The effects of irrigation with reclaimed wastewater on heavy metal accumulation and plant development in lettuce

Abstract

Due to the increasing growth of the city, agricultural land has begun to take place in and around the living areas. This situation also increases the need for irrigation water available in agriculture. This study assessed the impacts of lettuce irrigation with treated effluents, as compared to domestic water (DW) irrigation, on plant physiological structure and crop productivity. The treated effluents reused for irrigation were produced in two Municipal Wastewater Treatment Plants utilizing two discrete tertiary treatments (physical purification and biological treatment). The experiment was conducted for five months on the agriculture form by using lettuce leaf type and head type lettuce. In all plant groups (the productivity, weight, length, diameter, root fresh and dry weight, root diameter), quality characteristics (deformable and number of marketable leaves per plant, total chlorophyll) and heavy metal contents (Ni, Pb, Cd, and Co) were determined. Application of treated wastewater (TWW) increased marketable yield, the number of leaves per plant, plant height, and diameter. The highest yield of lettuce plants was obtained with the treated wastewater in head type lettuce. TWW irrigation also increased the growth parameters such as the number of leaves, fresh root weight, dry weight, and total chlorophyll. Results show a high influence of TWW in nitrate content of lettuce. Results on Ni, Pb concentrations show higher values for "Festival" (leaf type) and "Bombola" (head type) plants irrigated with TWW than DW. Cd and Co values in the plants subjected to DW and TWW were similar. The values of total leaf chlorophyll content in all plants irrigated with TWW were higher than for those irrigated with DW. Results show that heavy metal accumulation, an important criterion for the use of treated waste water in agriculture, may differ in lettuce varieties. By choosing heavy metal tolerant varieties, treated wastewater can be used for long-term in sustainable agriculture.