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In this study a novel activated carbon derived from Raffia palm shells was synthesized firstly by activating the precursor with phosphoric acid to produce Raffia Palm Shell Activated Carbon (RPSAC) and further functionalized by coating its surface with aluminium hydroxide to produce a composite called Aluminium Oxide-coated Raffia Palm Shell Activated Carbon (ACRPSAC). These adsorbents were extensively characterized and tested for fluoride adsorption in aqueous media using batch adsorption experiment in comparison with a commercially available activated carbon (CAC). ACRPSAC demonstrated excellent qualities and fluoride adsorption capacity as compared to RPSAC. SEM/EDX revealed that ACRPSAC developed both micro and meso-pores on its surface with BET-surface area and pore volume of 715.80 m2/g and 0.47 cm3/g respectively. FTIR and XRD proved that ACRPSAC was largely amorphous and had sufficient functionality for fluoride uptake in solution. Batch adsorption studies showed that the fluoride removal abilities were in the order of ACRPSAC > RPSAC > CAC with maximum Langmuir adsorption capacity of 4.10 > 2.26 > 2.24 mg/g. respectively. The experimental data was well described by the Langmuir (R2 = 0.8802–0.9751) and the pseudo-second order kinetic (R2 = 0.9974–0.9999) models, signifying that fluoride uptake by the adsorbents was a chemisorption process. Thermodynamic studies revealed that the process was spontaneous, endothermic and feasible for ACRPSAC and RPSAC but was non-spontaneous for CAC. It was concluded that ACRPSAC is an excellent activated carbon for eliminating fluoride from groundwater and can be further studied for its commercialization.

Aerobic granular sludge membrane bioreactor (AGMBR) has emerged with strong potential to overcome membrane fouling. There have been no extensive studies on extracellular polymeric substances (EPS) in AGMBR. The present work aimed at conducting an in-depth study of EPS and monitoring fouling development in AGMBR using a 22 factorial design having hydraulic retention time (HRT) and total organic carbon (TOC) as independent variables. HRT was tested at three levels of 6, 8 and 10 h while the TOC levels were 104 ± 13, 189 ± 17, and 266 ± 27 mg/L. AGMBR exhibited high proteins (PN) in the tightly-bound EPS (TB-EPS) resulting in high proteins/polysaccharides (PN/PS) ratios of 2–16. The PN in the LB-EPS was low, ranging from 0.01 to 1.92 mg/g MLVSS, but the range of PN/PS ratio was also of 2–16. Despite the high PN/PS ratio, TMP rise was low. Water jet easily sloughed off the developed membrane cake layer. The elimination of chemicals for membrane cleaning has significant cost savings. TOC had a significant main effect on both the PN and PS components of TB-EPS at α

The capability of submerged aerobic granular sludge membrane bioreactor (AGMBR) to remove organics and nutrients was studied in a 2 × 2 factorial experimental design. The hydraulic retention time (HRT) - 6, 8 and 10 h - and chemical oxygen demand (COD) - 298 ± 32, 543 ± 14, and 790 ± 33 mg/L - were the independent variables. AGMBR achieved >96%, 97%, 50%, and 35% removal for COD, NH3-N, total nitrogen, and PO4-P, respectively. Meganema and Thauera, responsible for organics degradation, were present during all the runs. Nitrosomonas and Nitrospira allowed for complete nitrification. The presence of Azoarcus and Thauera points to anoxic conditions in the granules, indicating partial denitrification. Negligible PAOs were detected; hence, low PO4-P removal (~35%) mainly via the consumption and biologically induced precipitation pathways. Overall, two runs - 298 ± 32 mg/L COD at 6 h HRT and 790 ± 33 mg/L COD at 6 h HRT - performed best in terms of organics and nutrients removal.

Aerobic granular sludge (AGS) offers the potential to degrade tannin/lignin found in pulp and paper wastewater (PPW). In this study, aerobic granules were cultivated in a sequencing batch reactor (SBR) with tannin/lignin present in the range of 50–200 mg/L. The mature granules were transferred to a real PPW wastewater system containing tannin/lignin concentration up to 500 mg/L. Biodegradation and biosorption were observed to be the two pathways for the removal tannin/lignin. Biosorption was a primary form of removal at lower concentrations, achieving 74% removal at 50 mg/L. The biosorption ability reduced to 58% removal at 200 mg/L. This reveals that biodegradation prevails at these higher concentrations. The Haldane kinetic parameters were: Vmax = 0.93 (g tannin/lignin/g VSS·day), Ks = 1910 mg/L, and Ki = 27 mg/L. Various adsorption kinetic models and isotherms were fitted to the system. The Langmuir isotherm coefficients were: (x/m) max = 21.5 (mg tannin/lignin/g SS), b = 0.00386 L/mg. The Freundlich isotherm had coefficients of n = 1.172, K = 0.1174. The study also delves into applying the technology towards real wastewater, achieving a COD removal of 79% and a tannin/lignin removal of 56%. Furthermore, experimental runs in warmer and more humid temperature conditions revealed higher removal efficiencies, achieving about 80% tannin/lignin degradation at a concentration of 130 mg/L. Results from this study will help ascertain an appropriate design protocol for full-scale industrial applications.

The present study attempted to optimize the nutrients required for biological growth and biomass synthesis in the treatment of high-strength organics wastewater using aerobic granular sludge (AGS). Three identical sequencing batch reactors (SBRs) were used to cultivate aerobic granules at COD concentration of ~5000 mg/L at COD:N:P ratios of 100:2.8:0.4, 100:4.4:0.5, and 100:5:0.7. Results indicated that the amount of nutrients needed for biomass growth does not follow the conventional organics to nutrients ratio (COD:N:P) of 100:5:1 when dealing with high-strength organics wastewater. The highest removal efficiency was achieved at COD:N:P ratio of 100:2.8:0.4, where COD, TN, and P removal was 98.8 ± 0.3%, 100.0 ± 0.0%, and 99.3 ± 1.0%, respectively. Moreover, the presence of high amounts of organics led to the dominance of the fast-growing heterotrophs in all SBRs, with the genus Thauera identified as the most abundant genera (23-40%), while autotrophic nitrifiers disappeared. The observed biomass yield at COD:N ratio of 100:2.8 suggested that heterotrophic nitrification may have occurred, while at COD:N ratios of 100:4.4 and 100:5, all the nitrogen was used for biomass synthesis. Moreover, at COD:N ratio of 100:5, almost 1/5 of the organics were utilized by the biomass cells to produce EPS as defensive action against the effects of free ammonia. Batch optimization experiments showed that the fastest rate of removal occurred at COD:N:P ratio of 100:1.1:0.4. After 4 h, the COD, TN, and P removal efficiencies were 95%, 99%, and 96%, achieving overall removal efficiencies of 98%, 100%, and 97% respectively, at HRT of 8 h. The bacterial behavior in consuming the organics was altered under nutrient-deficient conditions, where faster degradation rates were observed as the amounts of nutrients decreased, with higher relative abundance of heterotrophs and diazotrophic bacterial populations.

Tannin and lignin from pulp and paper wastewater (PPW) are two compounds that have been proven to cause a variety of toxic effects in several aquatic species. Aerobic granular sludge (AGS) technology has emerged with strong potential to provide the desired treatment. This work presents the first attempt at the microbial degradation of these compounds using AGS technology, with promising results. Granules were cultivated within 9 days of operation of the sequencing batch reactor (SBR), with SVI30 of 51.6 mL/g, achieving steady-state within the first three weeks of operation. On average, COD removal efficiency was 90%. Granules cultivated from the SBR were transferred into a batch system with real pulp mill effluent. Tannin/lignin removal efficiency was 97% at an initial concentration of 50 mg/L, and slowly decreased to about 60% when the influent concentration increased to 100 mg/L. The most prominent species responsible for the degradation of these toxic substances were Pseudomonas, Corynebacteriaceae and Flavobacterium. These key findings demonstrate the capability of AGS to provide adequate treatment for PPW.

Aerobic granulation is a complex process that, while proven to be more effective than conventional treatment methods, has been a challenge to control and maintain stable operation. This work presents a static data-driven model to predict the key performance indicators of the aerobic granulation process. The first sub-model receives influent characteristics and granular sludge properties. These predicted parameters then become the input for the second sub-model, predicting the effluent characteristics. The model was developed with a dataset of 2600 observations and evaluated with an unseen dataset of 286 observations. The prediction R2 and RMSE were >99% and

This work investigated the long-term stability of aerobic granular sludge treating high-strength organic wastewater in a semi-pilot scale sequential batch reactor (SBR). The reactor was operated for 316 days under different operational conditions. It was found that the F/M ratio is an important parameter affecting granules formation and stability. Three selection mechanisms were investigated: (1) cultivation and maturation at moderately high influent COD concentration (2500 mg/L) followed by increase in influent COD concentration to 7500 mg/L; (2) stressed cultivation and operation at high influent COD concentration of 4500 mg/L; and (3) alternate feed loading strategy (variable influent COD concentration across the daily schedule of cycles at 50%, 75%, and 100% of the peak concentration of 5000 mg/L). It was found that adopting high OLR at the reactor start-up accelerated the formation of granules. However, the overgrowth of biomass under high organics concentration negatively affected the stability of granules and led to disintegration due to the presence of methanogens in the granule core. Cultivation at high organics concentration resulted in a rapid loss of microbial diversity and reactor failure. Under alternate feed loading, adequate selection of microbial community was maintained and resulted in stable reactor performance. Moreover, a strong correlation between F/M ratio and the granules settling ability was observed. When F/M ratio exceeded 1.5 gCOD/gSS.d, granules showed poor settleability and under very high sludge loading rates (above 2.5), sludge bulking occurred and led to washout of sludge due to the strong selection pressure of short settling time. Operating the reactor at F/M ratio of 0.5–1.4 gCOD/gSS.d appears to favor stable long-term granule stability.

Process-affected water from the Canadian oil sands industry contains long chain cycloalkane carboxylic acids called naphthenic acids (NAs). The present proof-of-concept study aimed at assessing the shock response and treatability of commercial NAs using aerobic granular sludge (AGS) over 21 days. Mature aerobic granules were cultivated in a 5 L sequencing batch reactor (SBR) using synthetic acetate-based wastewater, and subjected to the NA mixture in three stages with varying organic loading rates. The introduction, starvation and the monitoring phases each had COD (chemical oxygen demand) removal efficiencies of 54.8%, 23.9% and 96.1%, and NA removal efficiencies of 71.8%, 43.3% and 67.0%, respectively. AGS biomass concentrations requiring higher COD consumption, and AGS surface area facilitating biodegradation and biosorption produced high specific removal rates. Specific COD removal rates ranged between 2678 and 6864 g COD/m3/d, whereas specific NA removal rates ranged between 0.5 and 12.2 g NA/m3/d. Supplemental nutrients were also degraded with over 90% removal efficiencies.

This work presents the first attempt in the treatment of high-strength organic wastewater at organic loading rate (OLR) up to 30 kg/m3 d in an aerobic granular sludge sequencing batch reactor. The reactor was operated for 100 days, divided into two main periods according to the applied OLR. In the first period, aerobic granules were cultivated and allowed to stabilize at an OLR of 10.2 ± 2.1 kg COD/m3 d (from the reactor start-up until day 41). In the second period (from day 42 to day 100), the applied OLR was 27.0 ± 3.5 kg COD/m3 d. Stable aerobic granules of average diameter of 1–2 mm dominated the reactor after 30 days, improving the settleability of the biomass. The COD removal efficiency was 98.4 ± 1.1% during the first 45 days of operation. However, after increasing the OLR, the COD removal efficiency decreased drastically to 64.4 ± 13.7% from days 46 to 64. Thereafter, the reactor recovered from the shock load and the removal efficiency increased to 96 ± 2.7% until the end of the 100 days. The effect of COD/N ratio was investigated for the treatment of nitrogen-deficient wastewater. It was shown that under severe nitrogen-deficient conditions (COD/N ratio > 70), the COD removal efficiency was 64.4 ± 13.7%. A COD/N ratio of 25–30 should be attained to ensure that there is no limitation in heterotrophic growth. The results from this study indicate that aerobic granulation can provide a promising high-strength organic wastewater treatment technology.

Membrane fouling mitigation has been variously reported in aerobic granular sludge membrane bioreactor (AGMBR). AGMBR has also achieved, to varying degrees, the removal of organics and nitrogen-based compounds from wastewater. However, scanty information is available in the literature on phosphorus removal in AGMBR. Thus, the present study focused on simultaneous removal of organics and both nutrients (nitrogen and phosphorus) in AGMBR at semi-pilot-scale. Aerobic granules were cultivated in a cylindrical reactor with a working volume of 19 L, diameter of 15 cm, and height-to-diameter (H/D) ratio of 8. The effluent from the granular reactor was discharged into a side-stream membrane module. At steady state, the granule mean size, 5-min sludge volume index (SVI5), SVI30, and MLSS were 576 μm, 40 mL/g, 37 mL/g, and 9200 mg/L, respectively. Results show that the system achieved 98% chemical oxygen demand (COD) degradation, 96–99% total nitrogen (TN) removal, and ≥95% removal of PO4-P. The outstanding removal of both organics and nutrients in the AGMBR is attributed to the coexistence of aerobic and anaerobic layers within the granule as well as the anaerobic feeding adopted. These findings demonstrate the potential of AGMBR to simultaneously remove organics and nutrients (nitrogen and phosphate)

The wood pulping process and the production of paper products generate wastewater with a variety of toxic pollutants in high concentrations. Pulp and paper wastewater (PPW) contains complex organic and inorganic pollutants depending on the type of pulping process. This paper provides an overview of biological treatment of PPW. Conventional biological processes such as activated sludge struggle to treat PPW to the required standard. Over recent years, a push towards more innovative solutions such as membrane bioreactors (MBR), sequential batch reactors (SBR), aerated lagoons and anaerobic filters have been suggested for the treatment of PPW. However, these technologies present several operational issues. A novel biotechnology, aerobic granular sludge (AGS), has emerged with strong potential to provide the desired treatment. Compared to activated sludge, granular sludge provides smaller footprints, better settleability, higher biomass retention, tolerance to toxicity, and resistance to shock loading, which are vital to PPW treatment. Early results on the application of AGS technology for PPW indicate very promising removal. However, pilot-scale testing is required to establish optimal operational conditions.

Machine learning models provide an adaptive tool to predict the performance of treatment reactors under varying operational and influent conditions. Aerobic granular sludge (AGS) is still an emerging technology and does not have a long history of full-scale application. There is, therefore, a scarcity of long-term data in this field, which impacted the development of data-driven models. In this study, a machine learning model was developed for simulating the AGS process using 475 days of data collected from three lab-based reactors. Inputs were selected based on RReliefF ranking after multicollinearity reduction. A five-stage model structure was adopted in which each parameter was predicted using separate models for the preceding parameters as inputs. An ensemble of artificial neural networks, support vector regression and adaptive neuro-fuzzy inference systems was used to improve the models’ performance. The developed model was able to predict the MLSS, MLVSS, SVI5, SVI30, granule size, and effluent COD, NH4-N, and PO43− with average R2, nRMSE and sMAPE of 95.7%, 0.032 and 3.7% respectively.

Aerobic granular sludge (AGS) has emerged as a novel biotechnology for the effective treatment of both municipal and industrial wastewater. Two of the practical parameters that affect aerobic granule (AG) formation and stability are the feeding strategy and organic loading rate (OLR). In this paper, the impact of feeding strategy and OLR on AG formation and stability are reviewed. The feeding strategy that appears suitable for stable AG formation using all substrates is slow anaerobic feeding. Despite the long duration for AG cultivation at low OLR, compact and stable AG are formed. High OLRs result in fast AG formation but the developed granules are unstable due to the large size resulting from excessive microbial growth. The recommended strategy for stable AG formation with enhanced treatment performance is stressed (high) OLR for fast granule formation followed by reduced OLR to ensure stability. This can be combined with slow anaerobic feeding to select for slow-growing microorganisms and nutrients removers such as phosphate-accumulating organisms (PAOs). Further research is recommended to explore AG formation at high OLR using the slow anaerobic feeding strategy for long-term stability.

This study aimed at determining the treatability of high-strength wastewater (chemical oxygen demand, COD>4000 mg/L) using combined anaerobic-aerobic granular sludge in lagoon systems. The lagoon systems were simulated in laboratory-scale aerated and non-aerated batch processes inoculated with dried granular microorganisms at a dose of 0.4 g/L. In the anaerobic batch, a removal efficiency of 25% was not attained until the 12th day. It took 14 days of aerobic operation to achieve sCOD removal efficiency of 94% at COD:N:P of 100:4:1. The best removal efficiency of sCOD (96%) was achieved in the sequential anaerobic-aerobic batch of 12 days and 2 days, respectively at COD:N:P ratio of 200:4:1. Sequential anaerobic-aerobic treatment can achieve efficient and cost effective treatment for high-strength wastewater in lagoon systems.

The elevated organic content of high-strength wastewater makes aerobic treatment systems uneconomical. High-strength wastewaters are preferably treated anaerobically, thus providing a potential for energy generation while producing low surplus sludge. This paper provides an overview of high rate anaerobic digesters developed during the second half of the last century, focusing on anaerobic filter (AF), anaerobic fluidized-bed reactor (AFBR), and upflow anaerobic sludge blanket (UASB), along with their applications in high-strength wastewater treatment. Despite the unique compact design of these systems that combines the treatment and clarification in one reactor, they fail to provide complete stabilization of high-strength wastewater. Further downstream treatment is usually required to meet effluent regulatory limits. Therefore, advanced hybrid systems such as membrane bioreactors (MBRs), combined and integrated anaerobic–aerobic bioreactors are discussed in this review for their potential as effective treatment alternatives. The factors affecting the performance of these hybrid systems have been highlighted. MBRs provide excellent effluent quality with reduced footprint, but their major drawback is membrane fouling which increases maintenance and operating costs. Combined anaerobic and aerobic systems have been developed to provide a cost effective and efficient treatment for high-strength wastewater. Integrated anaerobic–aerobic systems employing biogranulation can provide a promising high-strength wastewater treatment technology. However, the design and operation of the integrated granular bioreactors are still in the development phase with limited data in continuous flow regime and large-scale operation. Long-term granule stability and long start-up are other obstacles. Further research is needed to overcome these shortcomings.

Maintaining stable operation of aerobic granular sludge (AGS) reactors is a challenge due to the high sensitivity of the biomass to a wide array of parameters, and the frequent changes in influent characteristics. The application of artificial intelligence in AGS modelling has shown promising results but is still at its early stages. This work investigated, for the first time, the capabilities of two artificial intelligence algorithms for the development of predictive models for AGS reactors based on influent characteristics and operational conditions: adaptive neuro-fuzzy inference system (ANFIS), and support vector regression (SVR). The model structure adopted a two-stage modular approach. The models predicted the performance of the reactors for the unseen data with an average R2, nRMSE, sMAPE, and MASE of 91 %, 0.21, 0.06, and 0.22 for ANFIS, and 99 %, 0.07, 0.006, and 0.01 for SVR. The results showed that SVR provides more accurate predictions than ANFIS, in terms of prediction errors, and correctly predicting different types of failures. However, ANFIS provided better generalization ability than SVR. The results of this study showed the potential of artificial intelligence for the development of predictive models for the AGS process and provided insight into the selection of the appropriate algorithms for these models.

The deterioration of the structural integrity of aerobic granular sludge (AGS) in long-term operation is a major limitation of the AGS biotechnology. The present study explored AGS long-term stability at semi-pilot-scale using the combined strategy of long anaerobic slow feeding, 1:3 fixed ratio of feast-famine period within each cycle, and selective discharge of mature granules. Biomass characteristics, extracellular polymeric substances (EPS), dissolved oxygen and removal profiles were monitored. Results indicate that the 1:3 ratio of feast-famine period controlled the EPS content at a suitable level to allow for granular sludge stability. The system exhibited high proteins (PN) content of EPS, resulting in high PN/polysaccharides (PS) ratios: 0.01–19 and 2.05–13.15 for loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS), respectively. Selective withdrawal of mature granules from the bottom of the reactor resulted in a good mix of new and old granules in the system. The strategy allowed for system stability as the reactor was operated for over 240 d without any granule disintegration. High removals of COD (98.3 ± 0.8 %), NH3-N (98.5 %), and TN (89±6 %) were achieved. Phosphate-P removal was in the range 50–100 %. EPS producers (Thauera, Flavobacterium and Meganema) and slow growing bacteria (Acinetobacter and Simplicispira) in the system contributed to the AG stability.

Aerobic granular sludge (AGS) has previously been utilized in the treatment of toxic compounds due to its diverse and dense microbial structure. The present study subjected mature AGS to model naphthenic acids (NAs) representative of the Canadian oil sands. To this effect, three NA concentrations (10, 50 and 100 mg/L) and three supplemental carbon source concentrations (600, 1200 and 2500 mg/L) were studied in batch reactors for 5 days. The responding variables were chemical oxygen demand (COD), NA concentrations and nutrients. Cyclohexane carboxylic acid (CHCA), cyclohexane acetic acid (CHAA) and 1-adamantane carboxylic acid (ACA) were chosen to study structure-based degradation kinetics. The optimal COD according to the runs was 1200 mg/L. CHCA was removed completely with biodegradation rate constants increasing with lower NA concentrations and lower COD concentrations. CHAA was also removed completely, however, an optimal rate constant of 1.9 d−1 was achieved at NA and COD concentrations of 50 mg/L and 1200 mg/L, respectively. ACA removal trends did not follow statistically significant regressions; however, degradation and sorption helped remove ACA up to 19.9%. Pseudomonas, Acinetobacter, Hyphomonas and Brevundimonas spp. increased over time, indicating increased AGS adaptability to NAs.

The discharge of untreated high-strength wastewater into water bodies results in water quality deterioration of the receiving waters. The aim of this study was to assess the impact of abattoir wastewater discharge on the water quality of river Kaduna, Nigeria. Water samples were collected from river Kaduna at three points: 100m upstream of the abattoir discharge point, at the discharge point, and 100m downstream of the discharge point for a 6-month period (July- September in the rainy season and October-December in the dry season). Physico-chemical analyses were conducted on the collected samples in the laboratory using standard methods. The pH was within a fixed band of 6-8. The downstream 5-day biochemical oxygen demand of the receiving river water increased significantly to 75% in July and up to 192% in December. Suspended solids, chemical oxygen demand, ammonia-nitrogen, total nitrogen and total phosphorus followed a similar trend. Dissolved solids, dissolved oxygen, nitrate-N, iron, zinc and cadmium also increased appreciably. The downstream levels of these parameters were higher than their corresponding upstream values, indicating that the discharge of the abattoir wastewater into the river has negatively impacted the river water. The dilution of the waste in the river water was not enough to reduce them to acceptable levels. This research demonstrates that abattoir wastewater impacts the river water negatively. The findings can be useful in identifying water quality problem areas and planning of engineering interventions as well as basis for legislation.

Groundwater is the main source of water for most city dwellers in Nigeria. In this study, the impacts of urban livestock production on groundwater quality in Kaduna metropolis were assessed through water quality monitoring. Groundwater samples were collected from wells located around 2 abattoirs (Tudunwada and Kawo abattoirs) and in 8 livestock-keeping households for a 6-month period (July- December). Physico-chemical analyses were conducted on the samples using standard methods. Results indicate that groundwater is negatively impacted in terms of 5-day biochemical oxygen demand, chemical oxygen demand, nitrate-nitrogen, total phosphorus and cadmium; and this impact is of great concern as the values for these parameters are well in excess of established limits. There is negative impact in terms of pH, electrical conductivity, total dissolved solids and zinc but this impact is not a concern as most of the values are within limits. However, no impact was observed on groundwater quality in terms of calcium as it showed no definite pattern of variation. Similarly, iron exhibited very low concentrations in the samples with a few exceptions in the months of July and August for the two abattoir sites. Lead was not detected in any of the samples throughout the study period. This study indicates that livestock keeping and processing activities have negative impact on groundwater quality in Kaduna metropolis. The groundwater pollution due to urban livestock production emanates from point sources and control measures can be easily applied.

The study explored the production of biogas from Lemon grass, Cow dung and Poultry droppings. The three substrates were pre-fermented according to standard methods. Six (6) kg of each pre-fermented substrate was mixed with water in ratio 1:1 v/v to form slurry and digested for 30days. A total of 0.125m(3), 0.191m(3) and 0.211m(3) of biogas were respectively produced from the Lemon grass, Cow dung and Poultry droppings with deviations of 0.00234m(3), 0.00289 m(3) and 0.00484 m(3) respectively. The cooking test carried out revealed that the scrubbed gas had higher cooking rates for water (0.12L/min, 0.085L/min and 0.079L/min for Lemon grass, Cow dung and Poultry droppings respectively) while the cooking rates for unscrubbed gas were 0.079L/min, 0.064L/min and 0.06L/min respectively. The pH of the medium fluctuated optimally between 6.5 and 7.8. The research demonstrated that Lemon grass produced less volume but better quality biogas compared to Cow dung and Poultry droppings.

Membrane fouling is considered the major limitation of membrane bioreactors (MBRs). This paper provides an overview on fouling mitigation in MBRs using granular materials. Adsorbents addition extends filtration period, improves critical flux as well as sludge properties (increased flocs size, reduced soluble EPS, improved dewaterability). However, determination of optimal dosages of adsorbents is needed to balance cost savings from fouling mitigation versus cost of adsorbents and sludge handling. The abrasion from granular media reduces cake layer formation, extends membrane filtration period, increases flux (∼20-30%), and reduces aeration intensity by 50%. Finding appropriate aeration intensity and optimum dose for different media is critical for full-scale application. Granular sludge substantially reduces fouling in MBRs; but, optimal operational conditions for long-term granule stability are required. Quorum quenching (QQ) mitigates biofouling (energy savings ∼27-40%). Cost savings from QQ need assessment against the production and application of QQ approaches.