Pollution and Self-Cleansing of an Urban River in a Developing Country: A Case Study in Dar es Salaam, Tanzania

Pollution and self-purification trends of an urban river namely, Msimbazi River, in Dar es Salaam City, Tanzania, were investigated. Site investigations and water quality analyses were done. The river is polluted in terms of high organic and nutrient concentrations, low dissolved oxygen, and high counts of indicator organisms. Biochemical oxygen demand (BOD₅) concentrations were 27– 340 mg/L. Dissolved oxygen was found to be as low as 0.9 mg O₂/L. Bacteriological pollution increased with distance downstream of the river, a trend attributable to an increase in the catchment of pollution sources, which are on-site sanitation systems. Although the river has an appreciable self-purification capacity, the capacity is strained by persistent pollution overloads. The pollution plight of the river is attributable to its being flanked by expanding human habitats and vibrant industrial, institutional, and socio-economic activities. Provision for pretreatment of discharges into the river is put forward as a remedial measure for the observed pollution. Matching nontechnical and techno-social remedial measures are also recommended. These include sensitization of polluters on merits of environmental protection practices such as cleaner production and strict enforcement of environmental protection laws.     

Recycling inorganic domestic solid wastes: results from a pilot study in Dar es Salaam City, Tanzania

Solid waste recycling and recovery approach can be a sustainable and effective waste management system in many growing cities of the least developed countries. In the course of achieving proper solid waste management, a lot of efforts in these countries have, however, been focused more on collection and disposal and ignored waste recycling which can result into income generation, employment creation and reduction of the waste quantities that will finally require disposal in the existing municipal landfills or disposal sites. This paper reports the findings of a study on solid waste recycling in a selected semi-planned settlement in Dar es Salaam City, Tanzania. The objective of the study was to describe the existing solid waste management in the study area with a view to identifying the waste generation rates, types of the wastes and determine the amount of waste from the settlement that can be recycled for the purpose of income generation and reduction of the total amount of waste to be disposed of. Findings from this study revealed that waste generation rate in the study area was 0.36 kg per person per day, and that out of the 14 600 kg of recyclable waste generated per year, 8030 kg or 55% can be recycled and generate a per capita income of Tsh 834 000 for waste recyclists which is more than twice the official minimum annual wage (Tsh 360 000) in Tanzania at the time of the study. The study also revealed that effective waste recycling in the study area would result in the reduction of the total waste that need to be transported for final disposal by 11%.     

Applicability of a Septic Tank/Engineered Wetland Coupled System in the Treatment and Recycling of Wastewater from a Small Community

A septic tank (ST)/engineered wetland coupled system used to treat and recycle wastewater from a small community in Dar es Salaam, Tanzania was monitored to assess its performance. The engineered wetland system (EWS) had two parallel units each with two serial beds packed with different sizes of media and vegetated differently. The larger-sized medium bed was upstream and was planted with Phragmites (reeds) and the smaller-sized medium bed was downstream and was planted with Typha (cattails). The ST/EWS coupled system was able to remove ammonia by an average of 60%, nitrate by 71%, sulfate by 55%, chemical oxygen demand by 91%, and fecal coliform as well as total coliform by almost 100%. The effluent from the ST/EWS coupled system is used for irrigation. Notably, users of the recycled irrigation water do not harbor any negative feelings about it. This study demonstrates that it is possible to treat and recycle domestic wastewater using ST/EWS coupled systems. The study also brings attention to the fact that an ST/EWS coupled system has operation and maintenance (O&M) needs that must be fulfilled for its effectiveness and acceptability. These include removal of unwanted weeds, harvesting of wetland plants when the EWS becomes unappealingly bushy, and routine repair.     

Assessment of performance of solid waste management contractors: a simple techno-social model and its application

Despite being in operation for more than 7 years now, privatised solid waste management (SWM) service in Tanzania has not been formally assessed. This is the premise for the techno-social performance assessment model for SWM contractors, which is presented in this paper. This paper outlines the background of SWM privatisation in Dar es Salaam City in addition to describing and demonstrating the application of the assessment model. The model has three components: service beneficiaries' assessment sub-model, service area technical assessment sub-model, and contractors' attributes sub-model. The model can be used to assess the performance of SWM contractors and in so doing provide data for assessing SWM privatisation as a whole. In the application of the model presented in this paper scores for 5 assessed contractors are in the range 24-65%. The contractor who scored highest is also the most experienced and also the best equipped. Nevertheless, all contractors scored poorly with the respect to their ability and attributes in SWM mainly because most of them are new to the solid waste management field.