13 Some more stringent standards have been developed recently to deal with the removal
of nutrients and the priority pollutants. When the wastewater is to be reused, standards normally include the requirements for the removal of refractory organic, heavy
metals, and in some cases dissolved solids [22]. Hence, in order to achieve the regulation standard, the effluents from the industries have to be treated appropriately
before discharging into the environment.
2.2.2 Wastewater Characteristics
Based on the constituents present in wastewater, it can be characterized as physical, chemical and biological. The physical characteristics mainly include the presence of
suspended solids in the effluent, degree of turbidity, temperature, color, and odor. Whilst, the chemical characteristics may include the organic compounds e.g.
carbohydrates, phenol, pesticides, dissolved gases e.g. hydrogen sulfide, methane, oxygen, and inorganics e.g. alkalinity, heavy metals, nitrogenous substances, pH,
etc. [22 – 23]. Organic impurities are the most common and important constituent in
domestic and industrial wastewater. Quality of wastewater is determined by the characteristic of wastewater and commonly the organic impurities consist of the
mixture of carbonaceous material not specific. Therefore, the investigation of organic content in the wastewater is not an easy test. The most commonly used tests
are the total organic carbon TOC, chemical oxygen demand COD, and biochemical oxygen demand BOD
5
[25]. The biological characteristics include the presence of bacteria, viruses, algae, protozoa, worms, coli forms, etc. Basically,
bacteria are used in several wastewater treatment processes particularly for the degradation of biodegradable contaminant. However, the growth of the bacteria
especially pathogenic ones which transmit disease that may cause gastrointestinal symptom must be controlled. During the aerobic biodegradation of biodegradable
contaminant by bacteria, the oxygen is required. Algae are an important supplier for oxygen in the ponds during their photosynthesis. The schematic diagram of
wastewater characterization is shown in Figure 2.3.
14 Natural gas sweetening process will generate high concentration of amine in
wastewater and the concentration of amine may reach as high as 15 – 50 by weight
in practice [13]. Hence, the wastewater from the gas processing unit needs to be treated before discharging into the environment [26
– 27].
Figure 2. 3 Constituent of wastewater.
2.2.3 Wastewater Treatment Methods
