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IS 7935:1989 is the Indian Standard (BIS) for criteria for design of waste stabilization ponds (first revision). This standard provides criteria for the process design and construction of waste stabilization ponds (WSPs) for treating domestic sewage and biodegradable industrial wastewater. It covers the design of anaerobic, facultative, and maturation ponds, specifying key parameters like organic loading rates, detention times, depths, and temperature correction factors.
Lays down the criteria for the design of waste stabilization ponds for the treatment of domestic sewage and industrial effluents.
! The CPHEEO Manual on Sewerage and Sewage Treatment is a more current and widely used reference that supplements or supersedes some recommendations of this code.
! Pond performance is highly dependent on ambient temperature, which significantly affects the BOD removal rate constant (k). Designs must consider the lowest expected monthly average temperature.
! Proper siting is crucial to avoid nuisance; consider prevailing wind direction, distance from habitation, and land availability as per Clause 3.4.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
wastewatersewagesoilalgaebacteria
International Equivalents
Similar International Standards
DWA-A 201E:2017German Association for Water, Wastewater and Waste (DWA), Germany
HighCurrent
Principles for the Dimensioning, Construction and Operation of Ponds for the Treatment of Domestic and Municipal Wastewater
Provides comprehensive design, construction, and operational criteria for pond systems, mirroring the scope of IS 7935.
Design Guidance (Mara, 2004)World Health Organization (WHO) / University of Leeds
HighCurrent
Domestic Wastewater Treatment in Developing Countries (Book by D.D. Mara, contains globally accepted WHO design principles)
A de-facto global standard providing detailed design equations and criteria for all types of stabilization ponds.
WEF MOP No. 8Water Environment Federation (WEF), USA
MediumCurrent
Design of Municipal Wastewater Treatment Plants (Relevant chapters on stabilization ponds)
A broad manual for wastewater plant design, with chapters on ponds that cover similar design principles but within a wider context.
Key Differences
≠International standards like DWA-A 201E and WHO guidelines use process-based kinetic models for design, especially for pathogen and nutrient removal, which are temperature-dependent. IS 7935 relies more on empirical formulas and loading rates linked to latitude as a proxy for temperature.
≠Modern international standards provide more detailed guidance on sludge accumulation rates, sludge management, and desludging frequency for anaerobic and facultative ponds, reflecting a greater emphasis on long-term operation.
≠More recent international codes offer more specific and stringent guidance on the use of geosynthetic clay liners (GCLs) and geomembranes to ensure groundwater protection, whereas the 1989 Indian standard focuses primarily on traditional clay liners.
≠International guidance, particularly from Europe (DWA), includes more explicit design considerations for nitrogen and phosphorus removal, which is a less prominent aspect of the IS 7935 design criteria.
Key Similarities
≈Both IS 7935 and international standards use the same fundamental classification system for ponds: Anaerobic, Facultative, and Maturation (or Polishing) ponds in series.
≈The primary design parameter for facultative ponds in both Indian and international guidelines is the surface organic loading rate (in kg of BOD per hectare per day), which is linked to solar radiation and temperature.
≈Key construction features such as minimum freeboard, embankment slopes, and requirements for inlet/outlet structures to prevent short-circuiting are broadly consistent across all standards.
≈The use of Hydraulic Retention Time (HRT) as a critical design parameter, especially for maturation ponds to achieve a desired level of pathogen removal, is a common principle.
Parameter Comparison
Parameter
IS Value
International
Source
Organic Loading Rate (Facultative Pond)
Based on latitude, e.g., 220-300 kg/ha.d for 20-30°N
Calculated by temperature formula, e.g., λ = 20T - 60 (where T=coldest month temp in °C)
WHO Design Guidance (Mara, 2004)
Volumetric BOD Loading (Anaerobic Pond)
0.1 to 0.4 kg/m³.d
0.1 to 0.35 kg/m³.d (Varies with temperature, from <10°C to >25°C)
WHO Design Guidance (Mara, 2004)
Depth (Anaerobic Pond)
2.5 to 5.0 m
2.0 to 5.0 m
WHO Design Guidance (Mara, 2004)
Pathogen Removal Model (Maturation Pond)
Based on recommended HRT of 3-5 days per pond
Based on first-order kinetic models (e.g., Marais equation) using temperature-dependent decay constants (k_t)
DWA-A 201E:2017
Embankment Slope (Inner, unlined)
Not steeper than 1V:3H
1V:3H to 1V:5H, depending on soil stability and maintenance access
WEF MOP No. 8
Minimum Freeboard
0.5 m
0.5 to 1.0 m (higher end for large ponds with significant wind fetch)
DWA-A 201E:2017
Depth (Facultative Pond)
1.5 to 1.8 m
1.5 to 2.0 m
DWA-A 201E:2017
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Recommended depth of anaerobic pond2.5 to 5.0 m
Recommended depth of facultative pond1.5 to 1.8 m
Recommended depth of maturation pond1.0 to 1.5 m
Typical detention time in anaerobic pond2 to 5 days
Permissible surface BOD loading for facultative ponds (25°C)200 to 300 kg/ha/day
Recommended inner side slope for ponds1V:2.5H to 1V:3H
Minimum freeboard for ponds0.5 m
Key Formulas
A = (Q * Li) / Ls — Area of facultative pond based on surface loading
kt = k20 * (1.05)^(T-20) — Temperature correction for BOD removal rate constant (k)
V = Q * t — Volume of pond based on detention time
t = (log(Ni) - log(Nt)) / kb — Detention time in maturation pond for pathogen removal (simplified)
Tables & Referenced Sections
Key Tables
Table 1 - Permissible BOD Loading for Facultative Ponds
Table 2 - Values of First Order Rate Constant (k) for BOD Removal at Different Temperatures
Table 3 - Typical Coliform Removal in a Series of Maturation Ponds
What is the main design basis for a facultative pond?+
The primary design basis is the permissible surface organic loading in kg of BOD per hectare per day, which is a function of temperature. Refer to Clause 5.2 and Table 1.
What is the purpose of maturation ponds in a WSP system?+
Their primary function is pathogen removal, particularly fecal coliforms, to ensure the final effluent is safe for discharge or reuse. Design is based on detention time for bacterial die-off (Clause 6).
What is the recommended depth for an anaerobic pond?+
The recommended depth is 2.5 to 5.0 meters to ensure anaerobic conditions are maintained and to provide volume for sludge digestion (Clause 4.3).
What freeboard should be provided for the pond embankments?+
A minimum freeboard of 0.5 meters above the maximum water level should be provided as per Clause 7.1.1.