Effectiveness of Constructed Wetlands for Post-treatment of Mixed Wastewaters from Poultry Slaughterhouse and Olive Mill

Abstract

The quality standards of treated wastewater have become more stringent in recent times, which led to high costs and energy that are required to reduce pollution loads from municipal wastewater. Constructed wetlands (CWs), an alternative to mechanized wastewater treatment technologies, have lower capital expenditures with low annual running costs (low energy and personal demands). A pilot system of vertical flow constructed wetlands (CWs) planted with Phragmites australis species was installed and operated after two UASB reactors at Birzeit University campus, Palestine. The study aimed at investigating the efficacy of the pilot CWs system as a post-treatment stage of anaerobically pretreated mixed industrial wastewater from poultry slaughterhouse and olive mill under variable mixtures. For a period of 6 months (May-October, 2020), the CWs pilot system (four beds with 3 m2 each) was monitored at average loading rates for COD (64.6-145 g/(m2.d) and for TKN (21.4-34.4 g /(m2.d). Further, the potential of heavy metals accumulation in CWs vegetation was assessed. We argue that nature-based solutions are environmentally sound options for high-quality effluent reclamation that comply with Palestinian technical regulations for effluent reuse in agricultural irrigation purposes. The results of the research will lead to closing the gap in circular bioeconomy pertinent to efficient use of water recycling in beneficial uses, thus contributing to achieving the water-food-energy-security in Palestine. The findings of this research study included the following: • The constructed wetland system, under investigation, showed a good performance in the removal of organic and inorganic pollutants in agrifood industrial effluents (COD, TSS, TKN, heavy metals, and total phenols). • The purification efficacy of CWs for mixed industrial water from olive presses and poultry slaughterhouses was satisfactory with high removal percentages (95% - 99%). • The constructed wetland system achieved average removal rates for COD (33.2-67.7 g/(m2.d) and for TKN (10.5-21.2 g /(m2.d). • In a semi-arid country, the constructed wetlands produced treated water of high quality with the possibility of water reuse in landscape and agricultural irrigation. Anaerobically pre-treated agrifood industrial wastewaters (poultry slaughterhouse and olive mill press) were successfully treated, over a period of six months (May-October 2020), using a pilot-scale constructed wetland system. Optimizing the system operation and long-term investigations warrant further exploration to ensure compliance of treated water with local reuse standards and ensure safe disposal into receiving environment.