Intensification of wastewater treatment with polymer fiber-based biofilm carriers

Biofilm containing fix-bed systems are frequently applied for intensifying biological treatment in wastewater purification. In these operational units a lot of different biofilm carriers have been used and tested; among them, however, the polymer fiber-based materials are barely investigated. The authors studied four carriers: three types of polypropylene (PP) fibers and a polyester (PES) fiber were compared relating their physical–chemical characteristics and biofilm colonization properties. For the physical–chemical characterization surfactants release, wettability, methylene blue bromophenol blue and protein (bovine serum albumin) adsorption were measured as well as the surface charges of the biofilm carriers were determined by zeta potential examinations.Colonization experiments were carried out in a pilot plant scale biological municipal wastewater treatment system consisting of eight cascade reactors for 18 days. Each of the four tested fibers were placed into the reactors, and biofilm colonization was followed by measuring the dry biomass content and TTC (triphenyl tetrazolium chloride) enzyme activity of the biofilms adhered to the polymer fibers. During the colonization experiments pH, chemical oxygen demand (COD), concentration of total suspended solids (TSS), various nitrogenous compounds and dissolved oxygen were also monitored in the water phase of the reactors.Among the four different fibers one of the PP carriers turned to be the most favorable in colonization tests. This carrier, having surface and wetting properties differing from the other ones colonized the maximum biofilm mass, and the biofilm grown on this fiber had also the highest total enzyme activity all along the purification process, both in organic material degrading and in nitrifying reactors.

► Four different polymer fiber-based carriers were studied.
► Connections between biofilm adhesion and surface properties were investigated.
► A correlation was found between wettability and colonization properties.
► Polypropylene was found to be better in colonization properties than polyester.