Electroflocculation – Constructed Wetland Hybrid for Improved Phosphate Removal In Effluent Reuse

Reusing or recycling wastewater for stream rehabilitation require discharge of high quality effluent complying with strict nutrient standards as well as development of feasible treatment alternatives. Constructed wetland is already a proven technology for efficient polishing wastewater effluent except for phosphorous. We investigated the coupling of Electroflocculation (EF) with constructed wetland (CW) for improved contaminants removal, phosphorous in particular, from secondary effluents. The work consisted of three phases: electro-jar testing, continuous-flow EF-filtration (GF)-CW bench scale experimentation and field, half-industrial piloting. P, turbidity, TSS and TOC were particularly monitored. Laboratory experiments showed that EF-GF effectively removed phosphate (96%), while CW effectively removed organic matter (85%). Therefore, it seemed that the coupling of both unit processes would combine their treating abilities. Field pilot results show that EF-GF removed up to 97% of total phosphorus, resulting in P concentrations of <0.4 mg/L, which are extraordinary results by any comparison. In addition to phosphorus removal, the system is capable of meaningfully reducing some of the TOC (53%) and most of the TSS. The hybrid action is explained by combining flocculation and adsorption mechanisms produced by the EF with transport, attachment and biodegradation mechanisms in the CW beds.