This compendium of sewage treatment technologies by the Indian Institute of Technology (IIT), Kanpur has been prepared, based on primary and secondary data gathered from operation of sewage treatment plants (STPs) in the country over the last two decades.

Various available treatment options have been categorized and specific recommendations made regarding various technological options for sewage treatment in the various regions. Though the study is based primarily on the sewage treatment technologies adopted in the Ganga basin, the experience of other parts of the country has also been incorporated to develop the guidelines.

As regards STPs in the Ganga basin a wide range of technologies have been adopted such as Waste Stabilization Ponds (WSPs), Duckweed Pond Systems (DPS), Karnal Technology, Facultative Aerated Lagoons (FAL), Trickling Filter (TF), Activated Sludge Process and its modifications (ASP), BIOFOR process, ASP BIOFOR-F process, Fluidized Aerated Bed (FAB) process, Submerged Aerated Fixed Film (SAFF) process, rotating Biological Rope Contractor (RBRCX) process, Upflow Anaerobic Sludge Blanket (UASB) process and Down Hanging Sponge Bio-tower (DHSB) process.

According to the Compendium, 32 STPs totaling 728 MLD treatment capacity were constructed and 11 existing STPS (151 MLD treatment capacity) were renovated under the Ganga Action Plan Phase I (GAP-1). Activated sludge process (ASP) was the most preferred technology, with ASP and its minor variants accounting for almost 62 per cent of the total capacity.

26 STPs (722 MLD treatment capacity) were set up under the Yamuna Action Plan, Phase I (YAP-I). Upflow Anaerobic Sludge Blanket (UASB) process was the most preferred treatment technology, accounting for 83 per cent of the total installed treatment capacity.

Concurrently with YAP, 30 STPs having 2325 MLD of sewage treatment capacity were added in Delhi under the river conservation programme of the Government of NCT Delhi. Most of these STPS are based on ASP technology or its minor variants. A large STP (182 MLD capacity) has been constructed at Rithala using the BIOFOR-F technology.

In addition to the technological options discussed above, several other technologies have been used with success in various parts of India. These include the Sequential Batch Reactor (SBR) technology and its minor modification known as the CTECH process, which has been employed in several places in western and southern India. Another promising technological option is the moving Biological Bed Reactor (MBBR), which is very similar to the FAB system. Further in many places in western and southern India, the UASB process has been used in conjunction with FAL and a Final Polishing Unit (FPU) or in conjunction with the ASP process to provide high quality treatment.

The categorization of the treatment technologies has been done in the Compendium based on comprehensive analysis of performance and cost data from a large number of sewage treatment plants in the Ganga river basin and elsewhere employing all the technological options mentioned above. The treatment technologies have been divided into four categories. This classification may not be universal, but is certainly valid based on experience with wastewater treatment plants over the two-three decades in India in general, and the Ganga basin in particular.