During last decades, when public sector in India had achieved commanding heights, industrial townships were planned, habitats classified as clusters, neighbourhoods, sectors and town. The dwelling units were largely designed as two or three storeys or multi-storeyed. Land Plots were later auctioned, allowed to be built by private developers. The dwelling unit concepts were reshaped as high rise buildings came to be accepted. The sky line began changing. The large residential complexes came to be known as cities, and thus became cities within cities.. The infrastructure planning and designing got specialised split into vertical infrastructure (plumbing), and horizontal infrastructure. This paper touches horizontal configurations where water resource engineers can participate with advantage.
The Central water commission, the nodal authority in water resources at centre and WRDs at state level, require to create new units dealing with urban waters including reuse of waste waters for urban needs and for industrial water reuse applications. Open flow hydraulic design is replaced by Pipe and pressure flow design practice. Water Resource Engineers need to assist water utilities in master planning, reuse of waste water and storm water. The evaluation also establishes the need for a closer linkage in Global water partnership programme. Long distance water transfers, with pressured piped and pumping systems, the extraction of surface water intake designs and conveyance system design from rivers and even from ground water (like Great Man-Made River project in Libya) are well documented. Re-enginnering of river systems in Rhine, Danube and Thames in Europe are known examples of this partnership programmes, where pollutions in the reciving waters was contained, waste waters were treated and reused. Experience in treatment of effluents from tanneries, dairy industry, distilleries, paper and pulp had been of interest to Indian engineers, for some time.
Within municipal limits of most Indian cities, lies another recognised source of liquid wastes. The biometanation/anaerobic digestion processes for treatment are well known. The aspect so far ignored has however been, the industrial reuse of effluents/urban waters on large scale for sustainability and resource recovery. These waters are now included in inventory of new sources of water supply. It is true that small industrial units are getting larger, the effluent from the units experience changes in quantity and quality. It is also true that electricity outages makes the treatment plants unreliable. New industrial plants raise new issues, call for appreciation for water use water recycling practices.
State pollution control Boards are groomed into enforce measures adopted for Zero Waste discharges in industrial liquid wastes, internal recycling and reuse of precious resources like water. The approval of statutory or urban local bodies is however also required. There are no regulations, which make it mandatory for ULBs, to explore energy water resource regeneration, from these wastes. The schemes financial subsidies and incentives for such ventures through Ministry of Non Renewable Sources of Energy, as well with Ministry of Urban Development. exist, and yet investments are not commercially popular, with investors. With increasing population, per capita demand and aggravating polluting loads from wastes, shortage of waters, urban infrastructure services including water, waste water and storm water infrastructure management have emerged, a discipline on its own merits.
Liquid Effluents in current urban environments are predominently of two types;
– Domestic/Municipal – Industrial
Municipal wasted liquid effluents, including effluents from sugar, milk and brewery units contain lot of organic materials. This effluent is utilised for generating methane gas. Both aerobic and anaerobic digestion process are well known. Aerobic systems require substantial quantum of electrcal energy, large sized containment vessels. Anaeobic treatment marks a significant step forward, in savings in costs, industrial liquid wastes generally take place at various temperatue levels. Some of these contain chemical like dyes, caustic soda and inorganic salts. They may also contain toxic heavy metals, mercury, coal dust, iron ore etc. Temperatures may range from 40c to 100c. Recovery of heat from liquid effluents pose design problems, due to their corrosive and erosive nature. Recent advances in the materials technology, have enabled recovery of heat from effluents having temperature of 45c. Teflon tubes are used as heat exchangers. In the early ninetees, setting up of industrial estates in India, became the buzz word. Public sector organisations like NIDC, have since been wound up. A few consulting engineering firms were active in designs of effluent treatment plants. Along with municipal liquid waste from domestic habitats, the storm water drains have emerged another source but are great carriers of pollutions. State and central pollution control Boards undertake monitoring of their disposal plans.
