Improving the Performance of Attached-Growth Wastewater Treatment Processes by Altering the Support Media Surface

This study investigated the impact of altering the surface characteristics of support media used in attached-growth processes on the performance of biological wastewater treatment. The surface alteration was achieved through physical and chemical treatment of high-density polyethylene (HDPE), and changes in the HDPE surface characteristics, biofilm attachment, biofilm growth, and wastewater treatment performance were evaluated. Physical treatment procedures included roughening the HDPE coupons with sandpaper, and chemical treatment processes involved exposing the HDPE coupons to hydrogen peroxide and nitric acid. Changes in the physicochemical characteristics of the HDPE surfaces were determined using a variable pressure scanning electron microscope (VPSEM), a confocal profile meter, and contact angle (CA) measurements. The biofilm attachment, growth, and thickness were monitored using VPSEM images, biofilm volatile and total solids, protein quantities, and live/dead assay. The performance of biofilms in treating synthetic wastewater was determined by measuring the changes in chemical oxygen demand, ammonia, and total phosphorus concentrations. The results showed that physical treatment of the HDPE coupons increased the surface roughness and CA, changed the surface characteristics from hydrophilic to hydrophobic, improved the biofilm attachment and growth, increased the percentage of live cells, and enhanced the wastewater treatment performance. Chemical treatment of the HDPE coupons caused some minor changes to the surface and did not lead to significant improvements in biofilm growth or wastewater treatment.