Wastewater management in small towns – understanding the failure of small treatment plants in Bolivia

<p>Wastewater management in developing countries is a challenge, especially in small towns with rapid population growth. This study aims at assessing the performance and management of five treatment plants (TPs) in rural areas of Cochabamba, Bolivia. Pollutants’ concentrations, wastewater flows, hydraulic and organic loads and hydraulic retention times were determined in three small treatment plants (2000–10,000 population equivalent [p.e.]; flow > 432 m³/d) and two very small treatment plants (<2000 p.e.; flow < 432 m³/d). The performance assessment was based on operational parameters, treatment efficiency and effluent quality. Management data were collected through semi-structured interviews with managers of local water associations. The results support that the poor performance of the TPs is due to lack of operational expertise and financial resources for adequate operation and maintenance (O&M). Additionally, effective treatment was affected by the type of technology used and whether the plant design included plans for O&M with available resources. This study contributes to a better understanding of actual operating conditions of wastewater TPs in small towns, thus providing needed information regarding technology selection, design, implementation and operation.</p

Community structure of the experimental plots during ozone exposure at 0, 90 and 120 ppb and after transplanting under common ecological conditions.

<p>Community structure of the experimental plots during ozone exposure at 0, 90 and 120 ppb and after transplanting under common ecological conditions.</p

Means and statistics from analysis of variance of species richness (<i>S</i>), species diversity (Shannon-Weaver index, H´) and species evenness (<i>H</i>´/log_e (<i>S</i>)) for arthropod communities established from different historic exposure regimens.

<p>Means and statistics from analysis of variance of species richness (<i>S</i>), species diversity (Shannon-Weaver index, H´) and species evenness (<i>H</i>´/log_e (<i>S</i>)) for arthropod communities established from different historic exposure regimens.</p

Relative abundance of <i>Spergula arvensis</i>, <i>Calandrinia ciliata</i> and other species in plant communities selected under different episodic concentrations of tropospheric ozone.

<p>Ozone concentrations in the open top chambers during long-term exposure were 0 ppb (white bars), 90 ppb (grey bars) and 120 ppb (dark bars). Data represents species abundances during the first (a) and second (b) year of experiment after original soil seed bank was transplanted to a common natural field environment. Relative abundance for each plant species was calculated as the summed abundances of each plant species for a particular year/total number of seedlings recorded in the plot (n = 3). Error bars represent standard error. Year a ANOVA <i>P</i> _species < 0.01, <i>P</i>_ozone 0.016, <i>P</i>_{species x ozone} 0.034; year b ANOVA <i>P</i> _species < 0.01, <i>P</i>_ozone 0.024, <i>P</i>_{species x ozone} 0.042</p

Mean seedling density in 1 m² plots established from plant communities. selected under different episodic concentrations of tropospheric ozone (0, 90 and 120 ppb).

<p>Mean seedling density in 1 m² plots established from plant communities. selected under different episodic concentrations of tropospheric ozone (0, 90 and 120 ppb).</p