solid waste in wastewater

KATHMANDU UNIVERSITY

DHULIKHEL, KAVRE

Solids in Wastewater

By

Nirmal Kumar Shahi

Bachelor of Technology in Environmental Engineering

To

D. Eng. Nawa Raj Khatiwada, Asso. Prof.

Department of Environmental Science and Engineering

Solids in Wastewater

The term “solids” is generally used when referring to any material suspended or dissolved in

wastewater that can be physically isolated either through filtration or through evaporation. Solids

may affect water or effluent quality adversely in a number of ways. Waters with high dissolved

solids generally are of inferior palatability and may induce an unfavorable physiological reaction

in the transient consumer. For these reasons, a limit of 500 mg dissolved solids/L is desirable for

drinking waters. Highly mineralized waters also are unsuitable for many industrial applications.

Waters high in suspended solids may be esthetically unsatisfactory for such purposes as bathing.

Solids analyses are important in the control of biological and physical wastewater treatment

processes and for assessing compliance with regulatory agency wastewater effluent limitations.

Solids can be classified as either filterable or nonfilterable. Filterable solids may either be

settleable or nonsettleable. Solids can also be classified as organic or inorganic.

Organic Solids

In domestic wastewater, solids are about 50 percent organic. This fraction is generally of animal

or vegetable life, dead animal matter, plant tissue or organisms, but may also include synthetic

(artificial) organic compounds. These are substances which contain carbon, hydrogen and

oxygen, some of which may be combined with nitrogen, sulfur or phosphorous. The principal

organic compounds present in domestic wastewater are proteins, carbohydrates and fats together

with the products of their decomposition. These compounds are subject to decay or

decomposition through the activity of bacteria and other living organisms and are combustible,

that is, they can be ignited or burned. Since the organic fraction can be drive off at high

temperatures, they are sometimes called volatile solids.

Inorganic Solids

Inorganic solids are substances that are inert and not subject to decay. Exceptions to this

characteristic are certain mineral compounds or salts, such as sulfates which under certain

conditions can be broken down. Inorganic solids are frequently called mineral substances and

include sand, gravel and silt as well as the mineral salts in the water supply which produce the

hardness and mineral content of the water. In general, they are non-combustible.

Solids can also be grouped depending on their physical state as suspended solids, colloidal solids

and dissolved solids, each of which can include both organic and inorganic solids.

Settleable Solids

Objective

To determine the amount of settleable solids in wastewater.

Apparatus Required

Graduate Cylinder instead of Imhoff Cone

Stirring glass rod

Theory

Settleable solids are that portion of the suspended solids which are of sufficient size and weight

to settle in a given period of time, usually one hour. There are those which will settle in an

Imhoff Cone in one hour but we used graduate cylinder instead of it. The method use for

determination of settleable solids is volumetric. The results are reported as milliliter of settled

solids per liter of wastewater (volume/volume basis). Settleable solids are approximately 75 %

organic and 25 % inorganic.

Settleable Solids =

LmL

LVmeSampleVolu

vSolidsSettleable/

,

Procedure

Procedure that we had employed was according to Standard Methods, Section 2540 F,

Volumetric Method.

Sample was well mixed and poured into graduate cylinder up to 1-L mark.

Then was allowed to settle for 45 minutes.

Side of the cylinder was gently stirred by spinning the cone.

Sample was then allowed to settle for additional 15 minutes.

Volume of settleable solid was then measured with the help of measuring cylinder and

recorded.

Calculation

Sample Volume (V) = 1L

Volume of settleable solids (v) =6mL

Settleable Solids =

LmL

L

mL

LVmeSampleVolu

vSolidsSettleable/6

1

6

,

Result and Conclusion

Thus from above amount of settleable solids in wastewater is 6mL/L. During laboratory

experiment, the sample was not well mixed and taken directly from the jar due to which the

value of result we obtained may be high or less.

Precaution

Use resistant-glass or plastic bottles, provided that the material in suspension does not

adhere to container walls.

Sample should be well mix.

Total Solids

Objective

To determine the amount of total solids in sample wastewater.

Apparatus Required

Evaporating dishes, 100 mL capacity

Drying oven, for operation at 98 and 103-105°C

Desiccator, with indicating desiccant

100 mL graduated cylinders

Analytical Balance

Theory

Total solids, as the term implies, includes all of the solid constituents of a wastewater. Total

solids are the total of the organic and inorganic solids or the total of the suspended and dissolved

solids. In an average domestic wastewater, total solids are about half organic and half inorganic,

and about two-thirds in solution (dissolved) and one-third in suspension. The organic solids,

which are subject to decay, constitute the main problem in wastewater treatment.

„„Total solids‟‟ is the term applied to the material residue left in the vessel after evaporation of a

sample and its subsequent drying in an oven at a defined temperature. Total solids includes

„„total suspended solids,‟‟ the portion of total solids retained by a filter, and „„total dissolved

solids,‟‟ the portion that passes through the filter.

Total Solids = )/(,

1000)(LmgTS

mLmeSampleVolu

AB

Where,

A = Weight of Dish, mg

B = Weight of Dish + Dried Residue, mg

Procedure Procedure we had employed was accordance with Standard Method, Section 2540 B., Total

Solids Dried at 1030-105

0 C.

Before keeping the sample into oven, it was turned on and temperature was adjusted to

1030 C-105

0 C.

Evaporating dish was then heated for 5 minutes in the oven and then placed in desiccator

to cool.

Immediately before using the cooled dish it was weighed and noted.

Sample to be measure was well mixed and measured into a graduated cylinder of 50 mL

volume and transferred/poured to the evaporating dish.

Sample was evaporated to dryness in an oven at 1030 C-105

0 C.

Dish was then removed from drying oven and kept in desiccator to room temperature.

Dish with residue was weighed and recorded.

Observation and Calculation

Sample Volume =50mL

Weight of Dish, mg (A) =50.315g

Weight of Dish + Dried Residue, mg (B) =50.641g

Total Solids (TS) = mL

L

mL

g

mgg

mLmeSampleVolu

AB

50

10001000)315.50641.50(

,

1000)(

= 6520


Therefore, the value of total solids in the given sample of wastewater was found to be 6520

mg/L. The value thus obtained is too higher than that of the threshold value of the portable

drinking water. This is due to high concentration of settleable solids and the water was turbid.

Precaution

Sample to be measure should be well mix.



Samples need to be measured accurately, weighed carefully, and dried and cooled

completely.

Regular checking of oven temperature should be done to maintain the desired

temperature range.

Suspended Solids

Objective

To determine the amount of suspended solids in wastewater.

Apparatus Required

Filtration apparatus

Glass fiber filters

Filter flasks

Graduate Cylinder

Vacuum pump

Drying oven, for operation at 1030 C-105

0 C

Analytical balance

Desiccator

Theory Suspended solids are those which are visible and in suspension in the water. They are the solids

which can be removed from the wastewater by physical or mechanical means, such as

sedimentation or filtration. More precisely, they are the solids which are retained on the filter

mat or glass fiber pad in a Gooch Crucible. Suspended solids will include the larger floating

particles and consist of sand, grit, clay, fecal solids, paper, pieces of wood, particles of food and

garbage, and similar materials. Suspended solids are approximately 70 percent organic solids

and 30 percent inorganic solids, the latter being principally sand and grit. The suspended solids

portion consists of settleable solids and colloidal solids.

A well-mixed measured sample is poured into a filtration apparatus and, with the aid of a

vacuum pump or aspirator, drawn through a pre-weighed standard laboratory glass fiber filter.

After filtration, the glass fiber filter is dried at 103-105°C, cooled, and reweighed. The increase

in weight of the filter and solids compared to the filter alone represents the total suspended solids

(TSS).

Total Suspended Solids = )/(,

1000)(LmgTSS

mLmeSampleVolu

CD

Where,

C = Weight of Dish + Filter, mg

D = Weight of Dish + Filter + Dried Residue, mg

Procedure

The procedure we had employed is in accordance with Standard Methods, Section 2540 D., Total

Suspended Solid Dried at 1030

C-1050 C.

Before taking measurement dish and filter were weighed and then filtration apparatus was

placed/mounted with weighed filter.

Sample was well mixed and poured into a graduate cylinder to the 50 mL.

Before pouring the sample into the filtration apparatus, suction was applied and filter was

seat with a small amount of distilled water.

Selected volume of sample was poured into filtration apparatus and sample was drawn

through filter into filtration flask.

Filter was dried in an oven at 1030

C-1050 C for at least 1 hour and cooled in desiccator

to room temperature and weighed.


Sample Volume = 50 mL

Weight of Dish + Filter, mg (C) = 20.617 g

Weight of Dish + Filter + Dried Residue, mg (D) = 20.890 g

Total Suspended Solids (TSS) =mL

L

mL

g

mgg

mLmeSampleVolu

CD

50

10001000)617.20890.20(

,

1000)(

= 5460


Thus the result found out for suspended solid was 5460mg/L which is too higher than other

values. This may be due to some handling problems due to which the value is totally distorted

from real value. After the collection of the sample there need to analyze as soon as possible.

Precaution





completely.


temperature range.

Dissolved Solids

Objective

To determine the amount of dissolved solids in wastewater.

Apparatus Required

Evaporating dish, 100 mL capacity constructed from porcelain

Drying oven, operating at 1030 C-105

0 C

Desiccator

Graduate cylinder

Analytical Balance

Filter Paper (0.45µm)

Filtration apparatus

Vacuum pump

Crucible

Theory

Dissolved solids are smaller in size than suspended and colloidal solids. As used, the term

means all of the solids which pass through the filter with a 2.0 µm or smaller nominal average

pore size. Of the total dissolved solids, about 90 percent are in true solution and about 10

percent colloidal. Dissolved solids, as a whole, are about 40 percent organic and 60 percent

inorganic. In portable waters, most of the matter is in dissolved form and consists mainly of

inorganic salts, small amounts of organic matter, and dissolved gases. The total dissolved solids

content of portable waters usually ranges from 20 to 1000 mg/L, and, as a rule, hardness

increases with total dissolved solids.

Total Dissolve Solids (TDS) = LmgmLmeSampleVolu

AB/

,

1000)(

Where,

A = Weight of Dish, mg

B = Weight of Dish + Dried Residue, mg

Procedure

Before keeping the sample into oven, it was turned on and temperature was adjusted to

1030 C-105

0 C.

Evaporating dish was then heated for 5 minutes in the oven and then placed in desiccator

to cool.

Immediately before using the cooled dish it was weighed and noted.

Filtration apparatus was placed/mounted with weighed filter.






Sample collected in the filtration flask was transferred to evaporating dish and kept in

drying oven.

Sample was evaporated to dryness in an oven at 1030 C-105

0 C.

Dish was then removed from drying oven and kept in desiccator to room temperature.

Dish with residue was weighed and recorded.


Volume of sample = 50 mL

Weight of Beaker (A) = 48.430g

Weight of Beaker + Dried Residue (B) = 48.495g

Total Dissolve Solids (TDS) = mL

L

mL

g

mgg

mLmeSampleVolu

AB

50

10001000)430.48495.48(

,

1000)(

= 1300

Results and Conclusion

The dissolved solid was found out to be 1300 mg/L, when the value of suspended and dissolved

solids are added the result obtained is around the value that we obtained for total solid. But there

is difference of 240 mg/L, this may be due to some errors like instrumental error or manual

procedures like weighing error, splashing water. During the experiment, the filter paper was

burned out due to high heat, thus this may have cause error and it was major issue for achieving

the accurate result.

Precaution





completely.


temperature range.

Volatile and Fixed Suspended Solids

Objective

To determine the amount of volatile and fixed suspended solids in wastewater.

Apparatus Required

Muffle furnace, capable of operating at 550 +/- 500 C

Ceramic dish

Insulated gloves

Theory

One of the major objectives of preforming solids determination upon domestic wastewater,

industrial wastewater, and sludge sample is to obtain a measure of the amount of organic matter

present. This test is accomplished by a combustion procedure in which organic matter is

converted to gaseous carbon dioxide and water, and thus volatilized, while the temperature is

controlled to prevent decomposition and volatilization of in organic substances as much as is

consistent with complete oxidation of the organic matter.

The standard procedure to volatile-solids analysis is to conduct ignitions at 550 +/- 500 C. It is

about the lowest temperature at which organic matter, particularly carbon residues resulting from

pyrolysis of carbohydrates and other organic matter, as shown below can be oxidized to

reasonable speed. Also at 550 +/- 500 C decomposition of inorganic salts is minimized.

Cx(H2O)y → xC + yH2O

C + O2 →CO2

Solids remaining after the analysis for total solids, total dissolved solids or total suspended solids

are ignited at 550 +/- 500 C to a constant weight. The results are called Total Volatile Solids

(TVS), Dissolved Volatile Solids (DVS) and Total Volatile Suspended Solids (TVSS). The

weight loss as a result of the ignition represents the volatile portion of the solids. The difference

in weight of the ash and support vessel remaining after ignition compared to the empty vessel

represents the fixed solids.

Procedure

The procedure we had employed is in accordance with Standard Methods, Section 2540 E.,

Fixed and Volatile Solids Ignited at 5500 C.








Filter with evaporating dish was dried in an oven at 1030

C-1050 C for at least 1 hour and

transferred to Muffle furnace which was at a temperature of 550 +/- 500 C and kept for

15 to 20 minutes until ignition of solid was completed

Then cooled in desiccator to room temperature and weighed.


Sample Volume = 50mL

Weight of Filter Paper = 0.486g

Weight of Dish + Filter + Residue, (C) = 20.617g

During experiment, when dish and filter paper with residue was kept in Muffle Furnace filter

paper was burned, thus we subtract the weight of filter paper.

Weight of Dish + Dried Residue before Ignition, mg (E) = (20.617-0.486) g = 20.131 g

Weight of Dish + Dried Residue after Ignition, mg (F) = 19.967g

Volatile Suspended Solids (VSS) =mL

L

mL

g

mgg

mLmeSampleVolu

FE

50

10001000)967.19131.20(

,

1000)(

= 3280

Fixed Suspended Solids (FSS) = Total Suspended Solids (TSS) – Volatile Suspended Solids

(VSS)

= (5460-3280) = 2180

Result and Conclusion From above experiment the value of fixed suspended solid was found out to be 2180 mg/L and

volatile suspended solid 3280 mg/L. Again the value obtained was too higher than that other

values, this may due to some handling errors and instrumental errors.

Precaution Sample to be measure should be well mix.




completely.


temperature range.

Volatile and Fixed Dissolved Solids

Objective

To determine the amount of volatile and fixed dissolved solids in wastewater.

Apparatus Required Muffle furnace, capable of operating at 550 +/- 50

0 C

Ceramic dish

Insulated gloves

Theory

One of the major objectives of preforming solids determination upon domestic wastewater,

industrial wastewater, and sludge sample is to obtain a measure of the amount of organic matter

present. This test is accomplished by a combustion procedure in which organic matter is

converted to gaseous carbon dioxide and water, and thus volatilized, while the temperature is

controlled to prevent decomposition and volatilization of in organic substances as much as is

consistent with complete oxidation of the organic matter.

The standard procedure to volatile-solids analysis is to conduct ignitions at 550 +/- 500 C. It is

about the lowest temperature at which organic matter, particularly carbon residues resulting from

pyrolysis of carbohydrates and other organic matter, as shown below can be oxidized to

reasonable speed. Also at 550 +/- 500 C decomposition of inorganic salts is minimized.

Cx(H2O)y → xC + yH2O

C + O2 →CO2

Solids remaining after the analysis for total solids, total dissolved solids or total suspended solids

are ignited at 550 +/- 500 C to a constant weight. The results are called Total Volatile Solids

(TVS), Dissolved Volatile Solids (DVS) and Total Volatile Suspended Solids (TVSS). The

weight loss as a result of the ignition represents the volatile portion of the solids. The difference

in weight of the ash and support vessel remaining after ignition compared to the empty vessel

represents the fixed solids.

Procedure

The procedure we had employed is in accordance with Standard Methods, Section 2540 E.,

Fixed and Volatile Solids Ignited at 5500 C.

Before taking measurement dish was weighed and then filtration apparatus was







Sample collected into filtration flask was then poured into evaporating dish and dried in

an oven at 1030

C-1050 C for at least 1 hour and transferred to Muffle furnace which was

at a temperature of 550 +/- 500 C and kept for 15 to 20 minutes until ignition of solid was

completed

Then cooled in desiccator to room temperature and weighed.


Sample Volume = 50 mL

Weight of Beaker = 48.43g

Weight of Dish + Dried Residue before Ignition, mg (E) = 48.495g

Since we used beaker instead of dish due to lack of it so we were unable to put beaker into

Muffle Furnace, thus we assumed 60% volatile dissolved solid and 40% fixed dissolved solid .

Volatile Dissolved Solids (VDS) =

= 780

Fixed Dissolved Solids (FDS) = Total Dissolved Solids (TDS) – Volatile Dissolved Solids

(VDS) = (1300-780)

= 520

Result and Conclusion Thus the result obtained for volatile and fixed dissolved solid was 780mg/L and 520 mg/L. Thus

the result obtained is equal to the value of total dissolved solid i.e. 1300 mg/L

Precaution Sample to be measure should be well mix.




completely.


temperature range.

ERROR CALCULATION

The total solid (TS)= TDS+TSS

Where Total Solid (TS)= 6520 mg/L and

TDS+TSS = 6760 mg/L

Therefore,

% ERROR=

= 3.68%

This error may be due to some personal, instrumental, and other irregularities while conducting

the experiment.

Sludge Volume Index Objective To determine the sludge volume index (SVI) of wastewater.

Apparatus Required

Graduate Cylinder of 1-L and 50 mL volume

Evaporating Dish

Filtration Apparatus

Filter paper

Vacuum pump

Drying oven, for operation at 1030 C-105

0 C

Analytical balance

Desiccator

Filtration Flask

Theory

The sludge volume index (SVI) is the volume in millimeters occupied by 1g of a suspension after

30 minute settling. SVI typically is used to monitor settling characteristics of activated sludge

and other biological suspensions. It is a very important indicator that determines our control or

rate of desludging on how much sludge is to be returned to the aeration basin and how much to

take it out from the system. Value of sludge volume index can be calculated as following:

SVI =

( )

Procedure

For Settleable Solids

Sample was well mixed and poured into graduate cylinder up to 1-L mark.

Then was allowed to settle for 30 minutes.

Side of the cylinder was gently stirred by spinning the cone.

Sample was then allowed to settle for additional 15 minutes.

Volume of settleable solid was then measured with the help of measuring cylinder and

recorded.

For MLSS








Filter was dried in an oven at 1030

C-1050 C for at least 1 hour and cooled in desiccator

to room temperature and weighed and noted.


Volume of settled solids (SV) = 6

Mixed Liquor Suspended Solids (MLSS) = 5460

Sludge Volume Index (SVI) =

=

= 1.098 mL/mg


Thus from the above experiment the result obtained for Sludge Volume Index was 1.098 mL/mg.

SVI can indicate changes occurring in the activated sludge treatment process. By trending SVI

data over a period of time, operators are able to prevent problems. SVI = 80 mL/g or less. This

usually indicates a sludge that is dense and has rapid settling characteristics. This is most often

attributed to an old, over-oxidized sludge typically seen in an extended aeration facility. The floc

particles would be dense and granular in appearance (like a BB). As this type of sludge settles, it

may leave a cloudy appearance in the supernate above the settled sludge blanket. This turbidity is

called pinpoint floc (pin-floc). The sludge usually begins settling quickly after the start of the

sludge settleability test, and it does not form larger particles before settling. Effluent BOD results

may be below requirements, but TSS levels can still be high. And

Precaution





completely.


temperature range.

Reference:

McCarty, P. L; Parkin, G.F; Sawyer, C. N; (2003) Chemistry for Environmental Engineering

and Science 5th

edition, TATA McGra-Hill, Delhi

solid waste in wastewater

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