model

predicts

responses

for

new

observations

[33]

The

R2

value

of

0941(R2adj frac14

0937)

indicates

that

the

predicted

values

obtained

from

the

model

is

a

good

1047297t of

the

experimental

data

[29]

The

lack-of-1047297tcompares

the

residual

error

to

the

pure

error

from

triplicatedexperimental design points [126] In the full model the p-value forlack-of-1047297t is 0052 which is greater than 005 indicating that thelack-of-1047297t

is

insigni1047297cant

relative

to

the

pure

error

There

is

a

54chance

that

the

lack-of-1047297t

occurs

due

to

noise

or

random

errorwhich means there was no lack-of-1047297t of the model However in thereduced model the lack-of-1047297t value is 0028 which implies thelack-of-1047297t

is

signi1047297cant

in

the

reduced

model

This

could

due

to

thesystematic

variations

unaccounted

for

in

the

model

[34] Anotherpossible reason is that the large numbers (up to 6) of close replicatevalues that used to provide an estimate of pure error [130] A

relatively

low R

2

value

and

the

signi1047297cant

lack-of-1047297t value

cansuggest

that

regression

model

fails

to

adequately

describe

thefunctional relationship between the experimental factors and theresponse variable adequately [35] However a model withreasonable

R2 value

is

acceptable

with

signi1047297cant

lack-of-1047297t[36ndash38]

Compared

with

the

reduced

model

the

differencebetween R2 values is not considerable and the reduced model issimpler ie has less terms The reduced quadratic model wasconsidered

to

be

appropriate

to

describe

the

design

due

with

a

highR2 value

of

0941

and

adequate

precision

ratio

of

5082Fig 3 illustrates the predicted versus observed values for

ammonia

removal

Actual

values

are

collected

from

each

speci1047297crun

and

predicted

values

are

produced

by

the

model

of

Eq

(2)

Thelinear distribution of the points along the idealized trend indicates

Fig 2 Ammonia removal using the same energy output with 50 and 100 of thetotal power output under pH of 10 (a) 105 (b) 11(c)




Actual

P r e d i c t e d

Predicted vs Actual

20

30

40

50

60

70

80

90

20

30

40

50

60

70

80

90

Fig 3

Predicted

versus

actual

values

for

ammonia

percent

removal

Table 3

Analysis of variance (ANOVA) for RSM (a) full and (b) reduced quadratic model parameters

(a)

Source Sum of squares df Mean square F value p-value Prob gt F

Model 1361464 5 272293 19722 lt00001 Signi1047297cant X 1 1244230 1 1244230 90118 lt00001 X 2 41249 1 41249 2988

lt00001 X 1X2 5364 1 5364 388 0054

X 21 1445 1 1445 105 0311

X 22 5990 1 5990 434 0042

Residual 78698 57 1381Lack-of-1047297t 16556 6 2760 226 0052 Not signi1047297cantPure error 62142 51 1218Total 1440162 62R2= 0945 R2adj frac14 0941 R2pred frac14 0933 Adequate precision = 42402

(b)


Model 1354655 3 4515512 31157

lt00001 Signi1047297cant X 1 1299065 1 1299065 89636

lt00001 X 2 496009

1

49601

3423

lt00001

X 22 5990 1 5990 413 0047

Residual 85506 59 1449Lack-of-1047297t 23364 8 2921 240 0028 Signi1047297cant

Pure

error

62142

51

1218Total 1440162 62R2= 0941 R2adj frac14 0937 R2pred frac14 0932 Adequate precision = 5082




the

predicted

values

are

good

approximations

of

the

correspondingobserved

values

The R2 value

of

0964

indicates

a

high

correlationbetween the actual and predicted values for this model

Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was

producedby the software based on the externally studentized to de1047297neoutliers

No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there

is no signi1047297cantdistribution

pattern

for all the

diagnostics

plots

graphs

and

all the

Fig 4 Diagnostics plots for ammonia removal (a) externally studentized residual versus predicted values (b) externally studentized residual versus run values




Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal

Fig 6 Three-dimensional surface plot by response surface methodology




externally

studentized residual were

randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals

versusnormal probability

percentage

con1047297rming

that

the

statisticalassumptions

suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]

33 Response surface methodology

A three-dimensional surface plot and a two-dimensionalcontour

plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors

derivedfrom the statistical analysis The effects and interactions of MWenergy output and different pH levels on the removal of ammoniaare

illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under

theboiling point the maximum ammonia removal was achieved at thehighest MW energy output level The effect of pH was signi1047297cant atlow

MW

energy

output

level

as

the

ammonia

removal

ef 1047297ciencieswere

increased

with

higher

pH

With

high

MW

energy

output

theammonia removal ef 1047297ciencies of pH of 105 and 11 were relativelyclose but signi1047297cantly higher than that of pH of 10 The optimumpH

and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal

ef 1047297ciencypredicted is 763

34

Ammonia

removal

from

land 1047297ll leachate

Toachievetheoptimum

MWenergyoutput

leveltheMWprocesswith

and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from

Fig 7 Two-dimensional contour plot by response surface methodology

Fig 8 Ammonia removal from land1047297ll leachate under three different pH levels of

10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






process The inhibition of the nitri1047297cation process is reported to bedue

to

NH3 form

while

the

presence

of

NH4-N

in

the

aqueoussolution

is

reported

to

inhibit

the

NO2-N

oxidation

process

atconcentrations of 20 mgL and also begins to inhibit the NH4-Noxidation process at concentrations of 100 mgL of [NH4-N] [5]Ammonia

inhibition

effects

on

microorganisms

in

biologicaltreatments

have

also

been

reported

in

the

range

of

1500ndash5000 mgL as TAN by other researchers [1213]

For wastewaters with high ammonia concentration physicaland

chemical

methods

have

been

reported

to

exhibit

high


However

physical

and

chemical

methods

usuallycome with high cost and some other issues such as the largevolume of contaminated sludge generated from the 1047298occulationand

coagulation

approach

as

well

as

the

long

contact

time

duringthe

stripping

process

[1415]Considering cost and removal ef 1047297ciency the application of

chemicalphysical methods as a pretreatment for the highammonia

concentration

before

biological

processes

could

be

aneffective

option

The

biological

processes

require

a

proper

CN

ratioaround 201 for the aerobic treatment and 401 for the anaerobicprocess Since high ammonia levels in the leachate usually result ina

low

CN

ratio

in

the

system

the

pretreatment

could

reduce

theammonia

concentration

while

still

retaining

enough

carbon

sources for the biological process [16]Microwave (MW) radiation has been widely applied in the

environmental

1047297eld

for

the

sludge

and

wastewater

treatments

[17ndash20]

MW

enhanced

oxidation

processes

with

oxidants

such

ashydrogen peroxide (H2O2) and persulfate (S2O8

2) increased thedegradation rate of COD and some micro-pollutants such as acidorange

7

(AO7)

bromophenol

blue

phenol

and

pharmaceuticalwastewater

[21]MW radiation under high pH levels was reported to reduce

ammonia signi1047297cantly without affecting the organic compounds[22]

It

was

observed

that

when

applying

350

W

microwaveradiation the MW radiation process (below the boiling point) wasresponsible for 40 of the ammonia removal The remainingportion

of

the

dissipated

ammonia

was

removed

in

the

following

two minutes after the solution reached the boiling point by acombination of MW and thermal processes Meanwhile whenaeration process was applied concurrently with MW radiationprocess

the

contribution

of

aeration

decreased

with

longerradiation

time

However

the

continuous

boiling

process

employedin the research by Lin et al [22] could be a safety concern due to thehigh operation temperatures and may possibly generate unknownsecondary

pollutants

when

applied

to

real

land1047297ll

leachateMoreover

when

MW

radiation

has

been

used

as

a

pretreatmentapproach the high ef 1047298uent temperature can have a negative effecton the subsequent biological treatment processes

Aeration

is

another

effective

physical

treatment

for

the

removalof

ammonia

without

affecting

carbon

sources

in

the

aqueoussystem The main drawback of the aeration process is the energy

expenditure

the

need

to

raise

pH

and

the

contact

time

required[23]

Mattinen

et

al

reported

89

ammonia

reduction

at

pH

11with

24

h

contact

time

[24]

In

a

similar

research

the

maximumammonia removal ef 1047297ciency was found at 85 for a land1047297llleachate with approximately 1000 mgL ammonium nitrogen atpH

of

12

with

17

h

contact

time

[14]In

this

study

a

sequential

MW

radiation

followed

by

aerationprocess was systematically applied for ammonia removal fromaqueous phase (synthetic solution) under different MW poweroutput

pH

and

radiation

time

based

on

a

factorial

experimentaldesign

Response

surface

methodology

(RSM)

was

also

applied

toevaluate and optimize the effect of pH MW power output andradiation time For both safety and economic concerns the sampleswere

maintained

below

the

boiling

point

The

temperature

of

the

samples

was

signi1047297

cantly

increased

during

the

MW

radiation

stage and then decreased through subsequent aeration processAnd

lastly

the

MW

treatments

with

and

without

aerationprocesses

were

applied

for

the

ammonia

removal

from

a

realland1047297ll leachate

2

Material

and

methods

21 Materials and equipment

The

synthetic

solution

which

contained

2700

mgL

total

TANwas

prepared

by

dissolving

analytical

grade

ammonia

chloride(Fisher Scienti1047297c) in distilled water As mentioned above ammoniainhibitory effects in biological treatments in the range of 1500ndash5000

mgL

as

TAN

have

been

reported

[1213] As

such

it

wasdecided

to

select

an

initial

concentration

of

2700

mgL

total

TANwhich is within the inhibitory range In each test 100 mL of thefresh synthetic solution were prepared The initial pH was around57

The

pH

was

adjusted

to

the

desired

value

using

10

molL

NaOHThe

land1047297ll

leachate

was

obtained

from

a

local

land1047297ll

in

Ottawawith the initial pH 90 02 and TAN concentration of about4000 mgL

The

MW

process

was

carried

out

by

a

Panasonic

microwaveoven

(Model

NN-S

750)

with

an

operating

frequency

of

2450

MHz

and power consumption of 1320 W The maximum power outputwas 1300 W and could be adjusted from 10 to 100 in 10intervals

The

aeration

process

was

performed

using

a

Model

200

MARINApump with a total aeration rate of 110 Lh with 2 air diffusers Ineach test only one diffuser was placed in the batch reactor For thetests

carried

out

with

the

synthetic

solution

a

150

mL

beaker

wasused

as

the

batch

reactor

for

all

MW

with

and

without

aerationprocesses For the land1047297ll leachate a 1 L beaker was used as thebatch reactor for the microwave process and a 4 L glass containerwas

used

for

the

aeration

process

22 Analytical methods

TNT 832 ammonia vials from HACH Company were used to testammonia concentrations based on the Salicylate Method using aHACH DR5000 Spectrophotometer The 10 mgL ammonia nitrogenstandard

solution

from

HACH

Company

was

used

to

check

thespectrophotometer

The

pH

was

measured

using

a

glass

electrodein combination with a Fisher Accumet1Model XL25 dual channelpHion meter

23

Experimental

design

For this study MW and aeration were performed in sequenceExperimental

conditions

for

the

tests

conducted

are

summarizedin

Table

1 The

pH

range

was

selected

based

on

the

results

of

apreliminary set of experiments which was conducted to evaluate

the

effect

of

pH

on

process

ef 1047297ciency

At

a

100

power

MWradiation

times

greater

than

90

s

resulted

in

boiling

of

the

samples

Table 1

Experimental design of MW processes for the synthetic solution

MW time (s) 30 45 60 90 120

Power output level () 50 100 50 100 50 100 50 100 50 100

pH 10 U U ndash U U U U ndash U ndash

105 U U

ndash U U U U

ndash U

ndash

11 U U ndash U U U U ndash U ndash

U Experiments conducted under these conditionsndash No experiments conducted under these conditions





kept

at

10

min

for

all

samples

The

aeration

time

was

selectedbased

on

another

preliminary

set

of



pH

levels

of

10

105

11

and

10

min

of

aeration

if

applicableFig

1

presents

the

order

of

tests

carried

out

For

the

each


then

exposed

to

MW

radiation

for

the

desired

radiation

timeaccording

to

the

conditions

presented

in

Table

1 The


and

temperature

of

the

sample

were

measured

The

sample

wasaerated

10

min

and

TAN

pH

and

temperature

was

measured




to

evaluate

and

optimize

the

pH

and

MW

energy

output

forammonia

removal

from

aqueous

systems

MW

energy

output

was


X 2 (pH)

were

used

for

the

response

surface

model

and

theoutcome

response

was Y (ammonia

removal

rate)

As

shown


levels

between 1

and

1 The

ranges

of

the

individual

factorswere

chosen

from

the

preliminary

test

All

tests

were

carried

out


Statistical

analysis

was

performed

using


Y

eth THORN

frac14

C C 0C 0

100

eth1THORN

where

C

is

the

ammonia

nitrogen

concentration

after

treatmentand

C 0 is

the

initial

ammonia

nitrogen



the

optimal

operation

conditions

for

both

laboratory

andindustrial

processes

[27]

In

this

study

the

optimum


the

response

(ammonia

removal)

The

behaviour

of

the

RSM

inthis

study

was

expressed

by

the

following

second-order

polynomial

equation

[12526]

Y frac14 A0 thornXn


Xn


Xn


e eth2THORN

where

Y

is

the

response

variable

A0 is

the

value

of

the

1047297xedresponse

at

the

center

point

of

the

design

Ai

Aii

Aij

represents



of

determination

(R2)

was

used

to

describe

the

accuracyof

the

model

F

value

(Fisher

variation

ratio)

and

probability


3

Results

and

discussion


Based

on

a

preliminary

set

of

tests

a

pH

of

105

was

identi1047297ed


were

investigated

in

this

study

Two

power

output

levels

used

inthis

test

were

100

(1300

W)

and

50

(750

W)

of

the

total


E frac14 P t

1000 eth3THORN

where

E

is

the

MW

energy

output

KJ

P

is

the

power

output

W

t

isthe

MW

irradiation

time

In

order

to

test

the

ammonia

removal

at

two

power


levels

the

radiation

time

used

for

100

power

output

levelwas

half

the

radiation

time

for

50

of

the

power

output



were

obtained

by

Rabah

and

Darwish

[29]

and

Lin

et

al[22]

Also

under

the

lower

energy

output

values

the

difference


removal

ef 1047297ciencies

for

50

and

100

MW

power

outputincreases

for

higher

energy

output

levels

and

it

is

dependent

on

Fig

1


ow

chart

Table 2



1 033 0 033 1





pH

At

a

pH

of

10

higher

ammonia

removal

of

675

was

obtainedusing

100

of

the

total

MW

power

output

than

the

value

of

64using

50

MW

power

output

At

pH

levels

of

105

and

11

the

50power

output

groups

had

slightly

higher

removal

ef 1047297ciencies

thanthe

100

groups

However

for

the

MW

+

A

method

the

differences


output

tests

were

negligible

Thus

in

the

modeling

processthe

ammonia

removal

data

were

catalogued

by

the

MW


Depending

on

the

energy

output

and

pH

levels

the

MW

processcan

remove

between

109

and

531

TAN

in

the

synthetic

solutionWhen

applying

the

sequential

aeration

process

an


parameters


After

performing

63

runs

based

on

a

factorial

design

of

twoindependent

variables

the

experimental

results

for

ammonia


detect

any

outlier

and

unreliable

result

Externalstudentized

residuals

were

calculated

to

eliminate

the

outliers


using

the

collected

data

The

response

ammonia

removalpercentage

(Y )

was

predicted

by

a

second-order




X 2 is

the

adjusted

pH

value

of

the

sampleF -test

was

conducted

for

the

analysis

of

variance

(ANOVA)

toevaluate

the

statistical

signi1047297cance

of

the

quadratic

model


statistically

signi1047297cant

for

ammonia

removal

Values

of ldquoProb

gt F rdquo

less

than

005

indicate

model

terms

are

signi1047297cant

In

this

case

X 1

X 2

and

X 22 are

signi1047297cant

model

terms

For

terms

X 1 X 2

and X 21 the

corresponding

ldquoProb

gt F rdquo

values

are

larger

than

005which

implies

these

are

insigni1047297cant

terms

and

can

be


Table

3(b)

As

can

be

seen

the

reduced

model

with

F

value

of 31157 and

ldquoProb

gt

F rdquo

value

of

lt00001

indicate

that

the

reducedmodel

is

signi1047297cant

There

is

only

a

001

chance

that

the

large


value

of

4

[3031]

The

reduced

model

of

ammoniaremoval

percentage

is

shown

as

Eq

(5)

below


Coef 1047297cient

of

determination

(R2)

adjusted

R2 and

predicted

R2



in

a

model

relative

to

the

number

of

data

points

[32] Thepredicted

R2 indicates

how

well

a

regression

model

predicts

responses

for

new

observations

[33]

The

R2

value

of

0941(R2adj frac14

0937)

indicates

that

the

predicted

values

obtained

from

the

model

is

a

good

1047297t of

the

experimental

data

[29]

The


the

residual

error

to

the

pure

error

from


is

insigni1047297cant

relative

to

the

pure

error

There

is

a

54chance

that

the

lack-of-1047297t

occurs

due

to

noise

or

random


is

signi1047297cant

in

the

reduced

model

This

could

due

to

thesystematic

variations

unaccounted

for

in

the

model


relatively

low R

2

value

and

the

signi1047297cant


cansuggest

that

regression

model

fails

to

adequately

describe


R2 value

is

acceptable

with

signi1047297cant


Compared

with

the

reduced

model

the


to

be

appropriate

to

describe

the

design

due

with

a

highR2 value

of

0941

and

adequate

precision

ratio

of


ammonia

removal

Actual

values

are

collected

from

each

speci1047297crun

and

predicted

values

are

produced

by

the

model

of

Eq

(2)






Actual

P r e d i c t e d

Predicted vs Actual

20

30

40

50

60

70

80

90

20

30

40

50

60

70

80

90

Fig 3

Predicted

versus

actual

values

for

ammonia

percent

removal

Table 3


(a)



lt00001 X 1X2 5364 1 5364 388 0054

X 21 1445 1 1445 105 0311

X 22 5990 1 5990 434 0042


(b)


Model 1354655 3 4515512 31157

lt00001 Signi1047297cant X 1 1299065 1 1299065 89636

lt00001 X 2 496009

1

49601

3423

lt00001

X 22 5990 1 5990 413 0047


Pure

error

62142

51





the

predicted

values

are

good

approximations

of

the


values

The R2 value

of

0964

indicates

a

high


Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was


No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there


pattern

for all the

diagnostics

plots

graphs

and

all the





Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time







kept

at

10

min

for

all

samples

The

aeration

time

was

selectedbased

on

another

preliminary

set

of



pH

levels

of

10

105

11

and

10

min

of

aeration

if

applicableFig

1

presents

the

order

of

tests

carried

out

For

the

each


then

exposed

to

MW

radiation

for

the

desired

radiation

timeaccording

to

the

conditions

presented

in

Table

1 The


and

temperature

of

the

sample

were

measured

The

sample

wasaerated

10

min

and

TAN

pH

and

temperature

was

measured




to

evaluate

and

optimize

the

pH

and

MW

energy

output

forammonia

removal

from

aqueous

systems

MW

energy

output

was


X 2 (pH)

were

used

for

the

response

surface

model

and

theoutcome

response

was Y (ammonia

removal

rate)

As

shown


levels

between 1

and

1 The

ranges

of

the

individual

factorswere

chosen

from

the

preliminary

test

All

tests

were

carried

out


Statistical

analysis

was

performed

using


Y

eth THORN

frac14

C C 0C 0

100

eth1THORN

where

C

is

the

ammonia

nitrogen

concentration

after

treatmentand

C 0 is

the

initial

ammonia

nitrogen



the

optimal

operation

conditions

for

both

laboratory

andindustrial

processes

[27]

In

this

study

the

optimum


the

response

(ammonia

removal)

The

behaviour

of

the

RSM

inthis

study

was

expressed

by

the

following

second-order

polynomial

equation

[12526]

Y frac14 A0 thornXn


Xn


Xn


e eth2THORN

where

Y

is

the

response

variable

A0 is

the

value

of

the

1047297xedresponse

at

the

center

point

of

the

design

Ai

Aii

Aij

represents



of

determination

(R2)

was

used

to

describe

the

accuracyof

the

model

F

value

(Fisher

variation

ratio)

and

probability


3

Results

and

discussion


Based

on

a

preliminary

set

of

tests

a

pH

of

105

was

identi1047297ed


were

investigated

in

this

study

Two

power

output

levels

used

inthis

test

were

100

(1300

W)

and

50

(750

W)

of

the

total


E frac14 P t

1000 eth3THORN

where

E

is

the

MW

energy

output

KJ

P

is

the

power

output

W

t

isthe

MW

irradiation

time

In

order

to

test

the

ammonia

removal

at

two

power


levels

the

radiation

time

used

for

100

power

output

levelwas

half

the

radiation

time

for

50

of

the

power

output



were

obtained

by

Rabah

and

Darwish

[29]

and

Lin

et

al[22]

Also

under

the

lower

energy

output

values

the

difference


removal

ef 1047297ciencies

for

50

and

100

MW

power

outputincreases

for

higher

energy

output

levels

and

it

is

dependent

on

Fig

1


ow

chart

Table 2



1 033 0 033 1





pH

At

a

pH

of

10

higher

ammonia

removal

of

675

was

obtainedusing

100

of

the

total

MW

power

output

than

the

value

of

64using

50

MW

power

output

At

pH

levels

of

105

and

11

the

50power

output

groups

had

slightly

higher

removal

ef 1047297ciencies

thanthe

100

groups

However

for

the

MW

+

A

method

the

differences


output

tests

were

negligible

Thus

in

the

modeling

processthe

ammonia

removal

data

were

catalogued

by

the

MW


Depending

on

the

energy

output

and

pH

levels

the

MW

processcan

remove

between

109

and

531

TAN

in

the

synthetic

solutionWhen

applying

the

sequential

aeration

process

an


parameters


After

performing

63

runs

based

on

a

factorial

design

of

twoindependent

variables

the

experimental

results

for

ammonia


detect

any

outlier

and

unreliable

result

Externalstudentized

residuals

were

calculated

to

eliminate

the

outliers


using

the

collected

data

The

response

ammonia

removalpercentage

(Y )

was

predicted

by

a

second-order




X 2 is

the

adjusted

pH

value

of

the

sampleF -test

was

conducted

for

the

analysis

of

variance

(ANOVA)

toevaluate

the

statistical

signi1047297cance

of

the

quadratic

model


statistically

signi1047297cant

for

ammonia

removal

Values

of ldquoProb

gt F rdquo

less

than

005

indicate

model

terms

are

signi1047297cant

In

this

case

X 1

X 2

and

X 22 are

signi1047297cant

model

terms

For

terms

X 1 X 2

and X 21 the

corresponding

ldquoProb

gt F rdquo

values

are

larger

than

005which

implies

these

are

insigni1047297cant

terms

and

can

be


Table

3(b)

As

can

be

seen

the

reduced

model

with

F

value

of 31157 and

ldquoProb

gt

F rdquo

value

of

lt00001

indicate

that

the

reducedmodel

is

signi1047297cant

There

is

only

a

001

chance

that

the

large


value

of

4

[3031]

The

reduced

model

of

ammoniaremoval

percentage

is

shown

as

Eq

(5)

below


Coef 1047297cient

of

determination

(R2)

adjusted

R2 and

predicted

R2



in

a

model

relative

to

the

number

of

data

points

[32] Thepredicted

R2 indicates

how

well

a

regression

model

predicts

responses

for

new

observations

[33]

The

R2

value

of

0941(R2adj frac14

0937)

indicates

that

the

predicted

values

obtained

from

the

model

is

a

good

1047297t of

the

experimental

data

[29]

The


the

residual

error

to

the

pure

error

from


is

insigni1047297cant

relative

to

the

pure

error

There

is

a

54chance

that

the

lack-of-1047297t

occurs

due

to

noise

or

random


is

signi1047297cant

in

the

reduced

model

This

could

due

to

thesystematic

variations

unaccounted

for

in

the

model


relatively

low R

2

value

and

the

signi1047297cant


cansuggest

that

regression

model

fails

to

adequately

describe


R2 value

is

acceptable

with

signi1047297cant


Compared

with

the

reduced

model

the


to

be

appropriate

to

describe

the

design

due

with

a

highR2 value

of

0941

and

adequate

precision

ratio

of


ammonia

removal

Actual

values

are

collected

from

each

speci1047297crun

and

predicted

values

are

produced

by

the

model

of

Eq

(2)






Actual

P r e d i c t e d

Predicted vs Actual

20

30

40

50

60

70

80

90

20

30

40

50

60

70

80

90

Fig 3

Predicted

versus

actual

values

for

ammonia

percent

removal

Table 3


(a)



lt00001 X 1X2 5364 1 5364 388 0054

X 21 1445 1 1445 105 0311

X 22 5990 1 5990 434 0042


(b)


Model 1354655 3 4515512 31157

lt00001 Signi1047297cant X 1 1299065 1 1299065 89636

lt00001 X 2 496009

1

49601

3423

lt00001

X 22 5990 1 5990 413 0047


Pure

error

62142

51





the

predicted

values

are

good

approximations

of

the


values

The R2 value

of

0964

indicates

a

high


Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was


No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there


pattern

for all the

diagnostics

plots

graphs

and

all the





Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






pH

At

a

pH

of

10

higher

ammonia

removal

of

675

was

obtainedusing

100

of

the

total

MW

power

output

than

the

value

of

64using

50

MW

power

output

At

pH

levels

of

105

and

11

the

50power

output

groups

had

slightly

higher

removal

ef 1047297ciencies

thanthe

100

groups

However

for

the

MW

+

A

method

the

differences


output

tests

were

negligible

Thus

in

the

modeling

processthe

ammonia

removal

data

were

catalogued

by

the

MW


Depending

on

the

energy

output

and

pH

levels

the

MW

processcan

remove

between

109

and

531

TAN

in

the

synthetic

solutionWhen

applying

the

sequential

aeration

process

an


parameters


After

performing

63

runs

based

on

a

factorial

design

of

twoindependent

variables

the

experimental

results

for

ammonia


detect

any

outlier

and

unreliable

result

Externalstudentized

residuals

were

calculated

to

eliminate

the

outliers


using

the

collected

data

The

response

ammonia

removalpercentage

(Y )

was

predicted

by

a

second-order




X 2 is

the

adjusted

pH

value

of

the

sampleF -test

was

conducted

for

the

analysis

of

variance

(ANOVA)

toevaluate

the

statistical

signi1047297cance

of

the

quadratic

model


statistically

signi1047297cant

for

ammonia

removal

Values

of ldquoProb

gt F rdquo

less

than

005

indicate

model

terms

are

signi1047297cant

In

this

case

X 1

X 2

and

X 22 are

signi1047297cant

model

terms

For

terms

X 1 X 2

and X 21 the

corresponding

ldquoProb

gt F rdquo

values

are

larger

than

005which

implies

these

are

insigni1047297cant

terms

and

can

be


Table

3(b)

As

can

be

seen

the

reduced

model

with

F

value

of 31157 and

ldquoProb

gt

F rdquo

value

of

lt00001

indicate

that

the

reducedmodel

is

signi1047297cant

There

is

only

a

001

chance

that

the

large


value

of

4

[3031]

The

reduced

model

of

ammoniaremoval

percentage

is

shown

as

Eq

(5)

below


Coef 1047297cient

of

determination

(R2)

adjusted

R2 and

predicted

R2



in

a

model

relative

to

the

number

of

data

points

[32] Thepredicted

R2 indicates

how

well

a

regression

model

predicts

responses

for

new

observations

[33]

The

R2

value

of

0941(R2adj frac14

0937)

indicates

that

the

predicted

values

obtained

from

the

model

is

a

good

1047297t of

the

experimental

data

[29]

The


the

residual

error

to

the

pure

error

from


is

insigni1047297cant

relative

to

the

pure

error

There

is

a

54chance

that

the

lack-of-1047297t

occurs

due

to

noise

or

random


is

signi1047297cant

in

the

reduced

model

This

could

due

to

thesystematic

variations

unaccounted

for

in

the

model


relatively

low R

2

value

and

the

signi1047297cant


cansuggest

that

regression

model

fails

to

adequately

describe


R2 value

is

acceptable

with

signi1047297cant


Compared

with

the

reduced

model

the


to

be

appropriate

to

describe

the

design

due

with

a

highR2 value

of

0941

and

adequate

precision

ratio

of


ammonia

removal

Actual

values

are

collected

from

each

speci1047297crun

and

predicted

values

are

produced

by

the

model

of

Eq

(2)






Actual

P r e d i c t e d

Predicted vs Actual

20

30

40

50

60

70

80

90

20

30

40

50

60

70

80

90

Fig 3

Predicted

versus

actual

values

for

ammonia

percent

removal

Table 3


(a)



lt00001 X 1X2 5364 1 5364 388 0054

X 21 1445 1 1445 105 0311

X 22 5990 1 5990 434 0042


(b)


Model 1354655 3 4515512 31157

lt00001 Signi1047297cant X 1 1299065 1 1299065 89636

lt00001 X 2 496009

1

49601

3423

lt00001

X 22 5990 1 5990 413 0047


Pure

error

62142

51





the

predicted

values

are

good

approximations

of

the


values

The R2 value

of

0964

indicates

a

high


Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was


No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there


pattern

for all the

diagnostics

plots

graphs

and

all the





Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






Actual

P r e d i c t e d

Predicted vs Actual

20

30

40

50

60

70

80

90

20

30

40

50

60

70

80

90

Fig 3

Predicted

versus

actual

values

for

ammonia

percent

removal

Table 3


(a)



lt00001 X 1X2 5364 1 5364 388 0054

X 21 1445 1 1445 105 0311

X 22 5990 1 5990 434 0042


(b)


Model 1354655 3 4515512 31157

lt00001 Signi1047297cant X 1 1299065 1 1299065 89636

lt00001 X 2 496009

1

49601

3423

lt00001

X 22 5990 1 5990 413 0047


Pure

error

62142

51





the

predicted

values

are

good

approximations

of

the


values

The R2 value

of

0964

indicates

a

high


Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was


No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there


pattern

for all the

diagnostics

plots

graphs

and

all the





Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






the

predicted

values

are

good

approximations

of

the


values

The R2 value

of

0964

indicates

a

high


Fig

4

showsthe

diagnostics

plots

of

externally

studentizedresidual

versus

predicted

value run

pH

and

time

Outliers

in thediagnostics

plots

simply

indicate the

magnitude

of

the

residuals

determining

if

any

of

the

data had

particularly

large

residuals[39]

As

shown

in

the

diagnostics

plots

the

red

line was


No

outlier exists

in

the

plot

indicating that

the

model isconsistent

with

all the

data

Furthermore

there


pattern

for all the

diagnostics

plots

graphs

and

all the





Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






Fig 5

Normal

probability

of

externally

studentized

residuals

for

ammonia

removal





externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time






externally


randomly

scattered

acrossthe

graph

Thus

there

is no

violation

of

the

independence

orconstant

variance assumption

for all runs

[28]

Fig

5

presents

anadequate

1047297t of

the

externally

studentized

residuals


percentage

con1047297rming

that

the


suit

the

analytical data The

residuals

arenormally

distributed

if the

points on

the

plot

follow

a

straightline

[40]



plot

are

illustrated

in

Figs

6

and

7

respectively

to

providea

better

visualization

of

the

statistically

signi1047297cant

factors


illustrated

in

both

1047297gures

It

can

be

seen

that

the

MW

energyoutput

had

a

positive

effect

for

the

ammonia

removal

all

the

timeSince

the

samples

in

the

batch

test

were

maintained

under


MW

energy

output

level

as

the

ammonia

removal


increased

with

higher

pH

With

high

MW

energy

output


and

MW

energy

output

for

ammonia

removal

were

found

to

be11

and

78

KJ

and

the

maximum

ammonia

removal


34

Ammonia

removal

from


Toachievetheoptimum

MWenergyoutput


and

without

aeration

using

50

of

the

totalpower

output

with120

s

radiation

time

was

applied

to the

leachate

sample

Three

pHlevels of

10

105

and

11

were investigated

in

the

course

of

thisresearch

Fig

8

shows

the

ammonia

removal

ef 1047297ciency

for


at

three

different

pH

levels of

10

105

and

11

using 50

of total

MWoutput

for

120

s

MWradiation

time

The

ammonia


for

both

MW

and

MW

+

A

methods

increased

withtheincrease

of

pH

This

is

a

similar

trend

to the

result

obtained

from



10 105

and

11

using

50

of

total

MW

output

for

120

s

MW irradiation

time




statistical analysis and optimization of ammonia removal from landfill leachate by sequential...

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