This study investigated the effects of population
growth on the performance of the targeted wastewater
treatment plants in Sedibeng District and Soshanguve periurban
area, South Africa. The impact of population growth
was assessed in terms of plant design, operational capacity
(flow rate) and other treatment process constraints.
Between 2001 and 2007, the number of households connected
to the public sewerage service increased by 15.5,
17.2 and 37.8 % in Emfuleni, Lesedi and Midvaal Local
Municipalities, respectively. Soshanguve revealed a 50 %
increment in the number of households connected to the
sewerage system between 1996 and 2001. Except for
Sandspruit (-393.8 %), the rate of influent flows received
by Meyerton increased by 6.8 ML/day (67.8 %) and
4.7 ML/day (46.8 %) during the dry and wet seasons,
respectively. The flow rate appeared to increase during the
wet season by 6.8 ML/day (19.1 %) in Leeuwkuil and
during the dry season by 0.8 ML/day (3.9 %) in Rietgat.
Underperformance of the existing wastewater treatment
plants suggests that the rapid population growth in urban
and peri-urban areas (hydraulic overloading of the
wastewater treatment plants) and operational constraints
(overflow rate, retention time, oxygen supply capacity of
the plants and chlorine contact time) resulted in the production
of poor quality effluents in both selected areas.
This investigation showed that the inefficiency of Meyerton
Wastewater Treatment Plant was attributed to the
population growth (higher volumes of wastewater generated)
and operational constraints, while the cause of
underperformance in the other three treatment plants was
clearly technical (operational)