The Government of India in 2008 approved for a 37 million litres per day Advanced Integrated Wastewater Oxidation Pond System (AIWPS) sewage treatment plant to be built in Varanasi to see if this technology can be the solution we’ve been waiting for. But they still haven’t released the funds so that the work can begin. They must begin to try out innovative technologies that will actually solve the sewage problems in the Ganga. In addition, the State government has approved for the building of a micro-tunnelling interceptor to catch all the sewage flowing into River Ganga at Varanasi.
A little more details on these solutions:
1. Ghat Interceptor Sewer
The construction of a riverside interceptor sewer pipe along the ghats of Ganga between the last line of buildings and the river from downstream of Nagwa Nallah to upstream of Varuna RiverThe interceptor will be constructed using proven micro-tunnelling technology that will not interrupt normal activities along the ghats. This will collect sewage from outflows that are currently going into Gangaji and convey this by gravity to an AIWPS sewage treatment plant proposed for construction at Sota.
The interceptor sewer is designed to be completely water proof and will divert sewage from the religious bathing areas along River Ganga in Varanasi during both wet and dry seasons.
2. Advanced Integrated Wastewater Oxidation Pond System (AIWPS)
For the treatment of sewage collected by the interceptor sewers and transported to Sota, construction of an AIWPS of 300 MLD capacity is proposed. AIWPS will completely treat the sewage, reclaim water and precious nutrients, require minimal electricity to operate, remove harmful disease causing pathogens and sequester carbon.
The AIWPS uses a series of four types of ponds:
- 6 Advanced Facultative Ponds (AFP)
- 12 High Rate Ponds (HRP)
- 24 Algae Settling Ponds (ASP)
- 3 Maturation Ponds
The Facultative Ponds consist of open ponds containing a methane fermentation pit. Sewage entering the system is injected at the bottom of the methane fermentation pit, where sludge is permanently trapped and consumed by fermentation.
The High Rate Ponds take water from the facultative ponds and aerobic bacteria break down dissolved organic matter. Oxygen is supplied photosynthetically by micro-algae. The rapid growth of algae raises the alkalinity of the water, killing pathogens.
In the settling ponds more than half of the algae produced in the high rate ponds settle out. Sufficient algae settle out to meet total suspended solids discharge requirements.
In the maturation ponds treated water is exposed to the sun’s UV rays and stored for irrigation or return the river.
The treated effluent has a coliform count below the permissible river water standard of MPN 500/100ml. It is rich in dissolved oxygen, odour free and colour free. The dried algal sludge is rich in nitrogen, phosphorus and potash and hence is an excellent fertilizer.
The total area of the system is estimated at 330 hectares. This land will be obtained by reclaiming a part of Sota sandbar by constructing dykes and low embankments. The resulting STP would be above flood level with only the final maturation pond being subject to minor inundation in a 1 in 100 year flood. This land is otherwise useless and is available at only a nominal cost. In addition the embankments proposed would provide two all weather access roads to the mainland for the 25,000 inhabitants of Dhab area during the monsoon months.