Effect of leachate effluent water reuse on the phytotoxicity and micropollutants accumulation in agricultural crops

Abstract

This research comparatively investigated the effects of effluents from three biological wastewater treatment systems on the phytotoxicity, seed germination, and accumulation of micropollutants and heavy metals in plants irrigated with the effluents under study. The three biological wastewater treatment systems were two-stage activated sludge (AS), two-stage moving bed bioreactor (MBBR), and two-stage moving bed bioreactor with microfiltration (MBBR/MF). The systems were operated in parallel with identical landfill leachate concentrations under different hydraulic retention time (HRT) (24, 18, and 12 h). The phytotoxicity experiments were carried out with golden pothos (Epipremnum aureum) planted in soil irrigated with AS, MBBR, and MBBR/MF effluent and those raised in the effluent (without soil). The malondialdehyde (MDA) concentrations in the plants were used to determine the plant stress. To evaluate the effect of water reuse to agricultural crops, this research measured the seed germination rates of lettuce (Lactuca sativa) irrigated with AS, MBBR, and MBBR/MF effluent and the accumulation of micropollutants and heavy metals. The results showed that under 24 h HRT, the AS, MBBR, and MBBR/MF systems could achieve high treatment efficiency of organics and nutrients and micropollutant degradation (73.4 – 100%). With shorter HRT (18 and 12 h), the treatment efficiency and micropollutant degradation of MBBR and MBBR/MF remained relatively unchanged (68.7 – 100%), unlike in the AS system. The MBBR/MF effluent exhibited the comparatively lowest MDA concentrations. Furthermore, the MBBR/MF effluent minimally affected the growth of lettuce, as evidenced by highest seed germination rates. No micropollutants and heavy metals were present in lettuce irrigated with MBBR/MF effluent. However, traces of bisphenol A and di-(ethylhexyl)-phthalate were detected in lettuce watered with AS and MBBR effluents. As a result, the MBBR/MF system is operationally and environmentally ideal for treating landfill leachate for high-quality effluent which can be reused to irrigate crop and replenish surface water. © 2021 Elsevier Ltd