The main goal of the present study was to examine the operating characteristics and mechanisms of membrane fouling in integrated membrane bioreactors (IMBRs) at diff erent temperatures. Two IMBRs, each with identical dimensions and confi gurations, were used in the study using synthetic domestic sewage at a low temperature (10°C) and high temperature (25°C). The results indicated that the removal effi ciency of chemical oxygen demand reached 93–96%, but the membrane contribution rate of IMBR2 (10°C) was higher than that of IMBR1 (25°C). The separation burden of the membrane on organic compounds increased at low temperature, which may have sped up the rate of membrane biofouling. The absolute rate of trans-membrane pressure build-up was faster at low temperature, leading to shorter IMBR operating times. Soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) in the IMBRs signifi cantly increased at low temperature. These substances intensifi ed defl occulation, with an accompanying reduction of fl oc size and the release of EPSs at low temperature, which facilitated the formation of cake foulants on the surface, covering the entire membrane area. The protein and polysaccharide concentrations of SMPs and EPSs in the IMBRs were correlated with the concentration of C8-HSL. It was demonstrated that temperature aff ected the concentration of C8-HSL, which controlled the excretion of EPSs and SMPs and thus the membrane biofouling process.

Owing to its high concentrations of nitrogen and phosphorus, the slurry from water hyacinth (Pontederia crassipes) biogas production cannot be discharged directly without further treatment. To achieve the target of water recycling, a new strategy of combining a Carrousel oxidation ditch with a water spinach wetland was developed in this study for the harmless treatment of Pontederia crassipes biogas slurry. First, the water quality characteristics of the biogas slurry were measured. Then, comprehensive tests of the combined slurry treatment system were carried out to verify pollutant removal performance and mechanism. The results showed that the Carrousel oxidation ditch reduced the inlet pollutant load of the subsequent water spinach wetland. The chemical oxygen demand (COD), and ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) contents of the average effluent from the combined system were less than 50 mg/L, 1.6 mg/L, 6 mg/L, and 0.5 mg/L, respectively, which means that all met urban sewage treatment standard of Level 1 Grade A (GB18918-2002). Gas chromatography – mass spectrometry analysis showed that the combined system had decreased various types of organic pollutants in the biogas slurry exponentially, efficiently removing alkane pollutants, aromatic hydrocarbons, and heterocyclic compounds. Scanning electron microscopy images revealed very large surface area of the water spinach roots in the wetland, which played important roles in enriching the microorganisms and trapping organic matter. Plant absorption, microbial degradation, and filtration were the primary ways in which the water spinach wetland purified the biogas slurry.