Zero Liquid Discharge Plant of IIT Hyderabad
The Green Initiative
IIT Hyderabad has set up comprehensive wastewater and solid waste management system on its campus. From banning the usage of paper cups, replacing packed water with UV water dispensers, setting up of waste segregation and recovery facilities, bio-digester, and sewage treatment plants to growing more than 15000 trees in last 2 years IIT Hyderabad has considerably reduced its carbon footprint and is making every effort to turn its campus into a green and sustainable habitat. All the buildings are designed to meet GRIHA green buildings rating 4 and are energy efficient by using performance double glazed units for the windows and façade, use of occupancy sensors to save energy, ensuring sufficient day light in all the rooms. Hostels have radiant cooling systems. The campus has a considerably large solar farm of 0.95MWp capacity. Even the water taps in the residential areas have been attached with water-saving adapters which have significantly reduced the water bill.
The masterplan of the campus has been developed with an objective to create a ‘zero discharge campus’. Open earthen swales have been constructed to efficiently discharge the surface runoff while allowing percolation into the soil during the water transport. These swales would discharge the runoff to the lakes created at the lowest contoured pockets of the campus.
IIT Hyderabad also developed a few recharge wells across the campus.
These measures are aimed at conserving the rainwater as well as the groundwater.
The Sewage Treatment Plant (STP)
The present STP was established in July 2019. IIT Hyderabad has two sewage treatment plants in its Master Plan. Both the treatment plants have modular designs. Each plant has three modules. Each module has a capacity of treating 650 kilo liters of sewage per day. The civil work of both the STPs have been completed. However, the electromechanical works of only one module of the STPs has been completed and operationalized so far to cater to the present days’ demand. The expansion of the STPs will be achieved through the phase-wise completion and commissioning of the successive modules upon occupancy of the buildings. Scheduling of such expansions will be based on the growth of the campus. At present, IIT Hyderabad has close to 3500 students and about 241 faculty members. Many faculty and staff members reside on campus with their families.
The sewage treatment plant of IIT Hyderabad receives wastewater from the hostels, canteen, kitchen/dining hall, Academic buildings, and the faculty & staff towers. The sewage is collected and transported to the STP through an elaborate sewer network under gravity.
Major points of generation of sewage (a) Hostel; (b) Academic and Administrative Buildings; (c) Residential Towers, (d) Dining Hall
The design of the STP has been based on Membrane Bioreactor technology. The wastewater is collected in a collection sump which is common for the present as well as future modules. Water is pumped from the collection sump to made to pass through a screen chamber followed by a grease trap. The screen chamber has two components. Large size particles including floating debris are removed by a 16 mm coarse screen. This is followed by a 6 mm fine screen to remove smaller particles. Fat, oil, and grease is then removed from the wastewater using a belt-type skimmer. The wastewater flows under the gravity into an equalization tank from which the wastewater is pumped into the biological treatment units. The wastewater is screened through a 2mm punched hole screen before it reaches the biological treatment units.
The biological treatment units consist of an anoxic chamber followed by an aerobic chamber. The anoxic chamber is meant for the removal of nitrogen, whereas in the aerobic chamber organic carbon is biologically oxidized to carbon dioxide and ammonical nitrogen is oxidized to nitrates. The mixed liquor from the aerobic chamber is led into a membrane tank that houses cassettes of hollow-fiber membranes. The treated water is drawn through the membrane and the solids are separated. The permeated is disinfected in a chlorine contact tank. The portion of the permeate undergoes a softening treatment before being used in air-conditioning system. The remaining portion of the treated water is used for toilet flushing and horticulture. Biosolids, generated in the biological treatment units, and other organic particles are collected in a sludge holding tank. The sludge is then centrifuged to remove the excess water. The water is sent back to the equalization tank and the dewatered sludge is subjected to drying. The dried sludge is used for gardening purpose. Recently, IIT Hyderabad has set up a compost facility; the aim is to mix the sludge with other organic wastes and convert to compost before being used for gardening.
The treated effluent is as good as potable water. The image below shows the quality of sewage before and after treatment.
The sewage treatment plant at IIT Hyderabad produce a treated effluent that is used for non-potable purposes that include flushing toilets, gardening, and is also used in air-conditioning systems. The sludge, generated in this process, has horticulture application.
Figure 5: Treated water is used in plantation
Process flow diagram