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.