Waste water management – A Key Building Block of the smart city

Abstract

The term’ smart cities ‘is treatment between governments, urban planners and even the private sector to address the projected difficulties of cities in the future. Smart cities encompass six important sectors that necessity to work in agreement to achieve a common goal of construction a city more functional, sustainable and efficient for its residents. These sectors are smart energy, small addition, smart public services, smart mobility, smart buildings and smart water or waste water management. Here we will discuss that how waste water can be recycled after proper treatment. Waste water consists of 99.9% of water and 0.1% of solids. These objects are mostly organic with small portion of inorganic matter and pathogenic bacteria, algae, fungi, viruses, protozoa etc, which are answerable for many water borne diseases. The following processes are common for waste water treatment. (1) Preliminary or physical treatment consist of Removal of lighter floating material that’s leaves, pieces of rags, wood charcoal etc.; fats and grease; and heavier suspended inorganic material like grit, sand etc.  All these are done is Skimming tank, Detritus tank and Grit chamber. (2) Primary treatment is given in settling or sedimentation tank for removal of larger suspended organic solids. Primary treatment usually can remove up to 60% of suspended solids and about 35% of BOD from waste water but this relatively low level of treatment. (3) Secondary or Biological treatment consists of removal of fine suspended and dissolved organic material by means of biological flocculation and precipitation by intermittent Sand filter or Trickling filters. Final settling of organics is done in Activated sludge treatment plant and secondary settling tanks. (4) Tertiary or advance treatment means polishing, the effluents from the secondary treatment to improve its quality. The effluent from secondary stage is passed into flocculation tank where lime is added to eliminate phosphates. Then liquid goes to ammonia stripping tower. Here Nitrogen present as Ammonia is converted to gaseous form at high pH. The remaining organic materials are removed by adsorption on Activated Charcoal and finally chlorination for disinfection. The final liquid is fairly clean having BOD (< 1ppm), PO₄^3- (0.2-1 ppm) NH₄⁺ (0.3-1.3 ppm).This treated water can be used for all activities safely accept drinking purposes.