RESOURCE. RECOVERY FROM SEWAGE TREATMENT PLANTS (STPs)

Abstract

Resources are diminishing due to the vast utilization of Energy for meeting day to day demand in the 'competition and threats' environment. Exponential growth of population further puts pressure on energy heavily. Biologically produced energy has been identified as an attractive alternative to the increasingly scarce fossil fuel supplies. Resource recovery from waste fetches revenue and makes the environment safe and healthy. Since the Energy Recovery from Sewage Treatment Plants is of the nature of 'non conventional' i.e. 'renewable energy source', it is eco friendly and increases sustainability. The use of renewable energy makes the environment 'clean and green'. The recoverable items in solid, liquid and gaseous forms from STP's and their values are explained in this dissertation. We have an opportunity to take a more holistic approach to pollution by dealing with liquid and solid waste streams, and reducing their combined environmental impacts on water, land, and air. We can recover from sewage treatment plants: ➢ Biodiesel from fat, oil and grease ➢ Biogas from other organic material ➢ Biodiesel from residual sludge ➢ Fertilizers and metals from inorganic materials ➢ District heating through sewage-source (water-source) heat pumps >. Water for reuse from water discharged The Municipalities of Indian towns are utilising the sewage sludge for biogas generation and producing electricity. They utilise the treated effluent for irrigation and reuse for industrial purposes. They also sell the sludge cake as manure. Aquaculture is also being practiced. The case studies are made in Chennai, Haridwar, Lucknow, Pimpri Chinchwad-Pune, Saharanpur, Sonepat, Rishikesh and Periyakulam town sewage treatment plants. Chennai and Haridwar have ASP based STP's. , Lucknow and, Pune have UASB based iv STP's. Saharanpur and Sonepat have FAB based STP's. Rishikesh and Periyakulam have WSP based STP's. The ASP and UASB based sewage treatment plant are biogas producing plants. The FAB and WSP based plants are not capable of producing biogas. But the produced gases are not fully utilised. Most of the gases are flared up. So, it should be monitored to utilise the full strength of biogas and reduce the electricity charges to be paid to the electricity board. The WSP based sewage treatment plants are well maintained leading to prevention of pollution of the river and at the same time drawing the full opportunity to recover the cost by way of resource recovery. From the net present worth analysis of resource recovery, it is found that, the most economical option is WSP in the areas having availability of land with low cost (upto Rs. 60.00 Iakhs/hectare). In the areas of high land cost (over Rs. 60.00 lakhs/hectare), then the UASB based technology is the economic option. If O& M Charges are properly monitored, ASP technology will also be economical. FAB technology is costlier than the other technologies. With acute shortage of land and higher degrees of treatment, FAB technology may be adopted. With the increase in land demand, Batch Reactor based treatment technology may be a good option. I!