Abstract:
Wastewater disposal study was conducted in Blantyre City to establish status of wastewater disposal and determine volume of wastewater generated per residential land use category, and assess pollution impact of effluent from wastewater treatment facilities to the receiving surface water bodies in the city. A survey was carried out from June to August 2018 in twenty (20) areas in the city that were sampled using selective sampling technique. Four study areas were selected within each land use category as follows: Low density areas: Nyambadwe, Namiwawa, Sunnyside and British Central Area (BCA). Medium density areas: Chinyonga, Soche East, Namiyango and Manja. High-density areas: Mbayani, Nkolokoti, Nancholi and Misesa. Traditional housing areas: Ndirande Goliyo, Chilomoni Mthukwa, Manje and Chilobwe. Industrial areas: Makata, Ginnery Corner, Chirimba and Maselema. A multiple response research protocol was randomly administered to one hundred and eighty four (184) respondents within the study areas. The data collected from the survey was analysed using SPSSv20 Software to determine status of wastewater disposal and volume of wastewater released per land use category. Water quality assessment in effluent receiving rivers namely Mudi, Naperi, Limbe and Chirimba was carried out to determine magnitude of water contamination by wastewater. Water samples were collected from upstream and downstream points of a wastewater treatment plant (WWTP) of each river in the month of November 2018 for laboratory tests. Tests for Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Faecal Coliform Bacteria (FCB), Lead (Pb), Cadmium (Cd) and Chromium (Cr) as indicators of wastewater contamination were run and results were compared with standards set by World Health Organization (WHO) and Malawi Bureau of Standards (MBS). The results showed that 23.0% of the total wastewater generated in Blantyre City is directly disposed into the sewage system, 33.6% into septic tanks and pit latrines, 37.6% into storm water drains and 5.8% is disposed into rivers. Results further showed that high-density areas generate 14,475 m3 of wastewater per day, medium density areas 24,897 m3, low-density areas 43,712 m3 and informal traditional housing areas generate 9,298 m3 of wastewater per day. A total of 92,382 m3 of domestic wastewater is generated per day in the city of Blantyre. The laboratory test results for BOD5, COD, TSS, FCB, Pb, Cd and Cr in the water samples from the four rivers under study were higher than WHO and MBS guiding limits. Their mean levels differed significantly between the sampling positions (at statistical significance level, α = 0.05).
