Evaluation of the effectiveness of immobilization of activated sludge on composite materials “polyethylene:polysaccharides”

Abstract

The aim of this work is to study the immobilization ability of new composite materials based on polyethylene (PE) and polysaccharides (PS) in relation to the biocenosis of activated sludge (AS). The objects of the study were selected composite materials of the following composition: PE : pure microcellulose (MCc), PE : waste microcellulose (MCw), PE : starch (ST), at a ratio of components PE : PS = 70:30 wt.%. The objectives of the study were to determine the main morphological parameters of new composites (porosity, roughness, density), assessment of hydrochemical and hydrobiological state of AS (silt index, mass concentration of silt, species composition) until it locks into composites, assessment of the immobilization ability of the studied materials by biomass weight gain, monitoring of the state of AS after fixing. The tests found that the composite of structure of PE : MCc of has a density of 410 kg/m3 and a porosity of 60%, the roughness of 3.5; the composite of structure of PE : MCw has a density of 590 kg/m3 and a porosity of 40%, roughness of 2.0, composite of structure of PE : ST has a density of 640 kg/m3 and a porosity of 50%, the roughness of 2.5; wherein the reference sample - PE - has the parameters: density 860 kg/m3 and a porosity of 0%, roughness 0. To determine the immobilization capacity of the new composite materials, a laboratory experimental immobilizer was used, which is a container filled with 70% of the useful volume of the active sludge suspension and 30% of the floating loading samples. Immobilization was carried out under aeration conditions during 2, 4, 8, 12, 24, 48, 72 hours. As a result of tests it is established that the sample of structure of PE : MCc for 72 hours of immobilization showed a gain of biomass of the order of 12%, the sample of structure of PE : MCw - 5%, the sample of structure of PE : ST – 7%, PE – 3%. The condition of the organisms AS after fixing was evaluated by washings with immobilized samples, as a result of microscopy of washouts, the presence of living representatives of the biocenosis of AS in all samples was established, but they differ in number: for the sample of structure of PE : MCc - numerous, PE : MCw, PE : ST - average number, PE - small number. Further studies on the modification of the synthetic polyolefin matrix by functional fillers, including those from a number of polysaccharides, are of interest, allowing to increase the affinity of the carrier material with the extracellular matrix of activated sludge.