Sewerage, Sanitation, Drainage & Rainwater Harvesting – Exam Notes & Flashcards

Sewerage, Sanitation, Drainage & Rainwater Harvesting – High-Yield Exam Notes

Compiled from URDPFI Guidelines (2014), CPHEEO Manuals (Sewerage & Sewage Treatment 2013; Water Supply), MoUD Guidelines (DWWM 2012; Septage 2013), Environment (Protection) Rules 1986, NDMA Urban Flood Management (2010), CGWB Manuals. For architecture & planning exam revision.

Exam-ready Units: sqm/ha/lpcd/mg/L/µg/L/Bq/L

Topic-wise Wrapped Notes

National Urban Sanitation Policy (NUSP, 2008) – Aims & Basics

Transform urban India into community-driven, totally sanitized, healthy, liveable cities; manage sewage and stormwater safely; ensure services to the poor; improve public health and environmental standards.

Cities must be open defecation free; eliminate manual scavenging with PPE for worker safety.
Municipal sewage & stormwater to be safely managed; promote recycle/reuse for non-potable uses.
Solid waste to be collected and disposed safely; systems to sustain results.
Objective: collect → transport → treat → dispose without health/environmental harm.

Wastewater Quantity for Design (CPHEEO)

About 80% of water supply reaches sewers; however, design with a minimum wastewater flow of 100 lpcd is recommended.

Use 100 lpcd as minimum design flow for sewerage systems.
Adopt prospective population horizons as per component design periods.
Plan for phased STP construction when initial flows are low.

Decentralised Wastewater Management (DWWM)

Collection, treatment, and disposal/reuse near the point of generation (homes, clusters, institutions, portions of cities); utilizes both liquid and solid fractions locally.

Design period: ~15 years (or current capacity + 20% provision).
Refer siting, components, wastewater characteristics in CPHEEO Draft Manual (2013).
Consider local land availability, technology, O&M capacity.

Centralized vs Decentralized Systems – Selection

CWMS offers comprehensive collection/transport but has high capital and O&M; DWMS reduces load on central STPs and suits distributed reuse. Choose based on growth, reuse options/quality, technology, management structures, and issues to enable reuse.

Reuse of urban sewage for non-potable uses reduces potable demand.
Technology choice depends on sewage composition, land, funds, expertise.
Plan O&M sustainability using local resources and manpower.

Effluent Standards (MoEF/EP Rules, 1986 – General)

Key limits for discharge to inland surface water, public sewers, land irrigation, and marine/coastal areas.

pH 5.5–9.0 across categories; discharge temperature ≤ 5°C above receiving water.
BOD (3 days @27°C): 30 (inland), 350 (sewers), 100 (land/marine).
COD: 250 (inland, marine).
Oil & Grease: 10 (inland/land), 20 (sewers/marine).
Heavy metals: e.g., Pb 0.1 (inland), 1.0 (sewers), 2.0 (marine).

Recommended Treated Sewage Quality at Point of Use

Quality varies by end-use (toilet flushing, fire protection, vehicle wash, non-contact impoundments, landscaping/horticulture/agriculture).

BOD target: generally 10 mg/L (most uses), 20 mg/L for cooked crops & non-edible crops.
Residual chlorine: typically 1 mg/L (0.5 for non-contact impoundments; none for some recreation to protect biota).
Turbidity: < 2 NTU; Faecal coliform: Nil for most; ≤ 230/100 mL for certain agriculture.

Recycling Technologies – Salient Features

Common STP process options and indicative land, capital and O&M ranges per MLD.

ASP: 0.15–0.25 ha/MLD; ₹2–4 cr/MLD; O&M ₹0.3–0.5 m/yr/MLD.
WSPS: 0.8–2.3 ha/MLD; ₹1.5–4.5 cr; O&M low (₹0.06–0.1 m/yr/MLD).
FAB: ~0.06 ha/MLD; ₹3–5 cr; O&M ₹0.6–0.75 m/yr/MLD.
SAFF: ~0.05 ha/MLD; ~₹7 cr; O&M ~₹1.14 m/yr/MLD.
Other options: UASB, DPS, FAL, TF, BIOFOR, CASP (see table for specifics).

Septage Management – Planning & Implementation

ULBs require baseline data (onsite systems, desludging history), zoning, pilot schedules, and feasible disposal/treatment arrangements within ~20–30 km.

Select treatment option by town size, land, proximity to STP, and techno-economic feasibility.
Steps include: data collection, service inventory, land identification, draft regulations, technology choice/design (STDF), procurement, awareness, training, and phased service rollout.
Management can be municipal or via private contracts; user fees recover O&M.

Public Toilets – Norms in Public Areas

Provision on roads and open areas at ~every 1 km, including parks, plazas, OATs, pools, car parks, fuel stations; disabled-friendly; 50–50 M/F.

Signage with directions & distance; helpline displayed.
Modes: pay-and-use or free; typical use window 15–20 minutes.
Cleaning: attendants for both genders or auto-clean cycle (~40 s); open 24×7.

Drainage – Separate from Sanitary Sewers

Sanitary sewers should not receive stormwater; design a separate system for storm runoff.

Runoff depends on geology, topography, rainfall intensity/duration, and land use.
Two common estimation methods: Rational Method and Kirpich Equation (time of concentration).

Rational Method (NDMA guidance)

Peak runoff design with coefficient of runoff up to 0.95 for urban conditions.

Formula: Q = 10 × C × i × A (Q m³/hr; C runoff coefficient; i mm/hr; A ha).
Use composite C for mixed land uses via area-weighted average.
Imperviousness guide: Commercial/Industrial 70–90%; Res. High 61–75%, Low 35–60%; Parks 10–20%.

Kirpich Time of Concentration

Widely used for natural basins with defined channels; adjust for vegetated or urbanized sections.

Formula: Tc = 0.01947 × L^0.77 × S^-0.385 (Tc hours; L m; S = H/L).
Increase Tc by ~1.3–1.5 for undefined vegetated channels; decrease by ~40–60% for smooth urban channels.

Rainwater Harvesting (RWH) & Artificial Recharge – Basics

Collect rainwater for storage/use or recharge to reduce drain/nallah flows and arrest groundwater decline; many states mandate RWH in new construction; monitor performance.

Requirements: non-committed runoff; suitable hydrogeology/sites; cost-effective techniques.
Evaluate area selection, hydro-meteorology, hydrology, soil infiltration, aquifer geometry, and source water quality.
Techniques: surface (flooding, basins, stream augmentation), subsurface (recharge wells, pits/shafts), combination, indirect (induced recharge, aquifer modification).

High-Yield Summary

NUSP targets ODF cities, elimination of manual scavenging, and safe sewage & stormwater management.
Design wastewater at 100 lpcd (even though ~80% of supply reaches sewers).
Collection network design horizon: 30 years; pumping machinery: 15 years; STP & civil works: ~30 years.
DWWM typical design: ~15 years or present + 20% capacity.
Effluent pH: 5.5–9.0; BOD (inland/sewer/land/marine): 30/350/100/100 mg/L.
Oil & Grease limits: 10/20/10/20 mg/L (inland/sewer/land/marine).
Toilet flushing treated water: BOD 10 mg/L, RC 1 mg/L, Turbidity < 2 NTU.
Public toilets: spacing ~1 km, 50–50 M/F, disabled-friendly, 24×7, auto-clean ~40 s cycle (optional).
Rational Method: Q = 10CiA; urban runoff coefficient up to 0.95.
Kirpich: Tc = 0.01947 L^0.77 S^-0.385; adjust for vegetation (↑) and smooth channels (↓ 40–60%).
WSPS needs more land (0.8–2.3 ha/MLD) but has low O&M; compact processes (FAB/SAFF) suit space-constrained sites.
Septage: keep haul distance within 20–30 km; use STP or dedicated STDF as per land/availability.
Reuse: target at least 20% treated sewage reuse by volume in CSPs.
Heavy metals example (inland): Pb 0.1 mg/L, Cd 2.0 mg/L, Cr⁺⁶ 0.1 mg/L, Hg 0.01 mg/L.

MANIK Memory Tricks

“30–30–15–30–30” → Collection 30y, Pump station civil 30y, Pump machinery 15y, STP 30y, Effluent disposal 30y.
“80→100” → 80% water reaches sewers but design at 100 lpcd.
“pH 5.5–9.0: All” → Same pH band for all discharge categories.
“BOD 30/350/100/100” → Inland/Sewers/Land/Marine.
“Oil 10/20/10/20” → Oil & Grease mg/L: Inland/Sewers/Land/Marine.
“Flush 10; RC 1; Turb <2” → Toilet flushing targets.
“Q=10CiA” → Rational Method (m³/hr, mm/hr, ha).
“0.01947 · L^0.77 · S^-0.385” → Kirpich Tc (hours).
“PT @ 1 km, 50:50, 24×7” → Public toilets spacing, gender split, availability.
“Reuse ≥20%” → Treated sewage reuse target in CSPs.

Key Tables & Look-ups

Design Periods for Sewerage System Components (CPHEEO)
Component	Recommended Design Period	Clarification
Collection system (Sewer network)	30 years	Design for prospective population; replacement not feasible during service.
Pumping stations (Civil works)	30 years	Provide full civil capacity; plant duplication easier than civil augmentation.
Pumping machinery	15 years	Typical machinery life.
Sewage Treatment Plant (STP)	30 years	Construct in phases; initial flows may be lower than design.
Effluent disposal & utilization	30 years	Provisioning full design capacity upfront is economical.

Selected General Effluent Standards (Environment Protection Rules, 1986)
Parameter	Inland Surface Water	Public Sewers	Land for Irrigation	Marine/Coastal Areas
pH	5.5–9.0
Suspended Solids (mg/L, max)	100	600	200	—
Temperature	≤ 5°C above receiving water	—	—	≤ 5°C above receiving water
Oil & Grease (mg/L, max)	10	20	10	20
BOD (3 days @27°C) (mg/L, max)	30	350	100	100
COD (mg/L, max)	250	—	—	250
Lead, Pb (mg/L, max)	0.1	1.0	—	2.0
Cadmium, Cd (mg/L, max)	2.0	10	—	2.0
Hexavalent Chromium, Cr⁶⁺ (mg/L, max)	0.1	2.0	—	1.0
Mercury, Hg (mg/L, max)	0.01	0.01	—	0.01
Nitrate Nitrogen (mg/L, max)	10	—	—	20
Bio-assay test	90% fish survival after 96 h in 100% effluent

Treated Sewage – Upper Limits at Point of Use
Parameter	Toilet Flushing	Fire Protection	Vehicle Exterior Wash	Non-contact Impoundments	Horticulture/Non-edible Crops	Agriculture (Crops Raw/Cooked)
Turbidity (NTU)	< 2	< 2	< 2	< 2	< 2	< 2
Suspended Solids	Nil	Nil	Nil	Nil	Nil / 30	Nil / 30
Residual Chlorine (mg/L)	1	1	1	0.5	Nil	Nil
BOD (mg/L)	10	10	10	10	10 / 20	10 / 20
Faecal Coliform (per 100 mL)	Nil	Nil	Nil	Nil	Nil / 230	Nil / 230

Runoff Coefficients – Imperviousness Guide (NDMA)
Area Type	Imperviousness (%)
Commercial & Industrial	70–90
Residential – High Density	61–75
Residential – Low Density	35–60
Parks & Undeveloped	10–20

Terminology & Abbreviations

From this material only No outside expansions

Terminology (from text)

Open Defecation Free (ODF) — City condition where open defecation is eliminated.
Decentralised Wastewater Management — Wastewater collection/treatment/reuse near the source.
Centralized Wastewater Management — Conventional sewerage with city-wide collection and STPs.
Time of Concentration — Travel time from remotest point in basin to outlet.
Artificial Recharge — Techniques to augment groundwater using surface or subsurface methods.
Septage — Sludge and liquid removed from onsite sanitation systems (septic tanks/pits).
STDF — Septage Treatment & Disposal Facility referenced for septage management.

Abbreviations (from text)

NUSP — Mentioned as National Urban Sanitation Policy (2008).
CPHEEO — Central Public Health & Environmental Engineering Organisation (implied by manual title).
MoUD — Referenced as Ministry of Urban Development in the documents.
DWWM / DWMS — Decentralized wastewater management, described in MoUD guidelines.
CWMS — Centralized Wastewater Management System (used in comparison context).
WSPS — Waste Stabilisation Pond Systems (technology option).
UASB — Upflow Anaerobic Sludge Blanket Process (technology option).
DPS — Duckweed Pond System (technology option).
FAL — Facultative Aerated Lagoon (technology option).
TF — Trickling Filter (technology option).
BIOFOR — Biological Filtration and Oxygenated Reactor (technology option).
FAB — Fluidized Aerated Bed (technology option).
SAFF — Submerged Aeration Fixed Film (technology option).
CASP — Cyclic Activated Sludge Process (technology option).
STP — Sewage Treatment Plant (used throughout).
ULB — Urban Local Body (referenced in reuse decisions).
NDMA — Referenced as National Disaster Management Authority.
CGWB — Central Ground Water Board (referenced in AR manuals).
EP Act — Environment Protection Act context for standards (1986).
CSP — City Sanitation Plan context for 20% reuse target.

Examiner’s Favourites (Tricky Points)

Design wastewater at 100 lpcd even though expected inflow is ~80% of supply.
pH 5.5–9.0 holds for all discharge categories (inland/sewer/land/marine).
BOD 30/350/100/100 — keep the sequence correct (inland → sewers → land → marine).
Oil & Grease pattern 10/20/10/20 mirrors BOD category order.
Public toilets: spacing ~1 km and 50–50 M/F — easy to mix up.
Pumping station civil works 30y vs machinery 15y.
DWMS design period ~15 years vs centralized components often 30 years.
Kirpich Tc uses L^0.77 and S^-0.385 — exponents are common pitfalls.
NDMA urban runoff coefficient up to 0.95 — not 0.9 or 1.0.
Reuse target: at least 20% of treated sewage in CSPs — often overlooked.

Flashcards (tap to flip, then Next)

Card 0 of 0

Rapid-Revision Drill (7 minutes)

Read High-Yield Summary (90 sec).
Scan Tables (3 min) — Design periods, Effluent standards, Treated water limits, Runoff coefficients.
Run through Flashcards (2 min) — aim for 15+ cards.
Re-check MANIK mnemonics (30 sec).

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