Development of a dynamic model for effective mitigation of membrane fouling through biogas sparging in submerged anaerobic membrane bioreactors (SAnMBRs).

The deterministic mechanistic model derived from the fundamental of the dynamical fouling system was investigated to estimate fouling parameters, with theoretical biogas sparging performance evaluated of a Submerged Anaerobic Membrane Bioreactor treating trade wastewater. The result showed that the sparging effectiveness of EPSc removal was average, 35% higher than the sparging effectiveness of EPSp, with the coefficient of fouling removal characterizing the dynamic time behaviour increasing with the organic loading rate. The dynamic system analysis predicted that the process gain for SAnMBR-1 was more than 30% compared with SAnMBR-2, which supported a widely known theory of fouling dependence of organic loading rate.

Technical advances on current research trends and explore the future scope on nutrient recovery from waste-streams: a review and bibliometric analysis from 2000 to 2020.

An exponentially growing global population has led to an increase in nutrient pollution in different aqueous bodies. Although different processes have successfully removed nutrients from wastewater on a large scale, a limited number of studies have been reported on efficiency, cost-effectiveness, and future potential of physical, chemical, and biological nutrient recovery methods to overcome the depletion of natural resources. Therefore, researchers need to understand current research trends by applying different approaches to investigate higher efficient nutrient recovery technologies. In this article, the research patterns and in-depth review of various nutrient recovery processes have been circumscribed with the application of bibliometric and attractive index (AAI) vs. activity index (AI) analysis. The performance, advantages, limitations, and future prospects of different nutrient recovery methods have also been addressed. More than 70% of study publications were published in the last decade in chemical and biological processes, which might be related to more rigorous effluent quality rules and increasing water pollution. The future prediction in the field of nutrient recovery has been predicted using S-curve analysis, and it was found that the number of publications in the saturated state in chemical methods was highest. However, the growth rate of the biological-based nutrient recovery methods is greater, which may be because of their huge research scope, cost-effectiveness, and easy operation methods. This study can assist researchers in understanding the current research scenario in nutrient recovery techniques and provide the research scope in nutrient recovery from wastewater in the future.

Evaluation of membrane cake fouling mechanism to estimate design parameters of a submerged AnMBR treating high strength industrial wastewater.

A mathematical model, which was previously developed for submerged aerobic membrane bioreactors, was successfully applied to elucidate the membrane cake-layer fouling mechanisms due to bound extracellular polymeric substances (eEPS) in a submerged anaerobic membrane bioreactor (SAnMBR). This biofouling dynamic model explains the mechanisms such as attachment, consolidation and detachment of eEPS produced in the bioreactor on the membrane surface. The 4th order Runge-Kutta method was used to solve the model equations, and the parameters were estimated from simulated and experimental results. The key design parameters representing the behaviour of cake fouling dynamics were systematically investigated. Organic loading rate (OLR) was considered a controlling factor governing the mixed liquor suspended solids (MLSS), eEPS production, filtration resistance (Rt), and transmembrane pressure (TMP) variations in a SAnMBR. eEPS showed a proportional relation with OLR at subsequent MLSS variations. The consolidation of EPS increased the specific eEPS resistance (αs), influencing the cake resistance (Rc). The propensities of eEPS showed a positive correlation with Rt and TMP. The outcomes of the study also estimated a set of valuable design parameters which would be vital for applying in AnMBRs treating industrial wastewater.

The potential of adopting struvite precipitation as a strategy for the removal of nutrients from pre-AnMBR treated abattoir wastewater.

Large volume of wastewater consisting complex forms of organics, lipids and nutrients, is discharged from the abattoir (red meat) processing industry. In this study, nutrient rich pre-Anaerobic Membrane Bioreactor (AnMBR) treated abattoir effluent was fed to a struvite (MgNH4PO4.6H2O) precipitator to evaluate the possibility of developing an innovative environmentally sustainable treatment technology to produce nutrient free high-quality treated effluent. A series of continuous and batch experiments were conducted to investigate the influence of pH and presence of Ca2+ on struvite precipitation. The study found that Mg2+:Ca2+ molar ratio of 0.8 (or high Ca2+) impacts on the production and quality of struvite significantly. Pre-AnMBR treated abattoir wastewater with negligible Ca2+ (Mg2+:Ca2+ molar ratio > 20) showed over 80% removal of phosphorus via struvite precipitation. The highest removal rates of both nitrogen and phosphorus were achieved at pH 9.5 with Mg2+:PO43- molar ratio of 2:1.

Proof of Concept for Light Conducting Membrane Substrate for UV-Activated Photocatalysis as an Alternative to Chemical Cleaning.

Adopting an effective strategy to control fouling is a necessary requirement for all membrane processes used in the water/wastewater treatment industry to operate sustainably. The use of ultraviolet (UV) activated photocatalysis has been shown to be effective in mitigating ceramic membrane fouling by natural organic matter. The widely used configuration in which light is directed through the polluted water to the membrane's active layer suffers from inefficiencies brought about by light absorption by the pollutants and light shielding by the cake layer. To address these limitations, directing light through the substrate, instead of through polluted water, was studied. A UV conducting membrane was prepared by dip coating TiO2 onto a sintered glass substrate. The substrate could successfully conduct UV from a lamp source, unlike a typical alumina substrate. The prepared membrane was applied in the filtration of a humic acid solution as a model compound to study natural organic matter membrane fouling. Directing UV through the substrate showed only a 1 percentage point decline in the effectiveness of the cleaning method over two cleaning events from 72% to 71%, while directing UV over the photocatalytic layer had a 9 percentage point decline from 84% to 75%. Adapting the UV-through-substrate configuration could be more useful in maintaining membrane functionality during humic acid filtration than the current method being used.

Preparation, characterisation and critical flux determination of graphene oxide blended polysulfone (PSf) membranes in an MBR system.

Microfiltration membranes having different blends of graphene-oxide (GO) (0-1 wt%) and Polysulfone (PSf) (15-20 wt%) were prepared using the classical non-solvent induced phase inversion process. The prepared membranes were characterised for their structural morphology, surface properties, mechanical strength, porosity and pure water flux. Based on the initial characterisation results, four membranes (15 wt% PSf, 15 wt% PSf + 0.25 wt% GO, 15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) were chosen for critical flux study, that was conducted using flux-step method in a lab scale MBR system. In order to study the application potential of GO blended membranes, the critical flux of each membrane was evaluated in two operational modes i.e., continuous and intermittent modes with backwash. The membranes with maximal GO concentration (15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) showed higher critical flux (16.5, 12.8 L/m2h and 19, 15 L/m2h for continuous and intermittent mode, respectively). It was observed that the operational modes did not have a significant effect on the critical flux of the membranes with low GO concentration (15 wt% PSf and 15 wt% PSf + 0.25 wt% GO), indicating a minimal of 1 wt% GO was required for an observable effect that favoured intermittent mode of operation. Through these results, ideal operating condition was arrived (i.e., flux maintained at 6.4 L/m2h operated under intermittent mode) and the membranes 15 wt% PSf and 15 wt% PSf + 1 wt% GO were studied for their long-term operation. The positive effect of GO on filtration time, cleaning frequency and against fouling was demonstrated through long term TMP profile of the membranes, indicating the suitability of GO blended membrane for real time wastewater treatment.

Treatment of textile wastewater with membrane bioreactor: A critical review.

Membrane bioreactor (MBR) technology has been used widely for various industrial wastewater treatments due to its distinct advantages over conventional bioreactors. Treatment of textile wastewater using MBR has been investigated as a simple, reliable and cost-effective process with a significant removal of contaminants. However, a major drawback in the operation of MBR is membrane fouling, which leads to the decline in permeate flux and therefore requires membrane cleaning. This eventually decreases the lifespan of the membrane. In this paper, the application of aerobic and anaerobic MBR for textile wastewater treatment as well as fouling and control of fouling in MBR processes have been reviewed. It has been found that long sludge retention time increases the degradation of pollutants by allowing slow growing microorganisms to establish but also contributes to membrane fouling. Further research aspects of MBR for textile wastewater treatment are also considered for sustainable operations of the process.

Evaluation of herbicide (persistent pollutant) removal mechanisms through hybrid membrane bioreactors.

A laboratory-scale membrane bioreactor (MBR) combined with ultraviolet (UV) disinfection and granular activated carbon (GAC) adsorption was researched for over seven months to evaluate the removal efficiencies and mechanisms of a moderately persistent s-triazine herbicide (Ametryn), which is commonly used in Australian sugarcane farmlands. Long-term experiments showed that MBR alone (15h hydraulic retention time (HRT)) can remove 65% of Ametryn from its influent which had a concentration of 1-2mg/L. A batch study was carried out to assess the mechanisms of removal of Ametryn through MBR and found that 0.1186mg of Ametryn/g-VSS is adsorbed onto sludge particles when 1mg/L of Ametryn is added to the mixed liquor and showed a 64% removal after 12h. This experiment confirmed that 99%, 92% and 83% removal of Ametryn could be achieved only from biodegradation, if the MBR maintains a HRT of 7.5, 2.5 and 1.5days respectively.

Performance of a laboratory-scale membrane bioreactor consisting mixed liquor with aquatic worms under toxic conditions.

A laboratory scale membrane bioreactor (MBR) consisting of worms was operated for 214days. The objective was to evaluate the treatment and operating performance of the MBR with and without the addition of Ametryn which is a toxic and persistent herbicide. Removal of Ametryn was doubled (up to 80%) in the MBR when the worms were present. Increased rate (2.5kPa/day) of trans-membrane pressure (TMP) and low concentration of MLSS (5.5g/L) were recorded when the worm population was high (80-100 worms per 70µL). Short-term critical flux values were increased from 7.5 to 15 and then to 30L/m(2)/h when the worm numbers decreased from 90 to 35 and then to 18 per 70µL of mixed liquor respectively. Further, high levels of carbohydrate concentration of soluble microbial products (SMP) and smaller sludge floc-sizes were found when the worm numbers were high.

Impact of herbicide Ametryn on microbial communities in mixed liquor of a membrane bioreactor (MBR).

Ametryn, which is a second generation herbicide, was introduced to a lab-scale MBR at a concentration of 1mg/L and a 20-40% removal was observed at HRT ranging from 7.8 to 15.6h for an average influent Ametryn concentration of 0.8 mg/L. Components of EPS (protein and carbohydrates) increased in the bioreactor and the observed biomass production reduced after the addition of Ametryn. In a batch study, GAC was added to MBR mixed liquor and removal of Ametryn via biodegradation and adsorption were measured. Five common bacterial colony types (Gram negative and positive bacilli and Gram negative cocci) were identified and three of these were resistant to Ametryn up to 5mg/L. GAC was found to be a very effective Ametryn adsorption medium and in some occasions Ametryn may have acted as a nutrient source for bacteria.

Model development and parameter estimation for a hybrid submerged membrane bioreactor treating Ametryn.

A lab-scale membrane bioreactor (MBR) was used to remove Ametryn from synthetic wastewater. It was found that concentrations of MLSS and extra-cellular polymeric substances (EPS) in MBR mixed liquor fluctuated (production and decay) differently for about 40 days (transition period) after the introduction of Ametryn. During the subsequent operations with higher organic loading rates, it was also found that a low net biomass yield (higher death rate) and a higher rate of fouling of membrane (a very high rate during the first 48 h) due to increased levels of bound EPS (eEPS) in MBR mixed liquor. A mathematical model was developed to estimate the kinetic parameters before and after the introduction of Ametryn. This model will be useful in simulating the performance of a MBR treating Ametryn in terms of flux, rate of fouling (in terms of transmembrane pressure and membrane resistance) as well as treatment efficiency.

Implications of short and long term critical flux experiments for laboratory-scale MBR operations.

This paper evaluates the critical flux obtained by different techniques including tests with different flux step lengths (20 and 40 min and 7 days) and modes of operation (continuous and intermittent) under low and high MLSS concentrations. The paper also analyses a couple of long-term tests (flow rate of 40 and 20 L/day) to obtain the time required to reach the critical flux experimentally and compares those values with the results obtained numerically from a mathematical model. It was found that intermittent mode with membrane relaxation was useful in controlling the fouling of membrane and in restoring the membrane from fouling at lower MLSS.