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“Analysis and Design of an Institutional Waste Water Management Scheme”

R.Ranjon Roy a

,T.R. Sreekrishnan b,B. J. Alappat

c

aM.Tech student, Department of Civil Engineering, IIT, Delhi 110016, India

bProfessor, Department for Biochemical Engineering & Biotechnology, IIT, Delhi 110016, India

cProfessor, Department of Civil Engineering, IIT, Delhi 110016, India

Abstract:

Environmental pollution has become a burning issue in today‟s world. Water is becoming a rare

commodity and many believe that future wars might take place for pure drinking water.

Recycling and recovering of wastewater becomes very important, especially in urban areas. Like

many educational / research institutions, IIT Delhi also generates both domestic and laboratory

wastewaters. Laboratory wastewaters contain different chemicals used in the various laboratories

of the Institute. Presently both kinds of wastewaters are getting mixed up and this mixed waste

water is going to the municipal sewerage system. With a view to treat and recover water from the

sewage, IIT Delhi is planning to separate these two waste waters and construct a STP for its

sewage and another ETP for its laboratory waste water. This paper describes the details of the

analysis carried out recently on the wastewaters and present a design for the STP based on

Sequencing Batch Reactor (SBR) concept.

Keywords: Sewage Treatment Plant (STP); Sequencing Batch Reactor (SBR); Pumping units

1. Introduction

In India, there are lots of research institutes and laboratories. In recent times, institutional waste

water has become a matter of concern because of its potential hazardous effect. A satisfactory

level of study to minimize this problem is yet to be reached because of various limitations. Many

institutes discard their waste water directly to the surroundings as they do not have proper

sewage treatment system.

The raw institutional wastewater contains various toxic organic and inorganic compounds,

chemicals, pathogenic microorganisms etc. If they are released into the environment without any

treatment, our natural water bodies will be severely affected by them. As we cannot deny the

contribution of educational institutes, industries and agricultural practices in our life, we must

find a solution to minimize the pollution. For this, the wastewater must be treated before

releasing into the environment. Sewage treatment is a process that removes unusual

contaminants from wastewater and brings back it to the environment for reuse. The treatment

includes physical, chemical, and biological processes to remove physical, chemical and

biological contaminants. Its objective is to produce a treated effluent and a solid waste (sludge)

which can be reused or discharged into the environment safely. However, the choice of

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appropriate and effective treatment system is very crucial. The sequencing batch reactor (SBR) is

one of the potential options for treating small and large-scale wastewater. SBR is a fill and draw

system for aerobic and anaerobic wastewater treatment. In this system, wastewater is added to a

single “batch” reactor where it get treated from undesirable components and then discharged to

the environment. Equalization, aeration, and clarification all can be achieved using a single batch

reactor.( Vigneswaran et al., 2007)

The SBR was first introduced by Arden and Lockett in 1914 which was based on active biomass

process (Arden and Lockett., 1914). Fifty years later, in 1970‟s research on SBR began rapidly

with the development of other discontinuous processes (Goroszy et al., 1970). From the current

study we can directly say that now SBR can be used with small and medium size waste water

treatment plants. Due consideration should be given to SBR not only for its economic reasons

but also for its treatment efficiency compared to other treatment processes at present. Apart from

usual advantages, another benefit of SBR that its can easily be adapted for continuous variations

of pollutant concentrations (Irvine and Ketchum., 1998). There are two principal design

conditions in SBR, one is how much supernatant is getting removed during the decanting

scenario and another one is the settle, decant and aeration time (Metcalf and Eddy., 2003).

(Lognathan et al., 2012) carried out study on a batch mode SBR to treat domestic wastewater and

the results showed that effective influent parameters were removed within 6 hr cycle time where

an aeration rate was 6 L/min. The goal of this study is to design a STP to solve the small scale

institutional waste water management problem.

2. Materials and Methods

2.1 Study area

Indian Institute of Technology Delhi is one of the eminent educational institutions in India. This

institute has a good number of laboratories in various departments, residential units, academic

blocks and a number of dormitories for its students. The campus has an area of 320 acres.

Currently, there are two sewer line networks which are being used to collect sewage from

campus using gravitational flow. The location of the STP is near to the Student activity canters

(SAC).Following map (Figure-1) has showed a new sewer line network to collect sewage from

both sump and deliver it to projected STP.

Figure 1: IIT Delhi map

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2.2 Work plan

The entire work plan is divided into four parts, i) analysis of the wastewater ii) designing of a

pumping station to deliver sewage to the projected STP iii) designing of the STP based on the

characteristics of the sample iv) designing a disposal unit. At present, two sewage sumps are

being used in IIT Delhi to collect the wastewater. One is Jwalamukhi sump which mainly

collects the residential wastewater and another one is Shanimandir sump which collects both

residential and lab wastewater. A horizontal pumping station has been designed to deliver the

sewage. The pumping station includes receiving chamber, coarse screen, and a pump. After

physicochemical characterization of the sewage, a STP was designed with SBR concepts. The

STP includes a receiving chamber, a medium screen, a grit chamber, two SBR basins and a

disinfection chamber. The process flow diagram of the project is placed below (Figure-2)

Figure 2: Process flow diagram of the project

3. Results and Discussion

This chapter deals with the design of the Sequencing Batch Reactor (SBR) at IIT D campus.

3.1 Characteristics of sewage

The waste water sample was collected from both the Jwalamukhi and Shanimondir sump and

pH, BOD, COD, TKN, ammonia nitrogen, TSS, coliform and total phosphorus were measured

according to the APHA (1998) standard method (Table 1). The measured parameters of the two

sampling site did not vary much. To design the STP, higher value of the measured parameters

were considered.

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Table 1. Characteristics of sewage sample.

3.2 Estimation of sewage generation

The current population of IIT, D has been calculated for the estimation of the total sewage

generation. The hostel resident data was collected from hostel‟s mess section and residential

population data was collected from Delhi voter electoral, 2015. Here, Malviya Nagar locality

numbers (48-53) was considered. These locality numbers only cover the IIT, D area voters and

forty-one percent of the residential population is below 18 years also considered (Census 2011).

Ultimate design period= 30 years

Approximately, present population in IIT, Delhi=12,500.

Assume, after 30 years population will be 16,000 (considering, 30% population will be increase)

The number of population will not increase drastically even after 30 years due to the limited

space of the campus.

Approximate number of Hostel Students = 8500,

Approximate number of residential population =7500

Hostel‟s water consumption = 135 lpcd (CPHEEO Third edition 1999, Manual on Water supply)

Residential water consumption = 172 lpcd (Source: Delhi Jal Board)

Parameter Jwalamukhi

Sewage Sump

Shanimandir

Sewage sump

Expected

Effluent

Design

Value

pH 7.48 7.51 5.5 - 9.0

7.5

BOD, mg/l

177.38 164.21 ≤10

180

COD, mg/l

270 264.43 ≤ 250

270

TKN, mg/l

45.8 45.1 ≤ 5

50

Ammonia nitrogen, mg/l

18.872 19.15 ≤ 50

20

Total suspended solid,

mg/l

790 580 200

790

Coliform, mpn/100ml 1.3 1.3 ≤ 1000

1.3

Total phosphorus, mg/l 7.2 5.5 ≤ 5

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Oil and Grease, mg/l 5.9 6.2 ≤5 6.2

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Assume, Sewage generation per day = 80% of supplied water

Total sewage generation from hostels = 8500 × 135 × 0.8 = 9,18000 l/d

Total sewage generation from Residents house =7500 ×172 × 0.8 = 10,32000 l/d

Total amount of sewage genreation = 19,50000 = 1.95 MLD ≈ 2 MLD = 83.33 /hr

Assume a peak factor=3 Hence, Design flow capacity (maximum)= 250 /hr =0.069 /s

3.3 Design of pumping units

A new sewer line network has been illustrated to deliver sewage in projected STP from both the

sumps. The overall pumping design was estimated 1.3MLD and 0.7 MLD for sewage generation

from the shanimandir and jwalamukhi area respectively.

3.3.1 Design of receiving chamber and coarse screen for pumping units

First of all, a rectangular-shaped receiving chamber (Table 2) is designed to collect the sewage

and control its flow. After that sewage is allowed to pass through a coarse screen. A screen is

used to trap the floating matters such as sachets, plastic milk packets, grocery bags etc., which

could disturb the impeller.

Table 2. Detailed design of coarse screen for both Shanimandir and Jwalamukhi sumps.

Design parameter Design Value

(Shanimandir)

Design Value

(Jwalamukhi)

Design flow, /s 0.045 0.024

Size of the receiving chamber, m 2 × 4 × 3 2 × 4 × 2

Number of screen 1 1

Clear opening area for screen, 0.15 0.03

Clear opening between bars, m 0.03 0.03

No. of clear opening, m 3 2

Width of channel for screen, m 0.7 0.6

Depth of channel for screen, m 0.5 0.4

Head loss through screen, m 0.00147 0.0013

Head loss on 50% clogging, m 0.00371 0.0035

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3.3.2 Designing of pumping system

The pumping station location should select such a way that, it can capable of adequating drained

the entire area. Here, Pumping station (Table 3) with horizontal pumps installed in the dry well

(Figure 3) was considered. The length of the new sewer line networks was calculated through

Google Map. The pumping system was designed according to „NPTEL wastewater management

web courses‟ by Dr. M.M. Ghangrekar.

Table 3. Detailed design of pumping system.

Figure 3. Horizontal pumps installed in the dry well (Shanimandir sumps)

Design Parameter Design Value

(Shanimandir)

Design Value

(jwalamukhi)

Design flow, 0.045 0.024

Diameter of rising tube, m 0.3 0.2

Wet well depth, m 6 5

Wet well diameter, m 3 3

Length of sewer pipe, m 1800 800

HP of motor required for highest

capacity pump, HP

19 , Provide minimum(3+1

stand by) pumps

10, Provide minimum

(2+1 stand by) pumps

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3.4 Designing of the Sewage treatment plant

3.4.1 Designing of a receiving chamber and a medium screen for STP

A receiving chamber (Table 4) was designed to control flow and seasonal variation of the SBR

tank. The receiving chamber has been designed such way that no biological activity can happen

in it. Apart from receiving chamber, a medium screen has also been included to remove floating

material. Here, a manual medium size bar screen (Figure 4a) has clear openings of 12 mm

considered. A weir has been used above of the screen to control the overflow.

Table 4. Detailed design of Receiving Chamber and Medium Screen for STP

Design parameter Design Value

Design flow, /s 0.069

Size of the receiving chamber, m 2 × 4 × 3 (0.5m for freeboard)

Number of screen in STP 2 (1 is for stand by)

No. of clear opening 3

Width of channel for medium screen, m 0.7

Depth of channel for medium screen, m 0.6

Head loss through screen in normal condition, m 0.0015

Head loss on 50% clogging, m 0.0064

3.4.2 Designing of a Grit Chamber

If inorganic particle will enter in the SBR basin it will affect the treatment process.Moreover it

also prevents damage to the pumps. Here an aerated grit chamber (Figure 4b) has designed. The

design procedure is shown below (Table 5).

Table 5. Detailed design of Grit Chamber for STP.

Design parameter Design Value

Design flow, /s 0.069

Width of Grit chamber, m 3

Depth of Grit chamber, m 2

Assume, Kinematic Viscosity of Effluent, /s 0.0000011

Assume, Particle Diameter, m 0.000150

Settling Velocity Settling Velocity, m/s 0.02

Removal efficiency , cum/sqm/d 1352.07

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Figure 4 (a). Section view of medium screen ;(b) Grit chamber for STP

3.5 Designing of Sequencing Batch Reactor (SBR)

3.5.1 SBR operating cycle Time

The design procedure of SBR is adopted according to the mass balance. As SBR process depends

more on time rather on space. So, operating cycle time is crucial part in the SBR process.

However, as SBR is a batch reactor, so to achieve a desired amount of treatment, an operator can

shorten or lengthen the operation cycle time. (Table 6)

Table 6. Detailed design of SBR operating cycle time.

SBR Steps Description Design

Time

Static Fill The raw wastewater enters in the SBR tank where no mixing or

aeration is performed.

0.75 hr.

Aerated Fill Both aeration and mechanical mixing are activated in this step.

The aerated filling time will start when the maximum filling time is

completed or top water level is reaches upto the mark.

1.5 hr.

React No additional influent wastewater is added in this step and both

aeration and mixing units are on. Nitrification is also resumed in this

step. In addition to this, the maximum organic matter is also get

reduced in this step.

2 hr.

Settle Aeration is stopped in this phase, that will allow to maintain a static

condition, which will promote settling of the biological flocs.

1 hr.

Decant This step extracts the treated effluent from the SBR basin. When

treated supernatant reaches the bottom water level in the SBR, the

decantation step comes to an end.

0.75 hr.

Idle Waste activated sludge can be extracted in order to attain rapid

settling (if require)

0.00 hr.

Total Total operation cycle time to run one SBR cycle. 6 hr.

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3.5.2 Dimensions and operating parameters of SBR

Here, two SBR basins (Figure 5) were considered for controlling and maintaining high flows and

seasonal variations. If one basin is obsolete then another basin would continue the process. Apart

from that, if activated sludge is depleted in one basin, then another basin‟s biomass would be

transferred to fix this issue (Ronald F. Poltak et al., 2005). SBR operating parameters and

disinfection chamber (Table 6) were also designed, where MLSS 3500 mg/l and F/M 0.12 were

assumed. Sludge retention time (SRT), Hydraulic retention time (HRT) and sludge production

are main operating parameter.

Table 6. Detailed design of SBR dimensions and operating parameters.

Figure 5: Sequencing Batch Reactor (SBR)

Design Parameter Design value

Flow conditions Peak flow

Number of basins 2

Volume of each basin, 450

Length, m 12

Width, m 7

Bottom Water Level, m 2.75

Maximum Water Level, m 5.5

Depth of the SBR, m

Dimension of disinfection chamber, m

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4 × 8 × 5

Number of cycles per day per reactor 4

Hydraulic Retention Time, hr 12

Sludge Retention Time, d 16

Sludge Production, kg dry solids/d 136

Total daily sludge volume wasted, /d 11.3

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3.5.3 SBR aeration requirements

The aeration requirements is the most crucial parameter for SBR design. Maximum cost of the

SBR depends on aeration requirements. The BOD removal and nitrification of TKN were being

used to calculate the total aeration requirements (Table 7). Here, the tubular diffuser was used for

its high efficiency and assumed to be 1m in length. The maximum diffuser elevation 200 mm

above the bottom of the basin is assumed. Furthermore, the number of the diffusers in the basin

were calculated from 10 scfm/ diffuser.

Table 7 SBR aeration requirements

4. Conclusions

The institutional wastewater management problem is the new-born issue. This paper is aimed to

solve wastewater management problem in the educational institute like IIT Delhi. However, the

hazardous waste water coming from laboratory was not considered here. We choose SBR in our

project because it requires less area than other treatment processes and it can be also adopted for

various concentration of waste water. The treated water will be supplied for the gardening and

horticulture in IIT, Delhi campus which will reduce the demands of fresh water. Moreover, the

treated sludge can be use in increasing soil fertility.

References

Ardern,E., Locker,W.T., 1914. Experiments on the oxidation of sewage without the aid of filters. J, SOC.

Chem. Lnd., 33, 10.

APHA., 1998.Standard Methods for the Examination of Water and Wastewater, 20th edition. American

Public Health Association, Washington, D.C.

Design parameter Design Value

Aeration time per day each SBR, hr 14

Oxygen for BOD removal, kg O2/kg BOD5 448.8

Oxygen for N Removal, kg O2/kg N 233.96

Actual Oxygen required (AOR) for BOD5, kg O2/d 751.036

Design Water Temperature, °C 30

Total daily SOR, kg O2/d 1779.02

AOR/SOR 0.4

Quantity of air required per basin, scfm 300.3

Design air flow per diffuser, scfm/unit 10

Number of tubular diffusers per SBR 30

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Dr.M.M. Ghangrekar.,NPTEL wastewater management web courses, Retrieved

fromhttp://nptel.ac.in/syllabus/105105048.

Goronszy, M. S., 1979. Intermittent Operation of the Extended Aeration Process for Small Systems. J.

Water Pollution. Control Fed.51, 274.

Irvine, R. L., Ketchum, L. H., 1998. Sequencing Batch Reactors for Biological Wastewater Treatment.

Crit. Rev. Environ.18, 255.

Locker,W. T., 1954. The evolution of the activated-sludge process. In: Proc. Annual Conf.: The evolution

and the Activated Sludge Process of Sewage Purification in Great Britain.lnst.of Sew.Purif, Blackpool.19.

Metcalf and Eddy., 2003. Waste Water Engineering Treatment and Reuse, 4th edition, Tata McGraw Hill

Publishers.

Ronald F. Poltak .,2005.Sequencing Batch Reactor Design and Operational Considerations, New England

Interstate Water Pollution Control Commission.

R. Lognathan., 2012.Biological Treatment of Domestic Wastewater Using Sequential Batch

Reactor(SBR).Indian Journal of Environmental Protection, vol. 32, No. 7.

Vigneswaran, S., Sundaravadivel, M., and Chaudhary, D. S., 2007. Sequencing Batch reactor: principles,

design/operation, case study, Encyclopedia of life sciences eolss.