Application of Moving Bed Biofilm Process for Biological Organics and Nutrients from Municipal Wastewater

Optimization of moving bed biofilm reactors for the treatment of municipal wastewater

The properties of biocarriers significantly influence the performance of a moving bed-biofilm reactor (MBBR). This study aimed to assess the impact of media type, filling ratio, and hydraulic retention time (HRT) on biofilm formation and MBBR performance in both batch and continuous setups using real municipal wastewater. Two different media, high-density polyethylene (HDPE) and polypropylene (PPE), with varying surface area and properties were used. Biofilm growth and MBBR performance were monitored and optimized using response surface methodology. The effect of different media was investigated for three filling ratios of 20%, 40% and 60% and HRT of 4, 6 and 8 h. Results depicted a better biofilm growth on HDPE media in comparison to PPE carriers due to difference in media structure and surface properties. At all the conditions tested, HDPE media showed comparatively better performance for the removal of organic matter and nutrients than PPE media. The maximum organic matter removal efficiency was found as 77% and 75% at an HRT of 6 h and filling ratio of 40% for HDPE and PPE media, respectively. The ammonia removal was also found better for HDPE media due to its geometry and structure favoring the anoxic conditions with maximum removal of 89% achieved at 6-h HRT and 40% filling ratio. Overall, the system with HDPE media indicated more stability in terms of reactor performance than PPE carriers with variations in the operating conditions.

Influence of salinity on biofilm formation and COD removal efficiency in anaerobic moving bed biofilm reactors

Anaerobic digestion is widely used for wastewater treatment, but this approach often relies on microbial communities that are adversely affected by high-salinity conditions. This study investigated the applicability of an anaerobic moving bed biofilm reactor (AMBBR) to treating high-salinity wastewater. The removal performance and microbial community were examined under salinity conditions of 1000-3000 mg/L, and a soluble chemical oxygen demand (sCOD) removal efficiency of up to 8% ± 2.74% was achieved at high-salinity. Scanning electron microscopy showed that microorganisms successfully attached onto the polyvinyl alcohol gel carrier, and the extracellular polymeric substances on the biofilm increased at higher salt concentrations. The AMBBR also maintained traditionally accepted levels of total alkalinity and volatile fatty acids for stable wastewater processing under these operating conditions. High-throughput sequencing indicated that Desulfomicrobium and three methanogenic groups were the dominant contributors to sCOD removal. Overall, the results showed that the AMBBR can successfully treat fish factory wastewater under varying salinity conditions.

A review of ammonia removal using a biofilm-based reactor and its challenges

Extensive growth of industries leads to uncontrolled ammonia releases to environment. This can result in significant degradation of the aquatic ecology as well as significant health concerns for humans. Knowing the mechanism of ammonia elimination is the simplest approach to comprehending it. Ammonia has been commonly converted to less hazardous substances either in the form of nitrate or nitrogen gas. Ammonia has been converted into nitrite by ammonia-oxidizing bacteria and further reduced to nitrate by nitrite-oxidizing bacteria in aerobic conditions. Denitrification takes place in an anoxic phase and nitrate is converted into nitrogen gas. It is challenging to remove ammonia by employing technologies that do not incur particularly high costs. Thus, this review paper is focused on biofilm reactors that utilize the nitrification process. Many research publications and patents on biofilm wastewater treatment have been published. However, only a tiny percentage of these projects are for full-scale applications, and the majority of the work was completed within the last few decades. The physicochemical approaches such as ammonia adsorption, coagulation-flocculation, and membrane separation, as well as conventional biological treatments including activated sludge, microalgae, and bacteria biofilm, are briefly addressed in this review paper. The effectiveness of biofilm reactors in removing ammonia was compared, and the microbes that effectively remove ammonia were thoroughly discussed. Overall, biofilm reactors can remove up to 99.7% ammonia from streams with a concentration in range of 16-900 mg/L. As many challenges were identified for ammonia removal using biofilm at a commercial scale, this study offers future perspectives on how to address the most pressing biofilm issues. This review may also improve our understanding of biofilm technologies for the removal of ammonia as well as polishing unit in wastewater treatment plants for the water reuse and recycling, supporting the circular economy concept.

The use of recycled materials in a biofilter to polish anammox wastewater treatment plant effluent

Anammox is gaining popularity for treating wastewater containing high-strength ammonia due to lower energy demand compared to conventional nitrification-denitrification processes; however, anammox is reported to increase nitrate loads in the effluent. The objective of this study was to assess the applicability of recycled materials [recycled concrete aggregate (RCA) and rice husks (RH)] as a polishing step to improve anammox reactor effluent quality. Anammox effluents were separately passed through two single-stage columns containing RCA and RH, and one two-stage column (50% RCA, 50% RH) to quantify total N, ammonia, nitrate, nitrite, and phosphate removal efficiencies. Langmuir isotherm experiments were conducted to quantify nitrate, nitrite, and phosphate sorption capacities in the columns. The RCA column exhibited the highest phosphate sorption capacity (0.074 mg/g), while the RH column exhibited higher nitrite and nitrate adsorption (0.063 mg/g and 0.023 mg/g respectively). We created a Hydrus-1D model to estimate pseudo-first-order reaction rates in the columns. Because RCA media can form metal-phosphate precipitates, the fastest phosphate reaction rate (1.58 min-1) occurred in the RCA column. The two-stage column demonstrated the greatest overall removals for all nutrients, and removal rates were consistent throughout the experimental period. The two-stage column achieved 15% total N, 94% ammonia-N, 38% nitrate-N, 75% nitrite-N, and 27% phosphate removal. The maximum nitrite, nitrate, and phosphate adsorption capacities in the two-stage column were 0.030 mg/g, 0.017 mg/g, and 0.014 mg/g respectively. This is the first study to demonstrate that recycled materials can successfully be integrated into a biofilter as an effluent polishing step to remove nutrients from anammox wastewater.

Effect of Operational Parameters on the Removal of Carbamazepine and Nutrients in a Submerged Ceramic Membrane Bioreactor

Pharmaceuticals and personal care products have raised significant concerns because of their extensive use, presence in aquatic environments, and potential impacts on wildlife and humans. Carbamazepine was the most frequently detected pharmaceutical residue among pharmaceuticals and personal care products. Nevertheless, the low removal efficiency of carbamazepine by conventional wastewater treatment plants was due to resistance to biodegradation at low concentrations. A membrane bioreactor (MBR) has recently attracted attention as a new separation process for wastewater treatment in cities and industries because of its effectiveness in separating pollutants and its tolerance to high or shock loadings. In the current research, the main and interaction effects of three operating parameters, including hydraulic retention time (12-24 h), dissolved oxygen (1.5-5.5 mg/L), and sludge retention time (5-15 days), on removing carbamazepine, chemical oxygen demand, ammonia nitrogen, and phosphorus using ceramic membranes was investigated by applying a two-level full-factorial design analysis. Optimum dissolved oxygen, hydraulic retention time, and sludge retention time were 1.7 mg/L, 24 h, and 5 days, respectively. The research results showed the applicability of the MBR to wastewater treatment with a high carbamazepine loading rate and the removal of nutrients.

Efficiency studies of modified IFAS-OSA system upgraded by an anoxic sludge holding tank

An upgraded integrated fixed-film activated sludge-oxic settling anoxic (IFAS-OSA) system is a new technology for reducing nutrients and excess sludge. The results showed that the average TN removal efficiency of the IFAS-OSA system was gradually increased up to 7.5%, while the PO₄^–3-P removal efficiency increased up-to 27%, compared with that of the IFAS system. The COD removal efficiency of the IFAS-OSA system was slightly increased up-to 5.4% and TSS removal efficiency increased up to 10.5% compared with the control system. Biomass yield coefficient (Y_obs) in the IFAS and IFAS-OSA systems were 0.44 and 0.24 (gr MLSS/ gr COD). Hence, sludge production decreased by 45%. The average SVI was decreased by 48% in IFAS-OSA system compared with IFAS. This study demonstrated the better performance of the IFAS-OSA system compared to that of the IFAS system.

Recent technologies for nutrient removal and recovery from wastewaters: A review

Water scarcity and its pollution has become a concern in recent times. The disposal of nutrient-rich (nitrogen and phosphorous) wastewater is also one of the main cause of water pollution through eutrophication, reduced dissolved oxygen that poses threat to aquatic ecosystems. As a result, nutrient removal has become a mandate apart from the removal of organics. However, the removal of nutrients from sewage is a challenging task. Conversely, conventional biological treatment processes provide little relief in nutrient removal. The treated effluents from conventional biological processes do not achieve the stringent nutrient removal disposal standard limits and become primary cause of pollution in the receiving water bodies. This has stressed upon the need for eco-friendly, low-energy and cost-efficient nutrient removal treatment technologies. Various biological treatment combinations or variants are in use for the efficient removal of nutrients. The biological processes in itself or in combination with chemical processes are preferred over technologies based solely on physico-chemical processes for its treatment performance at lower cost. This review summarizes the existing treatment processes and their possible up-gradation with the aim to accomplish the marked effluent standards for the nutrients. The concept of conventional systems and advanced systems for nutrients (nitrogen and phosphorous) removal which are already developed or under development are deeply discussed. Further, the challenges of each treatment systems are abridged. Finally, the possible suggestions for the modification/retrofitting of existing treatment systems for achieving stringent disposal standards are pointed out.

Domestic wastewater treatment in a coupled sequential batch reactor-electrochemical reactor process

The effectiveness of a sequenced biological-physicochemical reactor system for treating sewage was studied. The biological degradation was conducted in a Sequential Batch Reactor, which had innovative features for simplifying the operation and maintenance of the reactor. The reactor was operated at 4, 6, 8, and 12 hr cycle. Up to 82% removal of Chemical Oxygen Demand (COD), 50% removal of Dissolved Organic Carbon (DOC), 45% removal of Total Nitrogen (TN), and 45% removal of Total Phosphorus (TP) were achieved. The treated effluent was further polished in a continuous-flow bipolar-mode electrochemical reactor to remove additional recalcitrant organic matter from the wastewater. The process parameters were optimized using Response Surface Methodology. At the optimum condition (pH = 8.7; Current = 1.0; reaction time = 9.0), up to 90% removal of COD, 67% removal of DOC, 61% removal of TN, and 99.9% removal of TP were achieved in the coupled system. Micropollutants belonging to Pharmaceutically Active Compounds, pesticides, etc., were significantly removed. The coupled system completely removed Salmonella, Pseudomonas, and Staphylococcus. However, coliforms were detected at the outlet samples. A UV or ozone disinfection treatment is recommended for the safe reuse of the treated water for nonpotable purposes. PRACTIONER POINTS: Sequential sequential batch reactor-electrochemical reactor process (SBR-ECR) technology is effective for micropollutant removal from sewage. The coupled SBR-ECR system requires less footprint compared to conventional biological systems for wastewater treatment. Carbon material balance study revealed that more than 60% of carbon escapes from wastewater in the form of CO₂.

Pharmaceutical compound removal efficiency by a small constructed wetland located in south Brazil

The fate of pharmaceuticals during the treatment of effluents is of major concern since they are not completely degraded and because of their persistence and mobility in environment. Indeed, even at low concentrations, they represent a risk to aquatic life and human health. In this work, fourteen pharmaceuticals were monitored in a constructed wetland wastewater treatment plants (WWTP) assessed in both influent and effluent samples. The basic water quality parameters were evaluated, and the removal efficiency of pharmaceutical, potential for bioaccumulation, and the impact of WWTP were assessed using Polar Organic Chemical Integrative Sampler (POCIS) and biofilms. The pharmaceutical compounds were quantified by High Performance Liquid chromatography coupled to mass spectrometry. The sampling campaign was carried out during winter (July/2018) and summer (January/2019). The WWTP performed well regarding the removal of TSS, COD, and BOD₅ and succeeded to eliminate a significant part of the organic and inorganic pollution present in domestic wastewater but has low efficiency regarding the removal of pharmaceutical compounds. Biofilms were shown to interact with pharmaceuticals and were reported to play a role in their capture from water. The antibiotics were reported to display a high risk for aquatic organisms.

Real Wastewater Treatment Using a Moving Bed and Wastewater-Borne Algal–Bacterial Consortia with a Short Hydraulic Retention Time

Algal–bacterial consortium is a promising technology, combined with wastewater treatment plants, because algae produce molecular oxygen for nitrification and organic removal and reduce carbon dioxide emissions. However, algal–bacterial consortia based on suspended growth require a relatively long hydraulic retention time (HRT) of 4 d to 6 d for removal of organic matter and nutrients. For the algal–bacterial consortia in a photobioreactor (PBR) containing a moving bed, the organic matter and nutrient removal and the community structure of algal–bacterial consortia were investigated to determine the performance under a relatively short HRT of 2.5 d. Moving media containing algal–bacterial consortia enhanced the photosynthetic oxygen concentration (0.2 mg dissolved oxygen (DO)·L−1 to 5.9 mg DO·L−1), biochemical oxygen demand removal (88.0% to 97.2%), ammoniacal nitrogen removal (33.8% to 95.3%), total nitrogen removal (61.6% to 87.7%), total phosphate removal (66.4% to 88.7%), algal growth (149.3 mg algae·L−1 to 285.4 mg algae·L−1), and settleability (algae removal efficiency of 20.6% to 71.2%) compared with those of a PBR without moving media (SPBR). Although biomass uptake was the main mechanism for nutrient removal in the SPBR, both biomass uptake and denitrification were the main mechanisms in the PBR with moving media (MBPBR). The bacterial community also changed under the moving media condition. This study shows that moving media might be an essential parameter for PBRs with a short HRT to enhance nutrient removal and settleability.

Recent progress in integrated fixed-film activated sludge process for wastewater treatment: A review

Integrated fixed-film activated sludge (IFAS) process is considered as one of the leading-edge processes that provides a sustainable solution for wastewater treatment. IFAS was introduced as an advancement of the moving bed biofilm reactor by integrating the attached and the suspended growth systems. IFAS offers advantages over the conventional activated sludge process such as reduced footprint, enhanced nutrient removal, complete nitrification, longer solids retention time and better removal of anthropogenic composites. IFAS has been recognized as an attractive option as stated from the results of many pilot and full scales studies. Generally, IFAS achieves >90% removals for combined chemical oxygen demand and ammonia, improves sludge settling properties and enhances operational stability. Recently developed IFAS reactors incorporate frameworks for either methane production, energy generation through algae, or microbial fuel cells. This review details the recent development in IFAS with the focus on the pilot and full-scale applications. The microbial community analyses of IFAS biofilm and floc are underlined along with the special emphasis on organics and nitrogen removals, as well as the future research perspectives.

Performance and bacterial community structure of a novel inverse fluidized bed bioreactor (IFBBR) treating synthetic municipal wastewater

The performance of a lab-scale integrated anoxic and aerobic inverse fluidized bed bioreactors (IFBBR) for biological nutrient removal from synthetic municipal wastewater was studied at chemical oxygen demand (COD) loading rates of 0.34-2.10 kg COD/(m³-d) and nitrogen loading rates of 0.035-0.213 kg N/(m³-d). Total COD removal efficiencies of >84% were achieved, concomitantly with complete nitrification. The overall nitrogen removal efficiencies were >75%. Low biomass yields of 0.030-0.101 g VSS/g COD were achieved. Compared with other FBBR systems, the energy consumption for this IFBBR system was an average 59% less at organic loading rates (OLRs) of 1.02 and 2.10 kg COD/(m³-d). Bacterial community structures of attached and suspended biomass revealed that the dominant phyla were Proteobacteria, Bacteroidetes, and Epsilonbacteraeota, etc. The relative abundance of ammonia-oxidizing bacteria (AOBs) and nitrite-oxidizing bacteria (NOBs) in the aerobic attached biomass were 0.451% and 0.110%, respectively. COD mass balance in the anoxic zone was closed by consideration of sulfate reduction, which was confirmed by the presence of genus Chlorobium (sulfate-reducing bacteria) in the anoxic attached biofilm with a relative abundance of 0.32%.

Quantify the contribution of anammox for enhanced nitrogen removal through metagenomic analysis and mass balance in an anoxic moving bed biofilm reactor

In this study, enhanced nitrogen removal through in situ enrichment of anammox bacteria was successfully obtained in a full-scale municipal wastewater treatment plant (WWTP). The WWTP was an anaerobic-anoxic-oxic (AAO) process and upgraded by adding moving carriers into the anoxic zone. Enhanced nitrogen removal was obtained during almost two years of operation. The significant nitrogen removal might be associated with the in situ enrichment of anammox bacteria on the adding carriers, as revealed by the comprehensive results of molecular analysis and ¹⁵N-stable isotope tracing tests. Quantitative PCR results indicated that anammox bacteria in the anoxic-carrier biofilms presented a higher abundance than flocculent sludge (16S rRNA: P < 0.005; HzsB: P < 0.042). The 16S rRNA amplicon sequencing showed significant differences in the phylum Planctomycetes (P < 0.001) between anoxic-carrier biofilms and flocculent sludge. And metagenomic sequencing analysis further revealed the anammox relative abundance in the anoxic-carrier biofilms was significantly higher than the reported level in the flocculent sludge of conventional WWTPs. In addition, ¹⁵N-stable isotope tracing tests showed that anammox could be combined with nitrate reduction by the anoxic-carrier biofilms. Thus, enriched anammox bacteria might contribute to nitrogen loss and lead to improvements in the nitrogen removal, which was also supported by the mass balance analysis of organic carbon, nitrogen, and phosphorus of the WWTP. Overall, this study suggests that anoxic-carrier biofilms might be a candidate to enhance nitrogen removal through partial anammox in municipal WWTPs.

Performance evaluation of a decentralized wastewater treatment system in India

A Decentralized Wastewater Treatment System (DEWATS) provides an economically feasible and efficient wastewater treatment solution especially in developing countries. It has an enormous potential for developing a sustainable environmental sanitation system. In this study, the treatment efficiency of eight DEWATS plants was evaluated in the state of Maharashtra, India, for their performance in terms of selected physico-chemical parameters of the wastewater. Although the efficiency of some of the plants was lower than that reported in literature, the effluent quality of all the plants was within the permissible discharge limits of the Central Pollution Control Board for all the parameters. Comprehensive assessment of Plant I was carried in terms of its technical and socio-economic aspects. Moreover, LCA tool has been utilized to evaluate the environmental impacts of the operation stage of DEWATS. The midpoint, CML 2001 (April 2015) methodology was adopted, in which 11 impact categories were considered. From the life cycle impact assessment and interpretation, the main impacts are identified as releases of COD, P-PO₄^3-, and N-NH₄⁺ to water bodies and disposal of sludge. Due to negligible energy consumption, the operation stage was found to be less damaging to the environment. It was concluded that DEWATS can be a good alternative for treating wastewater with negligible energy and chemical consumption.

The influence of solid retention time on IFAS-MBR systems: analysis of system behavior

A University of Cape Town Integrated Fixed-Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant was operated at different values of the sludge retention time (SRT). Three SRTs were investigated at different durations: indefinitely, 30 and 15 days. The organic carbon, nitrogen and phosphorus removal, kinetic/stoichiometric parameters, membrane fouling tendency and sludge filtration properties were assessed. The findings showed that by decreasing the SRT, the pilot plant could maintain excellent carbon removal efficiencies throughout the experiments. In contrast, the biological carbon removal showed a slight nitrification and was slightly affected by the decrease of the SRT, showing high performance (approximately 91%, on average). Thus, the biofilm might have helped sustain the nitrification throughout the experiments. The average phosphorus removal performance increased slightly with a decrease in SRT, achieving the maximum efficiency (61.5%) at a SRT of 15 days. After a 30-day SRT, an increase in resistance due to pore blocking and a general worsening of the membrane filtration properties occurred.

Influence of various operating conditions on wastewater treatment in an AS-biofilm reactor and post-treatment using TiO2-based solar/UV photocatalysis

In the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT) and dissolved oxygen (DO) on chemical oxygen demand (COD) and nutrient removal from wastewater was investigated in a lab-scale activated sludge (AS)-biofilm reactor. Furthermore, in order to improve the quality of the treated wastewater, photocatalysis by TiO₂ was investigated as a post-treatment technology, using solar and UV irradiations. The AS-biofilm reactor provided a substantial removal efficiency in terms of COD, ammonia nitrogen (NH4+-N) , total nitrogen (TN) and total phosphorous when the system was maintained at C/N ratio 6.66, X in the range 2-2.5 g/L, HRT 10 h, DO in the range of 3.5-4.5 mg/L and organic loading rate (OLR) of 0.96 kg COD/m³d during Run 1. Similarly, when the reactor was maintained at C/N ratio 10, X in the range of 3-3.5 g/L, HRT 8 h, DO in the range of 3.5-4.5 mg/L and OLR of 1.8 kg COD/m³d during Run 2. The microstructure of suspended and attached biomass comprised a dense bacterial structure of cocci and bacillus microorganisms. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, most probable number and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50%, respectively.

Enhanced biodiesel industry wastewater treatment via a hybrid MBBR combined with advanced oxidation processes: analysis of active microbiota and toxicity removal

In the present study, a multistage route is proposed for the treatment of biodiesel industry wastewater (BWW) containing around 1000 mg L^-1 of total organic carbon (TOC), 3500 mg L^-1 of chemical oxygen demand (COD), and 1325 mg L^-1 of oil and grease. Initially, BWW aerobic biodegradability was assessed via Zhan-Wellens biodegradability test to confirm the appropriate treatment route. Then, a hybrid moving bed bioreactor (MBBR) system was chosen as the first treatment stage. The hybrid MBBR achieved 69 and 68% removal of COD and TOC removals, respectively, and provided great conditions for biomass growth. The bacterial community present in the hybrid MBBR was investigated by PCR-DGGE and potential biodegraders were identified such as: members of Desulfuromonadales, Nocardioidaceae and Pseudomonadaceae. Since biodegradation in the hybrid MBBR alone was unable to meet quality requirements, advanced oxidation processes, such as Fenton and photo-Fenton, were optimized for application as additional treatment stages. Physicochemical properties and acute toxicity of BWW were analyzed after the multistage routes: hybrid MBBR + Fenton, hybrid MBBR + photo-Fenton and hybrid MBBR + UV-C_254nm/H₂O₂. Hybrid MBBR + Fenton or photo-Fenton showed overall COD removal efficiencies greater than 95% and removed acute toxicity, thus being appropriate integrated routes for the treatment of real BWW. Graphical abstract ᅟ.

Simultaneous removal of atrazine and organic matter from wastewater using anaerobic moving bed biofilm reactor: A performance analysis

In this study, an anaerobic moving bed biofilm reactor (AMBBR) was designed to biodegrade atrazine under mesophilic (32 °C) condition and then it was evaluated for approximately 1 year. After biofilm formation, acclimation, and enrichment of microbial population within the bioreactor, the effect of various operation conditions such as changes in the concentration of influent atrazine and sucrose, hydraulic retention time (HRT), and salinity on the removal of atrazine and chemical oxygen demand (COD) were studied. In optimum conditions, the maximum removal efficiency of atrazine and COD was 60.5% and 97.4%, respectively. Various models were developed to predict the performance of atrazine removal as a function of HRT during continuous digestion. Also, coefficients kinetics was studied and the maximum atrazine removal rate was determined by Stover - Kincannon model (rmax = 0.223 kgATZ/m3d). Increasing salinity up to 20 g/L NaCl in influent flow could inhibit atrazine biodegradation process strongly in the AMBBR reactor; whereas, the reactor could tolerate the concentrations less than 20 g/L easily. Results showed that AMBBR is feasible, easy, affordable, so suitable process for efficiently biodegrading toxic chlorinated organic compounds such as atrazine. There was no accumulation of atrazine in the biofilm and the loss of atrazine in the control reactor was negligible; this shows that atrazine removal mechanism in this system was due to co-metabolism.

Technical, hygiene, economic, and life cycle assessment of full-scale moving bed biofilm reactors for wastewater treatment in India

Moving bed biofilm reactor (MBBR) is a highly effective biological treatment process applied to treat both urban and industrial wastewaters in developing countries. The present study investigated the technical performance of ten full-scale MBBR systems located across India. The biochemical oxygen demand, chemical oxygen demand, total suspended solid, pathogens, and nutrient removal efficiencies were low as compared to the values claimed in literature. Plant 1 was considered for evaluation of environmental impacts using life cycle assessment approach. CML 2 baseline 2000 methodology was adopted, in which 11 impact categories were considered. The life cycle impact assessment results revealed that the main environmental hot spot of this system was energy consumption. Additionally, two scenarios were compared: scenario 1 (direct discharge of treated effluent, i.e., no reuse) and scenario 2 (effluent reuse and tap water replacement). The results showed that scenario 2 significantly reduce the environmental impact in all the categories ultimately decreasing the environmental burden. Moreover, significant economic and environmental benefits can be obtained in scenario 2 by replacing the freshwater demand for non-potable uses. To enhance the performance of wastewater treatment plant (WWTP), there is a need to optimize energy consumption and increase wastewater collection efficiency to maximize the operating capacity of plant and minimize overall environmental footprint. It was concluded that MBBR can be a good alternative for upgrading and optimizing existing municipal wastewater treatment plants with appropriate tertiary treatment. Graphical abstract ᅟ.

Bacterial community structure and removal performances in IFAS-MBRs: A pilot plant case study

The paper reports the results of an experimental campaign carried out on a University of Cape Town (UCT) integrated fixed-film activated sludge (IFAS) membrane bioreactor (MBR) pilot plant. The pilot plant was analysed in terms of chemical oxygen demand (COD) and nutrients removal, kinetic/stoichiometric parameters, membrane fouling and sludge dewaterability. Moreover, the cultivable bacterial community structure was also analysed. The pilot plant showed excellent COD removal efficiency throughout experiments, with average value higher than 98%, despite the slight variations of the influent wastewater. The achieved nitrification efficiency was close to 98% for most of the experiments, suggesting that the biofilm in the aerobic compartment might have sustained the complete nitrification of the influent ammonia, even for concentrations higher than 100 mg L^-1. The irreversible resistance due to superficial cake deposition was the mechanism that mostly affected the membrane fouling. Moreover, it was noticed an increase of the resistance due pore blocking likely due to the increase of the EPS_Bound fraction that could derive by biofilm detachment. The bacterial strains isolated from aerobic tank are wastewater bacteria known for exhibiting efficient heterotrophic nitrification-aerobic denitrification and producing biofilm.

Combined organic matter and nitrogen removal from a chemical industry wastewater in a two-stage MBBR system

Pesticide-producing factories generate highly polluting wastewaters containing toxic and hazardous compounds which should be reduced to acceptable levels before discharge. In this study, a chemical industry wastewater was treated in a pre-denitrification moving-bed biofilm reactor system subjected to an increasing internal mixed liquor recycle ratio from 2 to 4. Although the influent wastewater characteristics substantially varied over time, the removal of chemical oxygen demand (COD) and dissolved organic carbon was quite stable and mostly higher than 90%. The highest fraction of the incoming organic matter was removed anoxically, favouring a low COD/N environment in the subsequent aerobic nitrifying tank and thus ensuring stable ammonium removal (90-95%). However, during pH and salt shock periods, nitrifiers were severely inhibited but gradually restored their full nitrifying capability as non-stressing conditions were reestablished. Besides promoting an increase in the maximum nitrification potential of the aerobic attached biomass from 0.34 to 0.63 mg [Formula: see text], the increase in the internal recycle ratio was accompanied by an increase in nitrogen removal (60-78%) and maximum specific denitrification rate (2.7-3.3 mg NOx(-)--N). Total polysaccharides (PS) and protein (PT) concentrations of attached biomass were observed to be directly influenced by the influent organic loading rate, while the PS/PT ratio mainly ranged from 0.3 to 0.5. Results of Microtox tests showed that no toxicity was found in the effluent of both the anoxic and aerobic reactors, indicating that the biological process was effective in removing residual substances which might adversely affect the receiving waters' ecosystem.

Study of moving bed biofilm reactor in diethyl phthalate and diallyl phthalate removal from synthetic wastewater

Phthalic acid esters have received significant attention over the last few years since they are considered as priority pollutants. In this study, effects of different operation conditions including hydraulic retention time, phthalates loading rates and aeration rate on process performance of moving bed biofilm reactor (MBBR) for removing diethyl phthalate (DEP) and diallyl phthalate (DAP) from synthetic wastewater was evaluated. In optimum conditions, 94.96% and 93.85% removal efficiency were achieved for DEP and DAP, respectively. Moreover, MBBR achieved to remove more than 92% of COD for both phthalates. The results showed that DEP had a higher biodegradation rate compared to DAP, according to the selected parameters such as half saturation constant, overall reaction rate and maximum specific growth rate. The Grau second order model found as the best model for predicting MBBR performance due to its high correlation coefficients and more conformity of its kinetic coefficients to the results.

Enhancing nitrogen and phosphorus removal in the BUCT-IFAS process by bypass flow strategy

A University of Cape Town process coupled with integrated fixed biofilm and activated sludge system was modified by bypass flow strategy (BUCT-IFAS) to enhance nitrogen and phosphorus removal from the wastewater containing insufficient carbon source. This process was operated under different bypass flow ratios (λ were 0, 0.4, 0.5, 0.6 and 0.7, respectively) to investigate the effect of different operational modes on the nitrogen (N) and phosphorus (P) removal efficiency (λ=0 was noted as common mode, other λ were noted as bypass flow mode), and optimizing the N and P removal efficiency by altering the λ. Results showed that the best total nitrogen (TN) and total phosphorus (TP) removal performances were achieved at λ of 0.6, the effluent TN and TP averaged 14.0 and 0.4 mg/L meeting discharge standard (TN<15 mg/L, TP<0.5 mg/L). Correspondingly, the TN and TP removal efficiencies were 70% and 94%, respectively, which were 24 and 41% higher than those at λ of 0. In addition, the denitrification and anoxic P-uptake rates were increased by 23% and 23%, respectively, compared with those at λ of 0. These results demonstrated that the BUCT-IFAS process was an attractive method for enhancing nitrogen and phosphorus removal from wastewater containing insufficient carbon source.

Nitrogen removal from high organic loading wastewater in modified Ludzack-Ettinger configuration MBBR system

A moving bed biofilm reactor with pre-denitrification configuration was fed with a synthetic wastewater containing high chemical oxygen demand (COD) and ammonia. By changing different variables including ammonium and COD loading, nitrification rate in the aerobic reactor and denitrification rate in the anoxic reactor were monitored. Changing the influent loading was achieved via adjusting the inlet COD (956-2,096 mg/L), inlet ammonium (183-438 mg/L), and hydraulic retention time of the aerobic reactor (8, 12, and 18 hours). The overall organic loading rate was in the range of 3.60-17.37 gCOD/m2·day, of which 18.5-91% was removed in the anoxic reactor depending on the operational conditions. Considering the complementary role of the aerobic reactor, the overall COD removal was in the range 87.3-98.8%. In addition, nitrification rate increased with influent ammonium loading, the maximum rate reaching 3.05 gNH4/m2·day. One of the most important factors affecting nitrification rate was influent C:N entering the aerobic reactor, by increasing which nitrification rate decreased asymptotically. Nitrate removal efficiency in the anoxic reactor was also controlled by the inlet nitrate level entering the anoxic reactor. Furthermore, by increasing the nitrate loading rate from 0.91 to 3.49 gNO/m3·day, denitrification rate increased from 0.496 to 2.47 gNO/m3·day.

Evaluation of different wastewater treatment processes and development of a modified attached growth bioreactor as a decentralized approach for small communities

This study was undertaken to evaluate the potential future use of three biological processes in order to designate the most desired solution for on-site treatment of wastewater from residential complexes, that is, conventional activated sludge process (CASP), moving-bed biofilm reactor (MBBR), and packed-bed biofilm reactor (PBBR). Hydraulic retention time (HRT) of 6, 3, and 2 h can be achieved in CASP, MBBR, and PBBR, respectively. The PBBR dealt with a particular arrangement to prevent the restriction of oxygen transfer efficiency into the thick biofilms. The laboratory scale result revealed that the overall reduction of 87% COD, 92% BOD₅, 82% TSS, 79% NH₃-N, 43% PO₄-P, 95% MPN, and 97% TVC at a HRT of 2 h was achieved in PBBR. The microflora present in the system was also estimated through the isolation, identification, and immobilization of the microorganisms with an index of COD elimination. The number of bacterial species examined on the nutrient agar medium was 22 and five bacterial species were documented to degrade the organic pollutants by reducing COD by more than 43%. This study illustrated that the present PBBR with a specific modified internal arrangement could be an ideal practice for promoting sustainable decentralization and therefore providing a low wastage sludge biomass concentration.

Influence of filling ratio and carrier type on organic matter removal in a moving bed biofilm reactor with pretreatment of electrocoagulation in wastewater treatment

At present, there is great concern about limited water resources and water quality, which require a more advanced technology. The Moving Bed Biofilm Reactor (MBBR) has been shown to be an efficient technology for removal of organic matter and nutrients in industrial and urban wastewater treatment. However, there are some pollutants which are more difficult to remove by biological processes, so this process can be improved with additional physical and chemical treatments such as electrocoagulation, which appears to be a promising technology in electrochemical treatments. In this research, urban wastewater was treated in an MBBR plant with an electrocoagulation pre-treatment. K1 from AnoxKaldnes and AQWISE ABC5 from Aqwise were the carriers studied under three different filling ratios (20, 35, and 50%). The experimental pilot plant had four bioreactors with 20 L of operation volume and a common feed tank with 100 L of operation volume. The movement of the carriers was generated by aeration and stirrer systems. Organic matter removal was studied by analysis of soluble chemical oxygen demand (sCOD). The maximum organic matter removal in this MBBR system was 65.8% ± 1.4% and 78.4% ± 0.1% for K1 and Aqwise ABC5 carriers, respectively. Moreover, the bacterial diversity of the biofilm was studied by temperature-gradient gel electrophoresis (TGGE) of PCR-amplified partial 16S rRNA genes. 20 prominent TGGE bands were successfully reamplified and sequenced, being the predominant population: β-Proteobacteria, α-Proteobacteria, and Actinobacteria.

Innovative anaerobic/upflow sludge blanket filtration bioreactor for phosphorus removal from wastewater

Phosphorus is the key element to remove from aquatic environments to limit the growth of aquatic plants and algae and, thus, to control eutrophication. Because the upflow sludge blanket filtratio' (USBF) process, without addition of metal salts, entails low efficiency for phosphorus removal, we added an anaerobic reactor to the USBF bioreactor in order to promote the simultaneous removal of phosphorus and nitrogen from wastewater. The results revealed that the anaerobic/USBF bioreactor had a phosphorus removal efficiency up to 86%, with a sludge retention time (SRT) of 10 days, a hydraulic retention time (HRT) of 24 hours and an optimum COD/N/P ratio of 100/5/1. This ratio also improved the compaction quality of the sludge blanket in the USBF clarifier. The average specific phosphate uptake rate in the aerobic zone and the average specific phosphate release rate in the anaerobic reactor were 0.014 mg PO4-P removed/(g VSS x min) and 0.0525 mg PO4-P released/(g VSS x min), respectively. Secondary phosphorus release in the USBF clarifier was heightened with increasing HRT. Hence, the optimum total HRT can be selected between 16 and 24 hours based on effluent quality. Effluent phosphorus of about 1 mg/L was provided for wastewater with the COD/N/P ratio of 100/5/1 at the sludge age of 10 days and total HRT of 16 hours. This study illustrated that the anaerobic/USBF bioreactor at the optimum operational conditions can be an effective process for phosphorus removal from municipal wastewater.