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