Page 29 - Materials Chemistry, Second Edition

10 Life Cycle Assessment of Wastewater Treatment

TABLE 1.1
Various Colors of Wastewater and their Characteristics

Color Type Nature of Wastewater
Brown Industries Fresh condition
Grey Domestic wastewater Wastewater has experienced some level of decomposition
Black Septic systems Broad bacterial deterioration under anaerobic conditions has
taken place

septic systems. Wastewater in septic systems is highly noxious due to the hydrogen
sulfide produced during the decomposition of sulfate to sulfide by anaerobic micro-
organisms. Chemical compounds such as cadaverin, mercaptan, indol, and skatol
are the offensive compounds that produce a rotten smell during decomposition in
industrial wastewater.

1.4.1.3 Temperature
Temperature is one of the most important parameters to monitor in wastewater,
because the treatment of wastewater using microbes is commonly temperature lim-
ited. The temperature of the wastewater depends on the geographic location. The tem-
perature will range from 13°C to 24°C in the warmer provinces and from 7°C to 18°C
in the colder parts of the world. The higher temperature of wastewater affects the
aquatic organisms living in the water bodies by creating a deficiency of oxygen, which
reduces the reaction rate of the mixture and biological response rates. The wastewater
must be maintained at an optimal temperature, because a high temperature of waste-
water results in the growth of undesirable organisms, whereas when the temperature
drifts down, the treatment of wastewater becomes tedious and time consuming.

1.4.1.4 Solids
During the dissipation of wastewater at 103°C–105°C, some aggregate solid sub-
stances are deposited as residual debris. Wastewater contains suspended, volatile
suspended, and dissolved solids. Suspended solids increase the turbidity of the waste-
water, but they can be easily removed by subjecting the wastewater to a filtration
process. The other form of solids present in wastewater is volatile suspended solids,
which are made up of organic compounds such as carbohydrates, proteins, and fats.
They can easily be ignited at high temperature and affect the oxygen concentration of
the water resources. Settleable solids are another component of the wastewater, which
can be removed only by a sedimentation process. Most of the suspended solids are
settleable in nature, and a certain concentration of dissolved solids is also present in
the wastewater, which alters the characteristics of the wastewater (Muttamara, 1996).

1.4.2 cHeMical cHaracTerisTics of WasTeWaTer
Wastewater is basically composed of harmful gases, organic chemical compounds,
inorganic chemicals, and excessive nutrients. Gases such as methane, nitrogen, car-
bon dioxide, hydrogen sulfide, and ammonia are usually present in fresh wastewater