Page 205 - AJWEP-22-6

Performance of Kalobe waste ponds, Mbeya

1. Introduction theoretically capable of achieving significant reductions
in biochemical oxygen demand (BOD), chemical
Effective wastewater treatment is essential for oxygen demand (COD), and total suspended solids
safeguarding public health and environmental quality, (TSSs), its performance in terms of nutrient removal
particularly in urban centers of low- and middle- and final effluent quality has raised concerns in recent
income countries where infrastructure expansion often years. 7,12
lags behind population growth. Urban wastewater Globally, WSPs in warm climates have demonstrated
1-3
management in Sub-Saharan Africa is often constrained high treatment efficiencies for organic matter (BOD,
by limited financial resources, poor planning, and COD) and suspended solids. However, challenges persist
outdated infrastructure, leading to frequent treatment in nutrient and pathogen removal. 6,7,13 In Sub-Saharan
failures and environmental contamination. Waste cities, treated effluent from WSPs is sometimes reused
4
stabilization ponds (WSPs) have gained prominence as for irrigation and aquaculture, necessitating stricter
an affordable, low-maintenance solution for municipal effluent standards to protect public health. Ammonia
14
wastewater treatment in such contexts due to their removal in WSPs is often temperature-dependent,
reliance on natural treatment mechanisms, minimal and without adequate aeration or nitrification steps,
operational requirements, and resilience to hydraulic most ammonia persists in the final effluent. Regular
15
and organic load fluctuations. Their design and sludge removal and continuous influent monitoring
5,6
application follow well-established principles suited are essential to sustain WSP performance and prevent
to tropical climates, making them ideal for many pond overloading. At Kalobe WSPs, elevated levels
7
Sub-Saharan African countries. 7,8 of BOD, total dissolved solids (TDS), and nutrients
WSPs are widely adopted in developing regions in the final effluent indicate that process inefficiencies
because of their simple operation and ability to handle and intermittent shock loads from industrial discharges
variable influent loads without the need for complex may be limiting the system’s ability to meet Tanzania’s
mechanical equipment. In Tanzania, many urban areas effluent discharge standards. 16
6
rely on WSPs as the primary treatment technology. This study aims to assess the stage-wise performance
Mbeya city, located in the southern highlands of of the Kalobe WSPs using field data collected at the
Tanzania, is served by the Kalobe WSPs, which treat inlet and outlet points of the anaerobic, facultative,
a mixture of domestic and industrial wastewater. The and maturation ponds. Six key parameters, which are
system was designed to accommodate 28,800 m /day BOD, COD, TSS, ammonia (NH –N), nitrite (NO ⁻–N),
3
3
2
of wastewater; however, actual inflows vary between and TDS, were analyzed to determine individual and
15,000 and 18,000 m /day depending on rainfall and cumulative removal efficiencies. The study further
3
industrial activity. Major contributors to the influent examines how flow variability, influent composition,
load include large beverage industries such as Tanzania and industrial contributions affect treatment outcomes.
Breweries Limited (TBL), Coca-Cola Kwanza, and Findings from this evaluation are expected to inform
Pepsi, which are required to pre-treat their wastewater future infrastructure upgrades, industrial compliance
before discharging it into the municipal system. enforcement, and integration of tertiary treatment
9
However, evidence suggests that these pre-treatment options to improve the overall system efficiency.
processes are inconsistently effective, resulting in high
influent organic and nutrient loads that compromise the 2. Materials and methods
WSP’s performance. 10,11 2.1. Description of the study area
The Kalobe WSP system comprises a series of The Kalobe WSPs are located at 8°55’S, 33°28’E
anaerobic, facultative, and maturation ponds arranged (UTM Zone 36S; Easting 9,014,865.14 m; Northing
sequentially. These primary units are complemented 544,767.03 m) in Mbeya city, situated in the southern
by a preliminary screening chamber, grit channel, highlands of Tanzania. This study was conducted during
sludge drying beds, and a natural wetland that serves the dry season (April 2025); therefore, the results should
as a polishing component. Anaerobic ponds facilitate be interpreted as baseline dry-season conditions rather
sedimentation and biological degradation under anoxic than a full annual performance assessment. The facility
conditions, while facultative ponds support both aerobic receives wastewater from both municipal sources and
and anaerobic processes. Maturation ponds provide major beverage industries, including TBL, Pepsi, and
final polishing, primarily targeting pathogen and Coca-Cola Kwanza. The system comprises two anaerobic
nutrient reduction before discharge. While the system is ponds, four facultative ponds, and one maturation pond,

Volume 22 Issue 6 (2025) 199 doi: 10.36922/AJWEP025320249