Assessment of water quality of two wetlands - Chemu and Laloi Lagoons - in the Tema Export Processing Zone
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Date
2000-02-01
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Abstract
Physico-chemical and microbiological studies were conducted on two wetlands, Chemu II and Laloi Lagoons, in the Tema Export Processing Zone (Lat. 5° 39’N 5° 45’N, Long. 0o – 0o 05’E) between March 29 and May 3, 2000 in order to assess their water qualities.
For Chemu Lagoon, temperatures averaged 32°C and pH 8.4. Very high levels of colour and turbidity, 302°H and 62 FNU respectively, were recorded. Very low salinity of 4.7°/oo and high TSS of 776 mg/l was also recorded. DO level averaged 1.9 mg/l with anaerobic conditions in the main body of the lagoon. BOD5 and COD levels stood at 133mg/l and 585mg/l respectively. Nutrient levels were quite high (P04-P = 1 .2mg/l, N03-N = 1 .3mg/l, N02-N = 0.5mg/I). Fluoride level of 1 .4mg/i and very high faecal coliform count of 1.62 x 107 per 100ml were also recorded. Trace metal levels recorded were very high (Cd = 0.012mg/I, Cr6+ = 0.22mg/l, Pb = 0.45mg/l, Hg = 5.3mg/l).
As regards the Laloi Lagoon, temperatures averaged 31oC and pH 8.1. Low colour and turbidity levels, 12°H and 3.3 FNU respectively, were recorded. Very high salinity of 18°/oo and TSS of 2751 mg/l (mainly deposit of salt) were also recorded. DO level averaged 9mg/l. BOD5 and COD levels stood at 30mg/I and 425mg/i respectively. Low nutrient levels were recorded (PO4-P = 0.25mg/l, N03-N = 0.07mg/l, N02-N = 0.01mg/l). A fluoride level of 1 .4mg/l was also recorded. Faecal Coliform count averaged 2020 per l00ml. Unexpectedly high trace metal pollution was observed (Cd = 0.06mg/l, Cr6+ = 0.26mg/l, Pb = 0.42mg/l, Hg = 6mg/l).
To restore the valuable resources of the lagoons and protect human health, it is recommended that the Chemu Lagoon be dredged; bio-accumulation of trace metals in fishes and shellfishes in the Laloi Lagoon be investigated; and also, standards for safe disposal of industrial and municipal waste be vigorously enforced.
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A Thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science & Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Water Supply and Environmental Sanitation, 2000