The effect of irrigation using recycled waters obtained from MBR and IDAL wastewater treatment systems on soil pH and EC under kikuyu grass (Pennisetum clandestinum) production

The main objective of this study was to determine the effect of irrigation using three different types of waters, viz. treated wastewater through membrane bioreactor system (MBR), treated wastewater via intermittently decanted aerated lagoon process (IDAL) and tap water (TW) on soil pH and EC under kikuyu grass production. No fertiliser was added during the study period (one year). Irrigation waters, waters extracted from different soil depths and soil samples from different depths were analysed in laboratory. Considerable changes occurred in soil characteristics over the study period under the various treatments. Soil pH increased more than 1 unit under irrigation with treated wastewater produced by IDAL system while soil irrigated with treated wastewater from MBR treatment system showed little change and TW irrigated soil evidenced a slight decrease when compared to pH at the beginning of the study. Also, a remarkable increase was recorded for EC1-5 of top soils irrigated with treated wastewaters compared to soil's initial EC. The results from this study highlighted the benefits of irrigation with treated wastewater through MBR system due to its lower cost of treatment compared to IDAL process while providing additional nutrients such as nitrogen and phosphorus form the wastewater.