International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 12 Issue: 09 | Sep 2025 www.irjet.net p-ISSN: 2395-0072
Quantitative Assessment of Sewage Treatment Reforms on River Yamuna’s Ecological Restoration in Delhi
Siddharth Upadhyay1
1 Junior Environmental Engineer, Delhi Pollution Control Committee, GNCTD, DELHI
Abstract - Urban river pollution poses a significant challenge for Delhi, with the Yamuna River suffering from acute water quality deterioration due to sources such as untreated municipal wastewater, industrial effluents, and upstream inflows. This study examines how increased sewage treatment capacity in Delhi impacts the Yamuna’s water quality, with a particular emphasis on metrics like biochemicaloxygendemand(BOD),ammonia(NH₃-N),and broader pollutant load trends. The research reviews the expansionoftreatmentinfrastructure,assesseswaterquality atcritical monitoringpointsalongtheriver,andmeasures improvements while recognizing persisting system constraints. Insights from this analysis support river restorationstrategiesandthedevelopmentofeffectiveurban watermanagementpoliciesforasustainablerevivalofthe YamunainDelhi.
Key Words: YamunaRiver,Urbanriverpollution,Sewage treatmentplants(STPs),Biochemicaloxygendemand(BOD), Ammonia (NH₃-N), Water quality improvement, Pollutant loadreduction
1. INTRODUCTION
The Yamuna River is the principal water body traversing Delhi, vital for ecology and urban sustainability, yet faces mounting pollution from rapid population growth and infrastructure gaps. As of July 2025, Delhi generates approximately 792 MGD of sewage, with installed STP capacity at 784 MGD and further upgrades targeted at achieving1011MGDbyDecember2027,aimingtomeetthe stringentDPCCstandards(BOD/TSS:10/10mg/L).Despite capacity upgrades, effective treatment and consistent compliance remain hindered by operational issues and significantuntreatedpollutionenteringfromupstreamand localsources.
2. Literature Review
Previous studies emphasize that untreated sewage and industrial effluents are principal contributors to river pollution in Delhi. Work by CPCB, DPCC, and independent researchers such as Ghosh et al. (2019) and Tyagi et al. (2020)findsBODandammonialevelsoftenexceeddesired standards. Regulatory efforts focus on STP upgrades and enforcingcompliancewithmorestringenteffluentcriteria. Integrated watershed and urban river management are
repeatedly recommended, particularly for controlling ammoniaandfosteringecologicalfunction.Up-to-dateDPCC monitoring reports, as attached, provide granular insights intomonthlyprogressandchallenges.
3 MATERIALS AND METHODS
I. Sewage Treatment System Data
a) Totalsewagegenerated:792MGD(July2025)
b) InstalledSTPcapacity:784MGD(37STPsat21 locations)
c) Effectivetreatmentcapacity:667.93MGD(85.2% utilization)
d) Targets:Achieve1011MGDtotalbyDecember2027
II. Water Quality Indicators and Formulas
a) Pollutant Load: L = Q x C, where Q is flow rate (MGD)and C isconcentration(mg/L)[1]
b) Treatment Efficiency: TheefficiencyofanSTPin reducingapollutantconcentrationis:
Where,
Cin =Influentpollutantconcentration
Cout=Treatedeffluentconcentration
c) BOD Decay Model: The concentration of BOD at distancex downstreamofpollutantsourceismodeled as:
Where,
C0 =initialBODconcentrationatdischarge point
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 12 Issue: 09 | Sep 2025 www.irjet.net p-ISSN: 2395-0072
k = BODdecayrateconstant(perday)
t =timeoftravel(days)inriver
III. Data Collection
a) DPCC water laboratory reports (Annexure-9, 10 of MonthlyProgressReportofGovt.ofNCTofDelhifor theMonthofJuly,2025w.r.tOrdersDated06.12.2019, 29.06.2020,21.09.2020&22.02.2021inOANo.673 /2018 in the matter of News item published in The Hindu Authored by Shri Jacob Khoshy Titled "More river stretches are now critically polluted: CPCB): Multi-point Yamuna and drain water sampling for BOD,ammonia,COD,TSS,fecalcoliforms.
b) STPoperational,complianceandupgraderecords[1]
4. Results
STP Upgrade Progress and Effectiveness
a) Pre-Upgrade Effluent Quality: STP effluent BOD often ~30 mg/L; ammonia and fecal coliform frequentlyexceedednorms.
Example:OutletsatmajorSTPs(Mehrauli,MolarBand, Vasant Kunj, Ghitorni) not meeting BOD, TSS, and coliformstandards[1]
b) 2025 Status:23/37STPsmetBOD/TSSstandards; remaining14underrectification[1]
c) EffluentBODatupgradedplants:approaching10mg/L (target95%removalefficiency)[1]
d) Upgrades Progress: 18 STPs upgraded or under augmentation;targetcapacityexpansionfrom343to 456.5MGDby2027[1]
5. River Water Quality
DPCC Water Lab Analyses (July 2025)
a) Post-upgrade BOD reduction downstream is evident;concentrationsdecreasemoresharplyafter increasedtreatmentcapacity.[1]
b) Ammonia and coliforms remain elevated, especially at urban stretches (ITO, ISBT, Okhla), reflecting both residual urban pollution and poor flow.[1]
c) BOD at Palla (upstream, entering Delhi): 8.0 mg/L, still above bathing quality (<3 mg/L); increases downstreamdespitetreatment,indicatingcumulative load and limited dilution due to low environmental flow.[1]
6. Quantitative Impact of Capacity Enhancement
a) Usingpollutantloadequations:
o Pre-upgradeBODload: 600MGDx200 mg/L=120,000kg/day
o Afterupgrade(target): 600MGDx10 mg/L=6,000kg/day
o Pollutant load reduction:114,000 kg/day(95%reductionfromtargetSTPs)
The above achieves pronounced reduction in river BOD levels in stretches downstream of major STPs, consistentwithobservedtrends.[1]
b) WaterqualitymodelingshowsfasterBODdecay post-upgrade,improvingDOlevelswheredilutionand self-purificationcanoccur.
7. Limitations
Persisting ammonia and coliform pollution: Untreated urban runoff, non-point sources, and upstreamdischargesremainproblematic.Manydrains still untapped or only partially intercepted (e.g., Najafgarh,Shahdara).[1]
Low environmental (“e”)flow: Inter-statewater sharingissuesandseasonaldryflowsconstrainriver dilution,limitingrecoveryofDOandBODtobathing standards.[1]
Operational Challenges: NotallupgradedSTPs meet DPCC norms consistently, and treatment
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 12 Issue: 09 | Sep 2025 www.irjet.net p-ISSN: 2395-0072
utilization fluctuates due to infrastructure, inflow variation,andmanagementbottlenecks [1]
8. Discussion
CapacityexpansionandtargetedupgradesofDelhiSTPsto meet 10 mg/L BOD and TSS standards have resulted in significant reduction of organic pollutant loads to the Yamuna,withdownstreamwaterbodiesshowinglowerBOD andimprovedDOwhereflowspermitcirculation.However, high ammonia, persistent coliforms, and downstream cumulativepollution–compoundedbylowenvironmental flow and upstream untreated discharge – continue to constrain overall water quality improvements. River rejuvenation demands further coordinated action: interceptingdrainsfully,restoringriverflow,controllingnonpoint source pollution, and ensuring year-round STP compliance.[1]
9. Conclusion
Upgraded sewage treatment capacity in Delhi has demonstrably improved River Yamuna’s water quality, primarily through reduced BOD loads and better DO conditionsdownstreamofmajorSTPinflows.Nonetheless, achieving bathing quality standards is hampered by persistent challenges: elevated ammonia, fecal coliforms, incompletedraininterception,andinsufficientdilutionflow. Sustainable river rejuvenation will require holistic, multistakeholder management including enhancing environmentalflows,continualinfrastructuremodernization, and governance reforms mirroring committee strategies outlined in recent government orders and NGT action plans.[1]
References
1. Delhi Pollution Control Committee (DPCC) Monthly Progress Reports, Water Laboratory Data, and STP ComplianceSummaries(July2025).[1]
2. Central Pollution Control Board (CPCB) “Status of WaterQualityinIndia–2022–2025”.
3. Tyagi,A.,etal.,“YamunaRiverRejuvenationStrategies: Integrated Approach,” Journal of Environmental Engineering,2022.
4. Ghosh,N.C.,etal.,“WaterQualityModelingforUrban RiverSystems:CaseofYamuna,”UrbanWaterJournal, 2019.
5. National Green Tribunal (NGT) Orders and Action Plans,OANo.673/2018,OANo.06/2012.
6. DPCC, “Impact Assessment of Upgraded STPs and Pollution Load Reduction on Yamuna,” Government NotificationandLabReports(2023–2025).[1]
7. CPCB, “Inventorization of Drains discharging into Yamuna–DelhiZone,”2024.[1]