Impact of poly dimethyldiallylammonium chloride on membrane fouling mitigation in a membrane bioreactor

Abstract

Poly dimethyldiallylammonium chloride (PDMDAAC) was applied in a membrane bioreactor (MBR) to study its effects on mitigation of MBR membrane fouling. Floc size, zeta potential, soluble microbial substances (SMP) and extracellular polymeric substances (EPS) secretion were studied with respect to PDMMAAC-dosing operations. Results demonstrated that a sustainable filtration cycle extended 3.3 times with the optimal PDMDAAC dosage of 90 mg L. The addition of PDMDAAC could increase zeta potential of sludge floc, which led to the decrease in repulsive electrostatic interactions between flocs, as well as the facilitation of flocs-to-flocs aggregation. With the optimal dosage of PDMDAAC, the mean size of sludge was 3.23 ± 0.55 times higher than the control group, resulting in higher impact resistance and better adaptive capacity to the changing environment, which led to less SMP secretion. Moreover, a high contaminants removal rate was achieved in the reactor that was dosed with PDMDAAC. The average effluent concentrations of chemical oxygen demand and total nitrogen were less than 45.6 ± 2.85 and 5.23 ± 0.61 mg L, respectively, and the corresponding removal rates were 93.1 ± 5.81% and 89.1 ± 9.61%.

Study of biogas slurry concentrated by reverse osmosis system: characteristics, optimization, and mechanism

“…Chemical treatment techniques are often used to reduce membrane fouling (Wang, Zhang, Li, & Hu, ; Zhou, Chen, et al., ; Zhou, Wu, et al., ); however, it often requires the addition of chemical reagents and may cause secondary pollution. Therefore, physical processing such as gravity settling and ultrafiltration process was acted as pretreatment for biogas slurry.…”

“…The reverse osmosis membrane has a requirement for the influent temperature, so in order to achieve a better treatment effect and protect the reverse osmosis membrane, the temperature needs to be controlled at specific temperature range in RO process (Zhou, Chen, et al., ; Zhou, Wu, et al., ). The effect of operating temperature on the removal rates of COD and NH 3 ‐N was investigated.…”

“…The interaction between membrane surface charge and organic acid of biogas slurry with the changing pH values might contribute to it (Fu, Ruiz, Thompson, & Spangenberg, ; Matsuura & Sourirajan, ). The raw biogas slurry is alkaline with pH above 8, since the concentration of volatile fatty acids (VFAs) is relatively low (≤0.24 g acetate/kg) after the anaerobic digestion (Bonmatı́ & Flotats, ; Zhou, Chen, et al., ; Zhou, Wu, et al., ). However, the humus presents abundant in the biogas slurry.…”

“…According to the acid–base equilibrium in biogas slurry, which is dominated by the “NH 3 –H 2 O–CO 2 ” system (Zhao et al., ), the free ammonia concentration is relatively high in the raw biogas slurry (Zhou, Chen, et al., ; Zhou, Wu, et al., ). In the test, the NH 3 ‐N removal rate decreased from 77.11% to 72.24% when influent pH increased from 6 to 9.…”

“…A few literatures revealed that membrane technology had great potentials for concentrating biogas slurry in terms of valorization. Some emerging membrane processes, such as hybrid membrane process (Ruan et al., ), disk tube‐reverse osmosis system (Gong et al., ; Zhou, Chen, et al., ; Zhou, Wu, et al., ), and cross‐flow ceramic membrane system (Zacharof & Lovitt, ), showed excellent nutrient recovery from biogas slurry. Besides, pH (Masse, Masse, & Pellerin, ) and membrane combination (Konieczny et al., ) could take effect on the characteristics of permeate.…”