ert 417/4 waste treatment in bioprocess industry sem 1 (2010/2011) ‘physical treatment processes...

ERT 417/4 WASTE TREATMENT IN

BIOPROCESS INDUSTRYSEM 1 (2010/2011)

‘Physical Treatment Processes of

Industrial Waste’(Part A)By; Mrs Hafiza Binti Shukor

INTERPRET, COMPARE, JUSTIFY and CHOOSE the physical treatment methods for waste treatment in industries.

CALCULATE and DESIGN the basic structure of waste treatment unit operations

By; Mrs Hafiza Binti Shukor

At the end of these topic, students should be able to acquire these ability:

ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRYSEM 1 (2010/2011)

INTRODUCTION OF WASTEWATER TREATMENT PLANT DESIGN

TERTIARY PROCESS

PRIMARY PROCESS

SECONDARY PROCESS

Wastewater

Bar Rack

Grit Chamber

Equalization Basin

Primary Settling

Biological Treatment

Secondary Settling

Advance Wastewater Treatment

PRETREATMENT PROCESS


PRETREATMENT PROCESS

Objectives:Protection to the WWTP equipmentSeldom used in industrial WWTP

( Several devices/structures are placed UPSTREAM to the PRIMARY TREATMENT)

Pretreatment Devices/structures:1) BAR RACKS

• remove large object that would damage @ foul pumps, valves and other mechanical equipment

• Eg. Rags, logs, paper, plastics, rocks and leaves.


Consists of a series of parallel bars or a perforated screen placed in a channel. The flow passes through the screen and the large solids are trapped on the bars for removal. The bar screen may be coarse (2-4 inch openings) or fine (0.75-2.0 inch openings). The bar screen may be manually cleaned or mechanically cleaned (performed frequently enough to prevent solids buildup and reduce flow into the plant)

Fig. 1 : Bar Screen / Bar Rack


2) GRIT CHAMBER• Remove grit-inert, dense materials that tends to settle in

corners, bends, reducing flow capacity and ultimately clogging pipes and channels

• Eg. Sand, broken glass, silt, etcTo remove the heavy inorganic solids, which could cause excessive mechanical wear. Grit includes sand, gravel, clay, egg shells, coffee grounds, metal filings, seeds and other similar materials. There are several devices or processes used for grit removal. All of the processes are based on the fact that grit is heavier than the organic solids that should be kept in suspension for subsequent treatment. Grit removal processes use gravity/velocity, aeration or centrifugal force to separate the solids from the wastewater.


Pretreatment Devices/structures (continue……):3) COMMINUTION

• Devices that can CHOP UP wastewater solids by revolving cutting bars

• It placed downstream of the GRIT CHAMBER to protect the cutting bars from abrasion

• Cutting from the communitor are returned directly to the wastewater Its reduce solids to a size that can enter

the plant without causing mechanical problems or clogging. In this device all of the wastewater flow passes through the grinder assembly. The grinder consists of a screen or slotted basket, a rotating or oscillating cutter and a stationary cutter.Solids pass through the screen and are chopped or shredded between the two cutters. The comminutor will not remove solids that are too large to fit through the slots, and it will not remove floating objects. The materials must be removed manually


Pretreatment Devices/structures (continue……):

4) FLOW EQUALIZATION• To minimize fluctuations in WW characteristics in order

to provide optimum conditions for subsequence process• To provide adequate dampening of organic fluctuations

in order to prevent shock loading to biological system• Provide adequate pH control • Provide cont. feed to biological system• Provide capacity for controlled discharge• To prevent high conc. of toxic materials from entering

the biological treatment plants.

Bar Screen / communi

tor

Grit Removal

Equalization Basin

Primary Treatmen

t

Effluent for further treatment

Q

t

Q

t


Flow diagram of a typical preliminary treatment /

pretreatment system

Sump & Pump House

Bar Screen

(screenings)

Grit Chamber

(grits)

Skimming Tank (oil &

grease)

Effluent for discharge or further treatment


PRIMARY PROCESS

Objectives:Prepare WW for biological treatment (stabilize organic)Remove + 60% SS and 35% BOD5 in sewage

( primary & secondary process handle MOST of the NON-TOXIC wastewater)

Devices/structures:• Sedimentation , accelerated gravity separation,

floatation, filtration, gas stripping, chemical precipitation, adsorption etc.

• Remove by settling @ floating • Oil, gas and suspended solid are removed by floatation,

sedimentation and filtration.• Also neutralization process and equalization process (no

fluctuation/ variation in flow and concentration of WW)


SECONDRY PROCESS

Objectives:Speed up natural process of breaking down biodegradable organicsRemove up to 85 % SS and BOD5

Devices/structures:• Activated sludge, extended aeration, rotating biological

contacting (RBC), trickling filter, aerated lagoons, sequencing batch reactor etc

• Biological degradation of soluble organics.• Mostly aerobically in an open aerated vessels @ lagoon• Speed up natural processes of breaking down

biodegradable organics• Cannot remove N, P, heavy metals, pathogens, bacteria

and viruses.• After treatment, microorganism and other carried over

solids are allowed to settle.• A fraction of sludge is recycle• Excess sludge along with sediment solids has to be

disposed off.


TERTIARY / ADVANCED PROCESS

Objectives:Nutrients removal, chlorination and dechlorinationProcess added after biological treatment in order to remove specific group/ types of residualCan remove + 95% BOD5, P, SS, bacteria and N

Devices/structures:• Filtration –removes SS• Granular Activated Carbon – removes organics• Chemical oxidation – removes oxidizable organics

• Expensive to process LARGE VOLUME of WW• Such a polishing process


SELECTION OF TREATMENT PROCESS

Depends on the degree of treatment required to bring the quality of raw wastewater to a permissible level of treated wastewater (eg. Effluent from the treatment plant)

This ensures that the final effluent is either safe for disposal or acceptable for specific reuse or recycling.

Other significant factor that will influence the selection of a treatment system are as follows:Availability of funds and land at the treatment siteThe topography of land at the treatment siteNon-availability of suitable mechanical equipment and skilled personnel for running and maintaining the plant.


SELECTION OF TRATMENT PROCESS cont…

The points to keep in mind while selecting the treatment process are as follows:1.Reduction of inorganic material component of wastewater is much easier and cheaper than removal of organics contents of wastewater2.Removal of suspended solids from wastewater requires lesser time and efforts than of colloidal and dissolved solids3.In many countries, the Environmental Protection Act requires at least the secondary treatment system for all publicly owned treatment works such as municipal wastewater treatment plant, so that effluent requirements of 30mg/L for BOD and 100mg/L of SS are achieved.


BASIC DESIGN CONSIDERATION ESSENTIAL CONSIDERATIONS

Significant factors that are essential for the design of wastewater treatment processes and plant units include the following:

a) Strength and characteristics of wastewaterb) Flow rates and their fluctuationsc) Mass loadingd) Design Criteriae) Hydraulic flow diagram


BASIC DESIGN CONSIDERATION cont…A) STRENGTH & CHARACTERISTICS OF

WASTEWATER

The strength of wastewater is normally expressed in terms of pollution load, which is determined from the concentrations of significant physical, chemical and biological content of wastewater.

B)FLOW RATE AND THEIR FLUCTUATIONS

Is the quantity or volume of wastewater in terms of rates.

Its is the total quantity of wastewater generated daily and to be treated every day.


BASIC DESIGN CONSIDERATION cont…C) MASS LOADING

Analysis of mass loading:

Involves the determination of the flow rate and mass loading variations

Involves determining the simple average or flow weighted average, concentration of specific constituents, mass loading (flow rate times concentration) or sustained mass loading

In almost all cases, a flow-weighted average should be used because it is a more accurate method of analysis.


BASIC DESIGN CONSIDERATION cont…Simple Average:

X=1/n(∑Xi)Where,X=arithmetic average conc of the constituentsn=number of observationXi=average concentration of the constituents during the “i” time

period (eg. i=5 if 5 sample for 5 different day)

Flow Weighted Average:

Xw=(∑xiqi)/∑qiWhere,Xw = flow –weighted average conc on the conctituentn=number of observationXi=average concentration of the constituent during the “i” time periodQi=average flow rate during “i” time period.


BASIC DESIGN CONSIDERATION cont…D) DESIGN CRITERIA

The data determined through the research and laboratory scale model studies as well as those obtained from the operational experience of field and pilot scale ww treatment facility. The values of such guideline parameters are called design criteria and available in the literature.


BASIC DESIGN CONSIDERATION cont…

D) DESIGN CRITERIA cont…

The most frequently assumed criteria for designing a conventional wastewater treatment plant (WWTP) are as follows:

• Detention period or time• Flow through velocity• Settling velocity• Surface loading rate @ over flow rate• Weir loading rate • Organic loading (BOD @ COD @ VSS loading)• Food to Microorganism ratio, F/M• Mean cell Residence Time• Hydraulic Loading• Volumetric Loading• Basin geometry (L:B:D) length, breadth and depth

ratio.


BASIC DESIGN CONSIDERATION cont…

E) HYDRAULIC FLOW DIAGRAM

Show the detail of wastewater levels as the average and peak flow are prepared.

As, it shows the reduced levels or elevations of wastewater surface and the top surfaces of all the units of a treatment plant, level of other significant features like weirs, tops and bottom of units, foundation levels of pump etc.


END FOR PART (A)

ert 417/4 waste treatment in bioprocess industry sem 1 (2010/2011) ‘physical treatment processes...

Documents

subsequent treatment

wastewater solids

bioprocess industrysem

large solids

physical treatment methods

solids buildup

grit removal processes

bar screen bar rackert