India - Bombay Sewage Disposal Project : environmental assessment (Vol. 3 of 4) : Executive summary : aerated lagoons : Bhandup & Ghatkopar

, "iMnvirorim- mental j Assessme-n t/A>.h3a /inalysis r,,,,M3 Reports Report E0071 '1; Indi - ~~ ~ ~ i, 3of 4 Envirlonmeintal Assessment January' 1995 | ~ ~~~~~~~~ 34 of 4* This report has been prepared by the Borrower or its Consultant19 4~~~~~~ 44 .4 . .. M; i 0 , . X' D W SC 1" "'" S' t ,/,A k,,e4aS I^,, f , , .,., f  E X E C U T I V E S U M M A R Y BOMBAY SEWAGE DISPOSAL PROJECT AERAYED IHGOONS BHANDUP & GHATKOPAR SPONSOR MUNICIPAL CORPORATION OF GREATER BOMBAY NATIONAL ENVIRONMENTAL ENGINEERING RESEARCH INSTTUTE  BOMBAY SEWAGE DISPOSAL PROJECT CONTENTS LISTOFTABLES LISTOF FIGURES PREAMBLE 1 BOMBAY SEWAGE DISPOSAL PROIECr 1 THE PROPOSED 14ACILTIES - 1 NEED FORPRESENTSTUDY 2 OBJECTIVES OF ENVIRONMENTAL ASSESSMENT 2 ENVIRONMENTAL STANQARDS 3 METHODOLOGY FOR ENVIRONMENTAL ASSESSMENT 4 EXISTING ENVIRONMENTALSTATUS 4 ENVIRONMENTAL IMPACIS OF PROPOSED PROJECT 5 ANALYSIS OF ALTERNATIVES 6 MITIGATION PLAN II RECOMMENDATlONS ENVIRONMENTAL MONITORING 1 () PUBUC RTRI1CIPATION 11) INSTITUTIONAL NEEDS II APPENDiX I -TABLES 12-17 APPENDIX 11-FIGURES 1 -2U 1tif)WVY SEVC I DISP'OSA lAlRI 3F(T BUANDUP & GNROPAR LAGOONS  BOMBAY SEWAGE DSPOSK PROJECT UST OF TABLES Table 1 Sizes and Specifications of Aerated Lagoons Table2 Present and Projected BOD Loads in Thane Creek (Municipal Discharges). Table 3 Water Quality Distribution in Thane Creek for %hrious Management Scenarios. Table 4 Mitigation Plan for Construction and Operation Phase Impacts of Aerated Lagoons. ULST OF FIGURES Figure I Service Areas and Wastewater Treatment / Disposal Schemes Figure 2 Schematic Layout of Treatment Units -Bhandup. Figure 3 Schematic Layout of Treatment Units -Ghatkopar- BOMIAY SEAWUE DPAL PRCOIELT BWHUF & UIOPAM LMONS  BOMDAY SEWAGE PREAMBLE DISPOSAL PROUJECT 1. Bombay is the hub of comnercial and industrial activilies andc has witnessed a rapid growth during past few decades. Executve Summary According to 1991 census, 9.93 million persons reside within the municipal limits of Greater Bombay which has a land area of 603 square kilomete 2. The infrastructural development, however, has not kept pace with the growth of population. As a result, the city suffers from shortage of all basic amenities including housing, water supply, sanitation and transport. Amongst these, sanitation is perhaps the most neglected sector. Only a miniscule proportion, 22.5 mid out of approxcimately 2000 mid municipal wastewater generated in the city, receives treatment before disposal to adjoining coastal and creek regions Discharge of such large quantity of untreated sewage intt the marine envirnniwillnt hias resulted in widespread impairment of coastal and creek water quality. BOMBAY SEWAGE DISPOSAL PROJECI (BSOP) 3. The first integrated wastewater management scheme for the city was planned in 1970. The scheme envisaged disposal of screened wastewater from entire Bombay miunicipal area through two marine outfalls at Worli and Bandra. 4. The plan, since then, has undergone many revisions. The mxst recent Development Plan III, divides the Bombay municipal region into seven service areas. The plan prvides foir disposal of wastewater after preliminary treatment thrmugh marine outtalls at Colaba, WMrli and Bandra intol coastal sea and afler treatment in aerated lagoons at Bhandup and Ghatkmpar in Tilne creek and at Malad and Wvsova in Malad creek. respeclively (rigure 1). THE PROPOSED FACILITIES Aerated lagoons 5. The proposed lagoons, are conbinatioin tf aerohic ant facultative lagoons. Each lagoon comprises of frur identical streams of three cells of average residence tinie of 1.4, 1.h and 1.1 days, respectively. Out of three cells, the first cell is designed to operate as a flow-through aerated lagocm and the folloving two cells as facultative aerated lagoons. The (ver-all remv(al efficiency of the treatbent system is expected t l he 80 per cent for Biochemical Oxyglen Demand (BOD) and 70 pxr cult for Suspenided Solids (SS). 1 lie salient design details of ii te aerated lagooxns are presenled in Table 1. RiaYlW 5sEVGE 1I5I')SAL PWKOECr IIANUP & UAUUFPAU IAUDNS I  X EXC UT I V E 6. Due to financial constraints the original plan nf implenaentation SUM M A RY has been modified and implementation has heen divided into two phases. During the first phase activities, the rilst cells of four. streams are being constructed and will be operated as facultative aerated lagoons with e cpected BOD removal efficiency of 50 per cent. Figures 2 and 3 describe the layouts cf the aerated lagoons at Bhandup and Ghatkopar, respectively. The shaded portion in these figures indicate the facilities proposed to be built during the first phase. NEED FOR PRESENT STlDY 7. The present study has been undertaken in keeping with the World Bank policy and procedure for the environmental assessment of bank lending operations with respect to Bombay Sewage Disposal Project, Development Plan Ill. Procedures as listed under OperatEonal Directive 4.01 have been followed during the assessment. The study also meets the requirements of the State of Maharashtra and the Government of India for environmental clearance of development projects. OBJECiIVES OF ENVIRONMENiAL ASSESSMENT 8. The objective of this environmental assessment study hias been to evaluate the impact of proposed first phase facilities at Ohandup and Ghatkopar on the water quality in Tlhane creek. The study also envisaged to ascertain whether the facilities when augmented to three cell lagoons would he adequate to provide the desired water quality benefits and if not, what modifications in the form of higher degree of treatment and mode of disposal would be necessary. The design period for the primary recommendations has been kept upir 1he year 2005. 9. in view of the need to detine water quality management framework beyond the year 2i)l; Ihe utudy wa% al) expected to evaluate wastewater trealmeol noplity. in' twie year 2015 and after. The objective fur .ucti exien'."n w.". iiixw.ivde hbrad guidelines for future wastewater manageement ii ihe creek. As the project involves large scale constructiconi activities. Ithe %ludy. also aimed at assessing the potential negative impaces dUrin%g. the construction phase of the project and delineation ri necessary mitigatory measures. 10. With the above objectives, the study was planined to ccwer the following environmental aspects: * Assessment of environmental impacts of protxised aerated lagoonls on waler qtuality in Thane creek witli special emphiasis on improvniienit of DissoilvedL Oxygel (DO) ILmels. RtMlf 4SEIWUE D)ISPOSAL PROJCr BAUNUP & UHATCPAJIR LC1NSz  U X E C I T I V E * Evaluate the existing water quality in Tlane creek and the S 11 J AI Y adequacy of proposed single and three cell aeratel lagoo)ns at Bhandup and Glhatkopar to achieve lhe acceptahle DO levels of the creek wate. * Field investigations and data collectioni to set up appr priate hydrodynamic and solute transport model for Thane creek to enable water quality predictions. * Based on the modeling studies, broadly delineate possible augmentations of proposed scheme with respect to additional wastewater zreatment/ transport/disposal measures for planning beyond the year 2005. * Assessment of impacts on air, noise, land, water and sodi-economic environment due to construction of aerated lagoons and delineation of mitigatory measures. ENVIRONMENTAL STANDARDS 11. Environment (Protection) Act, 1986 vests in Central Governmert, the powers to lay down standards for environment protection. Central and State Pollution Control Boards are responsible for compliance of these standards. The Boards, based on local conditions, have power to stipulate more stringent location specific standards. 12. For protection of coastal water quality, two standards apply in India. The first of these standards is in the form of receiving water quality and is based on best designated use of the water body such as for bathing, fishing or navigation. The creek and coastal waters used for recreational purposes or fisliing, accordingly. should always have BOD less than 5.0 mg( L, total coliformis nut more than 1000/1 00 ml and DO ilonre than .4.0 Ing L 13. The second is in the form of effluent standards kir discharges into marine coastal area. According to this standard. effluents with BOD and SS up to 100 mg/ L each and ammnwniacal nitrogen up to 50 mg/L can be discharged into the crefeks. 14. The standards for receiving water and effilent discharges di) not complement each other as the latter does not take into account the assimilative capacity of the receivir.g waters. If the effluent volume is large, discharges in compliance with the effluent standard may still lead to severe deterioratioFn of receiving water quality. Also, for smaller water bxodies, even-a very high degree of treatment of municipal discharges may fail t) comnply witll hacterial quality prescribed lby thie receivinig water standard. A rational view, thus, would be to t ake decisiomns whici eisIIre DO ROMPAY 5EWE DISPOML MOJC B*MUP & GIAM PAR LAID0NS  E X E C UTI V E levels necessary to achieve minimal conditions tn sustain a S U Ml ALI A ) healthy creek ecosystem in the receiving watem. The water quality management objective for Thane creek was, therefore, aimed at achieving a minimum DO level of 2 rig/ L. MErHODOLOGY FOR ENVIRONMENTAL ASSESSMENT 15. In order to assess adequacy of proposed treatinent fcilities at Bhandup and Ghatkopar, the existing water quality status of Thane creek was determined through elaborate field surveys. As inputs to water quality model, hydrodynamic and bathymetric data on Thane creek were also collected. 16. Water quality predictions were carried out niainly for DO and BOD, using mathematical models. These models were calibrated for local environmental conditions through in-situ and laboratory experiments. 17. For processes involving highly complex interactions such as nutrient enrichment, bioaccumulation and ecological transiormadons, the approach of observations at and inference from the regions which have beeni receiving similar wastewater discharges wer a long period was adopted. 18. For estimation of constructicn pliase impacts, field investigations on ambient air quality, noise levels, creek and coastal water quality were conducted. Land-use pattern and soil characteristics near the construction sites were also studied. Area under mangrove cover in entire inner Thane creek was determined through satellite imageries. 19. The observations and mrodel predictions were used tto examine the efficacy of proposed single and three cell aerated lagot wn' in achieving the desired envirnnmental benefis, Probhable augmentations cof the pmposed treatinet-f etin cait-ring t] inlcrea'sed flos b tle ye.r 20? 5 altld Mtl.S in} ilut- kirni of higher treatment and options for wa%tewater cir.aI % at ntw lutrcaitin in the creek, were evaluated. The scopje fior adiditiminal field - hservations and modeling work tn finalise such optirtir. was also Iigliighlited. EXISTING ENVIRONMENTAL SUATUS 20. The miajor inpacts of preI_seilt wastewater discharges are creek water quality impairment in terms of loyw DO, hiigh BOD, SS and total colik)nnms Thane creek, in its inier regions, receives appipximately 400 mild untreated wastewater frtmi Bliandup and Gliatkopiar service areas. Due it) shiallow tdeptlis and tlamvw crtss%-seclion1, tlhe creek ii Ilbis rwgio:ti ch's o! h;vm sutificient IHOMIAY 5VEAI;E tISI'0'AL P'ROIE(.T BIIANDOP & EHT0KPAR LAGOINS 4  E X E C I T I V E capacity to assimilate these discharges As a result, almut 10 S U M 1M A I T kilometers long stretch along the west hank of the creek exhibits poor water quality characterised by low DO and lhigh BOD levels. 21. Concentrations of BOD as high as 7 mg/L and total coliforms exceeding 10I1tOO ml are frequently observed in the creek. Observations on biological indicators present a picture similar to those of physico-chemical parameters. The creek sediments also show high concentration of nitrogen, depicting accumulation of nutrients due to large wastewater discharges. 22. Ambient air quality analyses at Bhandup and Ghatkopar aerated lagoon sites indicate that present air quality in temis of NO, and S02 at both sites fall within Indian standards for ambient air quality. 23. Observations on noise levels at the lagoon sites are within the limits prescribed for urban residential areas. ENVIRONMENTAL IMPACtS OF PROPOSED PROJECr Construction phase impacts 24. The major construction activities for the project are site clearance, land filling, earth work and miaterial transfer. The most important impact of these activities is the loss of about 40 hectares of mangrove cover amounting to 5 per cent of total mangrove forests in inner Thane creek. Quantitative estimation of impact of such reclamation on Thane creek water quality is not possible. However, considering the role nf mangroves in sustenance of coastal ecosystemn. it is essential tn compensate for the lost mangrove cwver. 25. The other prominent impacts during thie r in mirthIOR are rise in ambient noise levels and marg:inal increwae in air bornne pollutants like SPM at the ctinorucimn %nit. The higher 5PM levels would he witnessed Iwr 'Jiti rt ptri. 4 aiilv dUring peak perinods *f cors-truction acKtivities. Tlhere will lk- m%igimticlant increase in thle gaseous pollutants such a SO. ancl NO,. 26. Predictifgs of nzoise lievIs at flhe 5cInsitiVi lt)ralIIr. Iimc-;ut'd -it *iire tlhat 1 kilmnieter distance fri: IIi w aerared lagtmans. indicate an addition of 40 dBA to a simlilar background noise level at the time of construction activities. The noise due tv constructions, thus, will he attenuated to the 13ackground levels at sensitive locationis. 27. With the exception of lhe effects of mangrove loss (see para 24.), construction of aeraled lagoons will nlolt have any adverse imiipacts oni creek waler quality or fisliinUg itIerel9C aS all IIOMIIAY SEVWC E 1)151'0SL IRt)OIECT BAIIUUP & GRAKOPAR lAUtONS  EXECUTIVE construction activities eccept for effluent channel will be S U MM A I T restricted to land. The construction is ntt expected to have significant impacts on drainage diaracteristics (if the region. However, it will be necessa,y not to block any natural drainage channel In the vidnity of lagoons. Operational Phase Impacts 28. The planned treatment level at Bhandup and Ghatkopar aerated lagoons along with the present and projected flows for the year 2005 are presented in Table 2. Thane creek water quality projections developed through rigorous hydrodynamic and water quality modelling, indicate that the proposed first phase treatment effort through single cell aerated lagoons would not provide significant improvement in creek water quality. Such implementation would, however, arrest rising trend of water quality impairment. 29. The present design capacity of Bhandup lagoons is only 1 80 mid against the estimated floNs of 280 mid. If built to the design flows, Bhandup lagoons will he considerahly over loaded. It will, therefore, be necessary to redesign the Bhandup lagoons for the new flows. 30. H2S emission in the event of malfunctioning of the aerators could lead to significant odour nuisance within 1 kilometer radius of the lagoons on a typical stable winter day. However, impacts would not be significant in areas whichi are beyond 1.5 to 2 kilometers distance from the lagoons. ANALYIS OF AITERNAIlVES No action scenario 31. The municipal wastewater discharges froti Blhandup and Ghatkupar service areas are presently estimated at 40() mid and are expected to rise to 515 mid by the year 2005. A further steep rise in wastewater generation in these service areas is expected due to planned augmentation of water supply. By 2015, wastewater generation in these areas is expected to) reach 1( W mid. If no wastewater treatlnent facilities are impvlem1ented. creek water quality which already exhihits widespread impairment during the low tides, would be considerably further degraded. Augmentation of wastewater management effort 32. When augmented t) three cell aerated lagooins designed to achieve 35 iig/L or lower BOD in the effluents, ilhe proposed wastewater Ireatnlelt would Ironvide adequaite level of Ix)llution NOMAY SEVAGE DISPOSAL PROIECT IUNUaP & ImnmOrPn Ag6ONS  E X E C U V T I E abatenent in the affected creek region untill wastewater flows I U 1 M11 I Y exceed the projected flonws for the year 2005. 33. Water quality scenarios developed to examine the benefits of further raising the treatmnet level at Ghatkopar k) activated sludge process indicate that such augmentation for 2005 flows would give rise to only a marginal improvement of 0.3 mg/ L in creek dissolved oxygen over three cell aerated lagoons option. Shifting effluent discharge location t) center of the creek also does not yield any significant improvement in creek DO. Long term water quafity perspective 34. When extended to 201 5 flows, the simulations indicated that it was not feasible to discharge effluents beyond projected flows for the year 2005 at Bhandup and Ghatkopar even after nitrification of effluents. For future flows, it will be necessary to build additional wastewater treatment acilities and discharge the effluents at new locations in the creek. The analysis indicates, that, if one were to discharge within the inner Thane creek, it would be possible to discharge upto 260 mid after secondary treatment near Vikhroli. To cater to entire excess flows of 520 mid between the year 2015 and the year 2005, however, such option would entail tertiary level treatnent The simulated creek -dissolved cxygen levels for management scenarios described above are summarised in Table 3. 35. Considering the high cost of tertiary treatment and also tlie need to plan even beyond the year 2015, it is desirahle that options for discharging the wastewaters in otler regions of the creek Ne explored. Under such case, it may be adequate to treat the effluents only upto secondary level anrI cost of transporting the wastewater may be off-set by savinprs in the cost 'f its trealitieril. Socio-economic impacts 36. The project area for Bhandup arid Ghatkopar lagxotns is uninhabited and does not involve any displacement oti peojple. The project, during the conistructioni, is expected to generate some employment which would have marginal positive impact. The operation of aerated lagoons dues not require a large workforce and, therefore, no large scale residential development in the region is expected, due to implementaticrn uf the project. The implementation of the project, may result in 1eneficial inpacts in terms of higher filh yield thereby increasing fishing activities in inner Thane creek. BOMBAY SEWU'.E DISPOSAL PROjECr 8WiI19DS UTVA.' DP I .11.n . .R IAUUNB 7  EXECuTIVE MITIGATION PLAN SUlIMMAIY Construction phase 37. Loss of ahout 5 percent of the total mangrove cover in ithe inner Thane creek due to land reclamation for lagoons, is the most important construction phase Impact of die prolect. To conipensate for the unavidahle loss of mangrove area, MCGB should designate about 200 hectares of mangrove area alongl the creek as protected area and take measures against further reclamation or unauthorized cutting. Alternatively, MCGB should undertake fresh planting of mangrove forests (f area equivalent to the reclaimed area in ihe inner Thanie creek region. 38. Another potentially negative impact of aerated lagoon construction is a rise in the anibient noise and dust levels. This impact can be prevented by adherence t) good construction and house keeping practices. Measures such as avoidance of unnecessary idling of construction machinery and spillage of fuel and oil and adequate mainitenance (of construicti(on machinery to ensure efficient and troulale free operation shloZuld be provided for in the construction contracts. 39. Analysis of the noise levels at the site andt %turriiundillg areas indicate that the effect of coisirtciciia aclivItIt' (Lurinfg thle day, is not felt outside the construction site dur tIn the lical nnises. At night, however. the construction activilies can raise 1he noise levels and the nearby residential locations beyond the nlig;ht ti.me standards for such areas. The noise generating construction activities, therefore, should be restricted oinly tit day lime hIturs. 40. Air quality analysis at the sites indicates tlit- air clualatb ll tflern% of SPM, NO2 and 5