Low-Cost Technology for the Purification of Wastewater Contaminated with Pathogenic Bacteria and Heavy Metals

Abstract

Water scarcity has continuously increased over the last decades in countries like Egypt, where agriculture consume > 85% of the country’s water. Increased urbanization, industries, and expensive advanced treatment processes further aggravate this challenge, causing the use of poorly treated or untreated wastewater for crop irrigation. The current study investigated an eco-friendly technology consisting of a constructed wetland planted with Typha latifolia and Cyperus papyrus, with a zeolite substrate for water purification. In the unit containing T. latifolia, the removal efficiency of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and ammonia was 68.5%, 71%, 70%, and 82.3% when hydraulic retention time (HRT) was increased from day 1 to 3, respectively. In the unit planted with C. papyrus, the removal efficiency of COD, BOD, TSS, and ammonia was 85.5%, 86.2%, 83.9%, and 92.3% with an increase in HRT from day 1 to 3, respectively. Also, the microbial load was reduced by 99.9%, and complete removal of Salmonella sp. was achieved after 3 days with C. papyrus; with T. latifolia, the removal was 42.8–57.5%. Box–Behnken design was used to optimize the independent factors, including the initial concentration of metals (15 to 45 mg/L) and contact time (24 to 72 h). The removal efficiency of Cu and Zn was 93.4% and 94% at the optimum contact time (72 h), with 16 plant stems and 15 mg/L initial metal concentration. Overall, water from this simple-design and cost-efficient wastewater treatment technology could be reused for agricultural purposes without posing any health threats. This is particularly true with C. papyrus.