Effect of treated greywater by black shale and laterite on Lactuca sativa L. germination rate

Abstract

Greywater reuse for agricultural irrigation may contribute to reduced use of chemical fertilizers, and is helping to conserve scarce freshwater source. However, treatment methods that reduce the harmful effects of untreated greywater are essential for sustainable agriculture. This study aims to evaluate greywater treatment by geo-materials (shale and laterite) and to investigate the germination rate of lettuce. Batch experiments were used to monitor sodium removal from greywater using shale and laterite (36 g.L−1 and 5.63 g. L−1 respectively) as adsorbents. The study monitored sodium removal from greywater during the batch experiments. The results showed that the two geo-materials could be used as low cost-effective adsorbents for treating greywater to satisfy the WHO standard for irrigation water. Furthermore, the results indicated that shale and laterite were successful in removing Na from raw greywater. A kinetic study revealed that maximum Na adsorption occurred in 120 and 240 min for the laterite (1.2 mg. g−1) and the shale (0.184 mg. g−1) respectively. Furthermore, germination rates obtained with raw greywater and greywater treated by shale were higher than 50%, while the lower germination rates were observed when irrigating with tap water (28%) and greywater treated by laterite (33%).