Evaluation of Occurrence, Concentration, and Removal of Pathogenic Parasites and Fecal Coliforms in Three Waste Stabilization Pond Systems in Tanzania

Abstract

In Tanzania, waste stabilization ponds (WSPs) are employed to treat wastewater, and effluents are used for urban agricultural activities. The use of untreated or partially treated wastewater poses risks of disease transmission, including parasitic and bacterial infections, to exposed communities. Little is known about the occurrence, concentration, and removal of parasites and fecal coliform (FC) bacteria in WSPs in Tanzania. This study evaluates the occurrence and concentration of parasites and FCs in wastewater, the efficiency of WSPs in removing parasites and FCs, and the validity of using FCs as an indicator of parasites. This was a cross-sectional study conducted between February and August 2018. Wastewater samples were collected from three WSPs located in the Morogoro, Mwanza, and Iringa regions. APHA methods were used to test physicochemical parameters. The modified Bailenger method and Ziehl–Neelsen stain were used to analyse parasites. Membrane filtration method was used to analyse FCs. Data were analysed using IBM SPSS version 20. Helminth egg removal ranged from 80.8% to 100%. Protozoan (oo)cyst removal ranged from 98.8% to 99.9%. The Mwanza WSP showed the highest FC reduction (3.8 log units (100 mL)−1). Both the parasites and FCs detected in the effluents of assessed WSPs were of higher concentrations than World Health Organization and Tanzania Bureau of Standards limits, except for helminths in the Morogoro WSP and FCs in the Mwanza WSP. FCs were significantly correlated with protozoa (p < 0.01) and predicted protozoa occurrence well (p=0.011). There were correlations between physicochemical parameters, parasites, and FC bacteria in the WSP systems. Inadequate performance of these systems may be due to lack of regular maintenance and/or systems operating beyond their capacity. FC indicators were observed to be a good alternative for protozoa monitoring, but not for helminths. Therefore, during wastewater quality monitoring, helminths should be surveyed independently.

Evaluation of contaminants removal by waste stabilization ponds: A case study of Siloam WSPs in Vhembe District, South Africa

“…The discharge of such effluent will not only affect the aesthetic property of the receiving water course but increase the risk of parasitic infection on anyone who swims in the water (Amoah et al, 2018;Gumbo et al, 2010). Under optimal conditions, E. coli removal by WSP systems can be up to 6 log reduction but most WSP systems usually report about 2-3 log reductions of faecal coliforms (Zacharia et al, 2019;Verbyla et al, 2017;Olukami and Duscoste, 2011). Results from this study did not show notable log reductions of pathogens in the wastewater and this is a potential threat to the water quality of the receiving stream.…”

“…Under optimal conditions, E. coli removal by WSP systems can be up to 6 log reduction but most WSP systems usually report about 2–3 log reductions of faecal coliforms ( Zacharia et al., 2019 ; Verbyla et al., 2017 ; Olukami and Duscoste, 2011 ). Results from this study did not show notable log reductions of pathogens in the wastewater and this is a potential threat to the water quality of the receiving stream.…”

Evaluation of waste stabilisation pond units for treating domestic wastewater

“…Since algae were observed in the facultative and maturation ponds, these might have elevated the pH through photosynthesis, which consumed more carbon dioxide than the bacteria could restore through respiration. Carbonate and bicarbonate dissociation increased the concentration of the hydroxyl group which slightly raised the pH (Zacharia et al ., 2019). The lowest pH was recorded in the anaerobic pond and this might be due to anaerobic conditions producing gases such as hydrogen sulphide and production of acids therefore lowering the pH.…”

“…The COD was within the range of 200–235 mg L −1 reported by Zacharia et al . (2019) who evaluated the occurrence, concentration, and removal of pathogenic parasites and FC in three WSPs. High COD indicates a high amount of organic matter which will reduce DO in surface waters and be detrimental to aquatic life because of anaerobic conditions.…”

Natural Wastewater Treatment Systems for Prevention and Control of Soil-Transmitted Helminths

“…However, sometimes WSP effluents have reported higher concentrations of STH eggs than that recommended by the WHO. Two out of five assessed WSP systems in Tunisia gave out effluents with more than one Ascaris lumbricoides eggs per liter [46], while one WSP in Tanzania and one WSP in Cayman Islands generated effluents with more than one hookworm eggs per liter [31,47].…”