Abstract
The main purpose of this investigation was to assess, in situ, the hourly abundance dynamics of enterobacteria and total heterotrophic aerobic bacteria (THAB), over a daily period, in 3 wells in Yaounde region, Cameroon. Sampling was done weekly, for 4 months. Water samples were collected in sterile glass bottles and incubated in situ for 2 h, 4 h, 6 h, 8 h, 10 h and 12 h. Isolation and enumeration of enterobacteria and THAB were performed on MacConkey agar (Bio-Rad) and standard agar (Bio-Rad) media, respectively, using the plate count method. Using a linear regression model, ln(number of CFUs) was plotted against time. The slope of each regression line was considered as the apparent increase or decrease in cell number. Concentrations of THAB and enterobacteria varied from 9.90 to 14.19 and 4.09 to 9.59 ln units·ml-1, respectively, in W1, from 9.90 to 14.25 and 3.00 to 5.39 ln units·ml-1 in W2, and from 9.90 to 14.00 and 6.55 to 11.51 ln units·ml-1 in W3. For the first 6-hour incubation period at all of the sampling points, the cell apparent growth rate (CAGR) varied from 0.023 to 0.262 h-1 for THAB and from 0.001 to 0.315 h-1 for enterobacteria; cell apparent inhibition rate (CAIR) varied from 0.015 to 0.615 h-1 for THAB and from 0.015 to 0.604 h-1 for enterobacteria. In the second 6-h incubation period, the CAGR varied from 0.010 to 0.822 h-1 for THAB and from 0.015 to 0.771 h-1 for enterobacteria; the CAIR varied from 0.015 to 0.260 h-1 for THAB and from 0.007 to 0.338 h-1 for enterobacteria. The values of physico-chemical parameters recorded before incubation displayed temporal and spatial variation over the sampling period. Bacterial abundance dynamics in some cases was significantly correlated to some of these abiotic factors. The abundance of the microorganisms decreased initially but later increased.
Highlights
Water losses in the distribution system are categorised as either real losses or apparent losses
Universal metering refers to systems where meters have been installed on all properties and billing is based on the volume of water used rather than on flat rate billing
This study focuses on the Kampala Water Distribution Network (KWDN)
Summary
Water losses in the distribution system are categorised as either real losses (leakage) or apparent (commercial) losses. Most studies carried out on metering have been based on water utilities of developed countries, with well-managed water distribution networks, notably the USA, Spain, France, and Italy (Arregui et al, 2006a; Criminisi et al, 2009; Pasanisi and Parent, 2004; Richards et al, 2010). The number of service connections with meters of size 15 mm is about 92% of the total service connections (or 141 675 service connections) These connections represent a sizeable investment for the utility and are mainly domestic users and small commercial customers. The amount of water unmeasured in Kampala by DN 15 mm meter sizes (both working and failed meters) was estimated at an average of 58 m3/meter-year This is rather high compared to average figures of 19 to 49 m3/meter-year reported for a study done on 2 water utilities in the USA (Male et al, 1985). Water supply is irregular in most parts of Kampala city and asset management practices are inadequate (Mutikanga et al, 2009)
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