Coupled UASB-constructed wetland system for reuse of wastewater for gardening irrigation

A coupled anaerobic baffled reactor-constructed wetland system was used for the treatment of wastewater from a research center, whose composition is different from domestic wastewater due to its origin. The anaerobic baffled reactor was used at full scale (20 m3) while the constructed wetland with sugar cane and heliconia plants was used at pilot scale (1.36 m3). System efficiency was measured in terms of organic matter removal as chemical oxygen demand (COD) and biochemical oxygen demand (BOD5), total suspended solids (TSS) and total and fecal coliforms. The lowest organic matter concentration of 22 mg/L was found at day 140 in the system effluent; it was slightly higher than the Mexican regulation for gardening irrigation, although it complies with the European regulation for water B class that can be used for irrigation of alimentary crops which are not in contact with the water, irrigation for crops for processed foods or irrigation for cattle food. The removal of TSS and coliforms with the system was higher than 90%, thus it compares well with similar systems and effluent concentrations and complies with European and Mexican regulation for gardening irrigation. Concentrations of organic matter such as COD and BOD5 in the effluent of the wetland were 22 mg/L (slightly higher than Mexican regulation but compliant with the European regulation for water class B) at 140 days of operation. Concentrations of TSS (10 mg/L) and total coliforms (93 MPN/100 mL), positively compared with other systems and complied with the European and Mexican regulations. Using the coupled anaerobic baffled reactor-constructed wetland system it was possible to remove TSS and coliforms in compliance with European and Mexican regulations for gardening irrigation; however, organic matter removal as BOD5 must be improved.