CHAPTER 2 LITERATURE REVIEW
2.1 Industrial wastewater
Metcalf and Eddy 1991 defined wastewater as a combination of liquid and water which carry the wastes that are removed from residence, institution and
industry, together with such ground water, surface water, and storm water. When untreated wastewater is allowed to accumulate, the decomposition of organic material
lead to the production of malodorous gases. Wastewater also contains numerous pathogenic or disease-causing microorganisms. The nutrient rich wastewater that
enters the aqueous ecosystem leads to eutropication, which still causes oxygen depletion. It is also toxic to the aquatic life and responsible for methemoglobinemia
when it is contaminated to the drinking water.
2.1.1 Wastewater characteristics
Industrial wastewater is characterized in term of physical, chemical and biological constituents. The important physical properties are color, odor and
dissolved substances. While the chemical constituents may include organic compounds such as carbohydrates, phenol, pesticides, etc, gases such as hydrogen
sulfide, methane, and oxygen; and inorganic such alkalinity, heavy metals, nitrogenous substances, pH, etc, the biological constituents may contain various
species, protista, virus, etc Metcalf and Eddy, 1991.
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Organic chemicals are important constituents in municipal as well as industrial wastewater. This characteristic has become one of the important concerns
in determining the quality of wastewater. Moreover, the organic chemicals usually are not specific and consist of mixture of many different carbonaceous materials. As a
consequence, test for organic content of such wastewater is not specific. The most commonly test used biochemical oxygen demand BOD and chemical oxygen
demand COD. However, much attention is also focused on nutrients especially nitrogen and phosphorous that are contained in the wastewater Eckenfelder and
Musterman, 1995.
2.1.2 Wastewater Regulation
Wastewater treatment is primary developed in response to the concern for public health and adverse condition caused by the discharge of wastewater to the
environment Metcalf and Eddy, 1991. The purpose of the treatment process is to remove suspended and floatable material, treatment of biodegradable organics and
other contaminants, as well as elimination of pathogenic organism.
In order to maintain an acceptable quality of wastewater in terms of its characteristics, different countries have enacted their respective regulation specifying
the maximum admissible values of the parameters. The Malaysian standard for industrial effluent is presented in Table 2.1. Some more strict standards have been
developed recently to deal with the removal of nutrients and priority pollutants. When the wastewater is to be reused, standards normally include requirements for removal
of refractory organic, heavy metals, and in some cases dissolved solids Metcalf and Eddy, 1991. Consequently to achieve the effluent standard regulation, industries
have to treat the wastewater appropriately before disposal. Alternatively, industries are able to arrange a contract with third party for treatment the wastewater.
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Table 2.1 Malaysian effluent standard regulation for sewage and industrial effluents,
environmental quality act 1974 [Laws of Malaysia; act 127. 1999]
Parameters Unit
Standard A Standard B
Temperature ˚C
40 40
pH value -
6.0 – 9.0
5.5 – 9.0
BOD5 at 20˚C mgL
20 50
COD mgL
50 100
Suspended Solids mgL
50 100
Phenol mgL
0.001 1.0
Free chlorine mgL
1.0 2.0
Sulphide mgL
0.50 0.05
Oil and grease mgL
Non detectable 10.0
2.1.3 Wastewater treatment Methods
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