Analysis of some Selected Heavy Metals and COD Along Nairobi River

Water pollution has been one of major problem in most of our natural sources of water. This has come as a result of increased human activities which is not matched with development of infrastructure to deal with waste disposal. The main sources of water pollution are industrial discharge, sewage, agricultural waste, fertilizer and poor disposal of garbage. Nairobi River is one of natural source which has been affected by pollution as a result of rapid industrialization and growth in population. Therefore, there is a need to regularly do assessment of water quality in Nairobi River in terms of heavy metal concetrations.Heavy metals are natural components of the earth crust and they cannot be degraded or destroyed. Heavy metals can a water supply through industrial and consumer waste or even from acid rain breaking down soils and releasing heavy metals into streams, lakes, river and ground water. To small extend they enter our bodies via food, drinking contaminated water and high ambient air concentrations near emission sources. As trace elements some heavy metals e.g. copper, selenium, zinc are essential to maintain the metabolism of the body. However in high concentrations may lead to poisoning of the body. Heavy metals are dangerous because they tend to bioaccumulation.

The study focused on analysis of heavy metals in water from Nairobi River. Water from Chiromo, Gikomba,outer ring road and kariobagi along Nairobi River was analysed for the presence of the following metals, Cadmium(Cd),Copper(Cu),Manganese(Mn),Lead(Pb),Zinc(Zn).The concentration of metals was determined using AAS analytikjene contr model AA 700. For Cd,   Pb were below detection limit, manganese concentrations ranged from1.04 - 4.16mg/,copper0.05- 0.09mg/l and zinc was0.01- 0.07mg/l.The PH was between 7.15-7.45,TDS range was 193-253 mg/l, COD ranged from 37.6-125.7(average) and conductivity was 394-506µ/s.

Metal concentration increased downstream. There were case of Mn,Zn and cu pollution thus raising issue of concern. TDS and Conductivity increased downstream. COD decreased downstream. Therefore proper control mechanism should put down to ensure the quality of water from Nairobi River.

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