Biofilm characteristics in natural ventilation trickling filters (NVTFs) for municipal wastewater treatment: Comparison of three kinds of biofilm carriers

Natural ventilation trickling filters (NVTFs) with three different carriers (sponge, zeolite and ceramsite) were used to treat domestic wastewater. All NVTFs with different biofilm carriers showed stable capability of COD removal and ammonia nitrification. The nitrification rate (NR), oxygen uptake rate (OUR), dehydrogenase enzyme activity (DHA) of biofilms were measured to investigate microorganism activity and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis was conducted to investigate the microorganism biodiversity. It was found that greater amount of biomass was attached on the sponge than those attached on ceramsite and zeolite, due to the large specific surface area of sponge. Large biomass may decrease the biofilm activity in the NVTFs. Compared with inoculated sludge, the biofilm in NVTFs had more abundant biodiversity after long-time domestication. Major DGGE bands of NVTFs were phylogenetically related to class Proteobacteria followed by Bacteroidetes, Nitrospirae, Cyanobacteria and Actinobacteria. The microorganism distribution in biofilm of zeolite NVTF was more similar with ceramsite, compared with sponge. As a biofilm carrier, zeolite showed no outstanding superiority on pollutants removal or nitrifying bacteria growing.