Due to the rapid urbanization, wastewater has been continuously and excessively released into the environment, causing significant impacts on human and wild life. Many organic compounds in municipal wastewater are detected in different types of wastewater, affecting water quality, human health and biodiversity in the ecosystems. These compounds have significant impacts on receiving water bodies so as finding an appropriate treatment technology to effectively remove organic matters (OMs) in wastewater is very essential. Recently, moving bed biofilm reactor (MBBR) has brought increasing research interest in practice for removal of biodegradable organic matter and its application have undergone various degrees of modification and development. Moreover, as the carrier using in the MBBR is playing a crucial role in system performance, choosing the most efficient carrier could enhance the MBBR performance. Hence, scientists have been looking for an appropriate carrier which is not costly and has a suitable surface for microbial growth. The main aim of this study is to evaluate a specific MBBR with polyethylene media as biofilm support carrier in terms of OMs removal along with nutrient removal and microbial growth and activity.
The optimization study for its practical application was conducted through a series of the investigations on the effect of carrier’s filling rate, organic loading rate (OLR) and hydraulic retention time (HRT). The carrier used in this study was made of Poly Ethylene (PE) with a density of about 0.95 g/cm³. The experimental results show that although increasing carrier filling rate from 10 to 40% resulted in augment of attached biomass from 0.95 to 5.0 mg/g, microbial activity was dramatically decreased from 2.22 to 0.25 mg O₂/g MLVSS.h. Thus, the best MBBR performance was achieved when the SOUR was at the peak of 5.04 O₂/g MLVSS.h at 20% of filling rate with the removal efficiencies of 95.33, 92.13, 57.41 and 67.58% in terms of DOC, COD, PO₄-P and NH₄-N, respectively. Moreover, 19.8% increase in DOC removal was resulted from the increasing amount of biomass from 5.68 to 11.96 mg/g due to the OLR increase from 0.15 to 0.8 kg COD/m³d, respectively. Besides, 48.19% of TN removal was achieved at the highest OLR of 0.8 kg COD/m³d in which microbial activity was 8.53 mg O₂/g MLVSS.h. The effect of HRT on OMs and nutrients removal efficiency was also investigated and the results reveal that at all of the HRTs, more than 95% and 96% of DOC and COD removal efficiency was achieved, respectively. In addition, the experimental result show that at HRT of 4 h, the lab scale MBBR had an average TN removal efficiency of 60.58% while it was only 48.2 and 42.15% at HRT of 8 and 25 h, respectively. Variation of HRT also affected microbial growth and activity. Decreasing HRT from 25 to 8 and 4 h resulted in enhancement of microbial growth on carriers from 11.23 to 14.07 and 16.43 mg/g as well as SOUR from 8.01 to 14.66 and 22.53 mg O₂/g MLVSS.h, respectively. This means HRT of 4 h was the favourable condition for the lab scale MBBR.
In conclusion, the results indicate that MBBR with polyethylene media as biofilm carrier possessed great potential to be used for OMs removal from water and wastewater.