Significance of Ferric Chloride Addition on the Treatment Performance of Cloth-Media MBR Treating Municipal Wastewater

Municipal wastewater treatment saves fresh water resources from contamination and provides a sustainable approach for reuse in water-stress regions. Herein, the impact of ferric chloride addition to cloth-media MBR treating municipal wastewater was tested for treatment performance, membrane filterability and sludge particle size distribution. Dosing of 7.5 and 15 mg/l of FeCl3 did not show any significant impacts on the removal of chemical oxygen demand and ammonia compared to the control test. However, the addition of ferric chloride increases percentage removal of total phosphorous from 33.5 to 39.5 and 46.5% at doses of 7.5 and 15 mgFeCl(3)/l, respectively. The ferric chloride addition did not enhance membrane filterability or flocculation of the sludge particles. On batch and Jar test experiments, the removal of total phosphorous reached up to 86% at dose of 120 mgFeCl(3)/l which shows that each mg of P needs 8 mg of Fe (22 mgFeCl(3)). The batch and jar test experiments did not show any significant impacts of ferric chloride up to 120 mg/l on the biological activity and particle size distribution of the sludge. To enhance phosphorus removal in the MBR systems, coagulant addition to the final permeate is recommended to avoid any negative impacts on the flux rate and to minimize coagulant addition.

Automated summary

Municipal wastewater treatment is a sustainable method for protecting and reusing fresh water resources. This study found that adding ferric chloride can enhance the removal of total phosphorous, but it does not improve membrane filterability or sludge flocculation. To improve phosphorus removal in MBR systems, it is recommended to add coagulants to the final permeate.