The organic matter released from septic tanks can disturb the subsequent step in on-site
wastewater treatment such as the innovative filters for phosphorus removal. This study
investigated the effect of organic load on phosphorus (P) and bacteria removal by reactive
filter materials under real-life treatment conditions. Two long-term column experiments
were conducted at very short hydraulic residence times (average w5.5 h), using wastewater
with high (mean w120 mg L1
) and low (mean w20 mg L1
) BOD7
values. Two alkaline filter
materials, the calcium-silicate material Polonite and blast furnace slag (BFS), were tested
for the removal capacity of total P, total organic carbon (TOC) and Enterococci. Both experiments showed that Polonite removed P significantly ( p < 0.01) better than BFS. An
increase in P removal efficiency of 29.3% was observed for the Polonite filter at the lower
concentration of BOD7 ( p < 0.05). Polonite was also better than BFS with regard to removal
of TOC, but there were no significant differences between the two filter materials with
regard to removal of Enterococci. The reduction in Enterococci was greater in the experiment using wastewater with high BOD7, an effect attributable to the higher concentration
of bacteria in that wastewater. Overall, the results demonstrate the importance of extensive pre-treatment of wastewater to achieve good phosphorus removal in reactive bed
filters and prolonged filter life.