Biodegradable Organic Matter Research Articles

A review on microbial fuel cell technology for Brewery industry wastewater treatment – From fundamentals to pilot scale studies

AbstractIndustries play an important role in the economic growth of any nation, whereas they release pollutants, which impact our environment seriously. Owing to the rapid climate change and global warming, our earth is searching for different sustainable energy technologies. Microbial fuel cell technology is emerging as one of the most versatile sustainable energy technology, with their ability to tap the energy stored in the wastewater and convert it directly into electrical energy. Though MFC research is still in its nascent stage, its theoretical superiority makes it a unique technology, which can be developed into a self‐sufficient system for wastewater treatment in the near future. Brewery industries consume large quantities of water for beer production and hence release large quantities of wastewater. The chemical energy stored in the brewery wastewater could be converted into useful bioelectricity by MFC technology compared to other traditional wastewater treatment technologies, which are all energy intensive. Brewery wastewater, rich in biodegradable organic matter with their non‐toxic nature, makes it a highly suitable substrate for MFC. It is one of the few substrates that have made it to pilot‐scale studies worldwide. This study aims to review the microbial fuel cells with brewery wastewater as their substrate. It will elaborate the different configurations of MFCs employed for brewery wastewater so far, their power producing ability and wastewater treatment efficiency. The critical factors that influence these MFC systems will also be discussed. Finally, this article also identifies and suggests different strategies to improve the performance of such MFC systems.

Impact of sonication on the algal organic matter characteristics of Anabaena circinalis, Microcystis aeruginosa, and Chlorella vulgaris

The frequent occurrence of harmful algal blooms (HABs) in drinking water reservoirs causes water treatment and supply problems. Ultrasonication is a physicochemical treatment method used to treat HABs. During the ultrasonication of HABs, algal organic matter (AOM), including both extracellular organic matter (EOM) and intracellular organic matter (IOM), is released and changes the dissolved organic matter characteristics. In this study, Anabaena circinalis (A. circinalis), Microcystis aeruginosa (M. aeruginosa), and Chlorella vulgaris (C. vulgaris) were used to investigate changes in AOM characteristics during ultrasonication using a fluorescence excitation-emission matrix and assimilable organic carbon. We found that ultrasonication increased the dissolved AOM content, resulting in increased dissolved organic carbon from IOM released from algal cells. A. circinalis, M. aeruginosa, and C. vulgaris had dissolved organic carbon concentrations of 22.5, 3.8, and 6.7 mg/L before sonication, which increased to 29.1, 10.8, and 7.7 mg/L after ultrasonication, respectively. Additionally, the IOM released during ultrasonication held more protein-like substances and was mostly associated with biodegradable organic matter.

Electroactive Bacteria in Natural Ecosystems and Their Applications in Microbial Fuel Cells for Bioremediation: A Review

Electroactive bacteria (EAB) are natural microorganisms (mainly Bacteria and Archaea) living in various habitats (e.g., water, soil, sediment), including extreme ones, which can interact electrically each other and/or with their extracellular environments. There has been an increased interest in recent years in EAB because they can generate an electrical current in microbial fuel cells (MFCs). MFCs rely on microorganisms able to oxidize organic matter and transfer electrons to an anode. The latter electrons flow, through an external circuit, to a cathode where they react with protons and oxygen. Any source of biodegradable organic matter can be used by EAB for power generation. The plasticity of electroactive bacteria in exploiting different carbon sources makes MFCs a green technology for renewable bioelectricity generation from wastewater rich in organic carbon. This paper reports the most recent applications of this promising technology for water, wastewater, soil, and sediment recovery. The performance of MFCs in terms of electrical measurements (e.g., electric power), the extracellular electron transfer mechanisms by EAB, and MFC studies aimed at heavy metal and organic contaminant bioremediationF are all described and discussed.

Processing of Biodegradable Waste from Ceremonial Activities in Bali with Black Soldier Fly (BSF) Larvae

The conducted study aimed to analyze the waste processing process from traditional ceremonies in Bali by examining the composition of the waste generated. Since most of the waste generated during these ceremonies is a biodegradable organic material, it is feasible to use sustainable bioconversion techniques such as Black Soldier Fly (BSF) larvae to convert this waste into useful products. In the study, a feeding trial was conducted using a garbage blender consisting of banana fruit, rice, banana leaf, coconut leaf, and flower wastes. The BSF larvae were fed at a rate of 40 mg/larvae per day with a total of 200 larvae. The researchers measured the key processing parameters including overall degradation (OD), waste reduction index (WRI), and feed conversion efficiency (ECD) which resulted in values of 41.27±0.42%, 3.30±0.03 g/day, and 7.82±0.43%, respectively. The study found that the dry residue produced during the process was around 30-31% and met the minimum standards set for compost or biomass fuel. Additionally, the total mass of BSF larvae produced was around 16-18% in one cycle, which is a high protein source that can be used to feed animals.

Enhanced anaerobic digestion of waste activated sludge by alkaline protease-catalyzing hydrolysis: Role and significance of initial pH adjustment

Anaerobic digestion has been regarded as a preferred technology for carbon/energy recovery from waste activated sludge via volatile fatty acids (VFAs) and methane production. Although the enzyme pretreatment has been investigated, specific roles of initial pH adjustment on alkaline protease (AP) catalysis and its influence on anaerobic digestion have been rarely reported. This work demonstrated that the increasing initial pH displayed positive mutual promotion of AP-catalyzing hydrolysis for facilitating sludge solid reduction and biodegradable organic matter solubilization. The release of carbon source and phosphorus were also promoted, while the soluble NH4+-N content was decreased at increasing alkaline conditions, which was beneficial for hydrolysate bio-utilization. Nevertheless, initial pH = 10 was the optimum condition for maximizing VFAs and methane recovery after AP-catalyzing sludge hydrolysis. Under such condition, the sludge solid reduction and sludge hydrolysis rate constants were 0.7981 h−1 and 1.1288 h−1, respectively, which were 6.40 and 2.45 times higher than those in the control. Meanwhile, the biochemical acidogenic potential of 447.0 mg COD VFAs/g VSS and the estimated biochemical methane potential of 437.6 mL CH4/g VSS were achievable. The identification of the mutual promotion distribution revealed that initial pH adjustment presented more close association with anaerobic digestion than AP catalysis and its contribution was amplified with increasing pH. Apparently, such AP catalysis with initial pH adjustment is a promising technology for sustainable sludge management with economic benefits and carbon-emission reduction.

Analogous study of cumulative biogas production by anaerobic digestion of sewage treatment plant sludge, the proposal of universal dimensionless models

AbstractThe current global concern is how to replace polluting fossil fuels with sustainable green fuels. On this basis, in this study, a characterization protocol for sewage sludge in Algeria was carried out. Their objective was to study the process of anaerobic digestion for biogas production by analogy to experiments that have already been made in the literature. The performance of the proposed models has been validated with experimental data from the scientific literature. Biodegradable organic matter levels are high (160–500 mg L−1) giving an acceptable yield for biogas production. The modeling of cumulative biogas production was carried out by Gompertz and models were proposed for different products. It has been observed that there is a better agreement of the models proposed with the experimental data with a maximum value of r2 = 0.9996. The modeling of the degradation of organic matter was carried out by the first order‐model, and dimensionless models were proposed. The latter gave a good agreement with the experimental data better than the model in the literature, with a maximum value of r2 = 0.9985. The proposed models to study the anaerobic digestion process of organic matter, as well as those related to the process of cumulative biogas production, are universal (without units of measurement), which will help producers in this field to improve production, as well as reduce the investment cost through preliminary simulations.

Methanogenesis and metal leaching on anaerobic decomposition of graptolite argillite

Estonian sedimentary deposits (e.g., graptolite argillite) with relatively high content of organic matter and metals (V, Mo, U and Zn) are habitat for microorganisms. Metals exist in argillite as sulfides, in the composition of organometallic compounds or in silicate minerals. While the role of pyrite oxidizing microorganisms in bioleaching of metals is well described, less is known about the processes related to transformation of organometallic complexes. The current study examines impact of microorganisms on argillite organic matter decomposition as well as on metals leaching and/or precipitation. The microbial diversity of methane producing, and possible metal leaching consortium is described, the role of betaine in biodegradation of argillite organic matter is explained and a tentative mechanism for organic matter degradation with simultaneous methanogenesis is proposed.

Enhanced hydrogen and methane production from date fruit wastes using semi continuous two-stage anaerobic digestion process with increasing organic loading rates

Biological conversion of date wastes under continuous conditions is a challenge due to their high content of biodegradable organic matter. In this study, hydrogen (H2) and methane (CH4) production in a two-stage process to increase the energy recovery from date pulp wastes (DPW) was investigated. In the first stage, the effect of increasing organic leading rate (OLR) on dark fermentation (DF) performances was evaluated in a semi continuously stirred tank reactors (SCSTR) without nutrients addition. The highest volumetric H2 production rate (VHPR) and specific H2 yield (SHY) of 0.76 L/L.d and 81 LH2/kg volatile solid (VS), respectively were achieved at high OLR of 11.74 gVS/L.d. In the second stage, the DF effluent was used as substrate to feed the SCSTR of anaerobic digestion (AD). The highest volumetric methane production rate (VMPR) of 2.92 L/L.d was achieved with a high OLR (4.25 gVS/L.d) and short hydraulic retention time (HRT, 8 days), producing specific methane yield (SMY) of 530 LCH4/kgVS. Thus, the two-stage process can be an effective strategy for high rate renewable energy recovery (13 kJ/gVSinlet) and organic waste processing.

Insights into thermal hydrolysis pretreatment temperature for enhancing volatile fatty acids production from sludge fermentation: Performance and mechanism

To reveal the impact of thermal hydrolysis pretreatment (THP) temperature on the unclear mechanisms of volatile fatty acids (VFAs) production, four groups were established with different temperatures (100, 120, 140 and 160 °C), and high throughput sequencing technology was utilized. The results indicated that the optimal VFAs production occurred at 140 °C. Moreover, as the THP temperature increased, the proportion of acetic acid also increased, accounting for 10.8% to 26.7% of the VFAs, compared to only 4.9% in the control group. Mechanism investigations revealed that THP facilitated the hydrolysis and release of biodegradable organic matter. Moreover, the abundance of VFAs production and hydrolytic microorganisms and related metabolic functional genes expression were evidently improved by THP. Overall, this study deepens the understanding of the mechanisms through which different THP temperatures stimulate the production of VFAs through acidogenic fermentation, providing technical support for future THP application in sludge treatment.

Bioelectricity Generation by Single Chamber Microbial Fuel Cell by Using Platinum Catalyst as Electrode

In this study, a wet proof multiple air cathode microbial fuel cell that generates bioelectricity by biodegradation of organic matter was fabricated. In this, platinum coated (0.5 mg/cm2) carbon cloth was used as air cathode and graphite rod was used as anode. The maximum power produced by MFC was 1.65042, 0.66951, 0.425061 mW on the 2nd day of operation with 1K, 3K, 5K ohm external resistance respectively. The maximum open circuit voltage and current given by MFC was 1.557 mV and 1.06 mA respectively incorporated with 1 K ohm external resistance. It was seen that open circuit voltage (OCV) initially increases with time due to increase in microbial activity but after that there is drop in voltage possibly due to decline of available substrate for microbial population. Maximum bacterial count of 90 ×105 CFU was observed on the 3rd day of operation.

Enhanced Sorption for the Oil Spills by SDS-Modified Rice Straw.

Frequent oil spills have caused serious consequences to the ecosystem and environment. Therefore, in order to reduce and eliminate the impact of oil spills on biology and the environment, oil spill remediation materials must be considered. As a kind of cheap and biodegradable natural organic cellulose oil-absorbing material, straw has an important practical significance in the treatment of oil spills. In order to improve the ability of rice straw to absorb crude oil, rice straw was first treated with acid and was then modified with sodium dodecyl sulfate (SDS) through a simple charge effect. Finally, the performance of oil absorption was tested and evaluated. The results illustrate that the oil absorption performance was greatly improved under the conditions of 10% H2SO4, for a 90 min reaction at 90 °C, under 2% SDS, and reacted for 120 min at 20 °C, and the rate of adsorption for rice straw to crude oil was raised by 3.33 g/g (0.83 to 4.16). Then, the rice stalks before and after the modification were characterized. Contact angle analysis shows that the modified rice stalks display better hydrophobic-lipophilic properties than unmodified rice stalks. The rice straw was characterized by XRD and TGA, and the surface structure of the rice straw was characterized by FTIR and SEM, which explain the mechanism of surface-modified rice straws with SDS to improve their oil absorption capacity.

Physico-chemical characteristics and biodegradability of primary effluent and particulate matter removed by microscreens.

In this study, the physical, chemical, and biological characteristics of raw wastewater were compared with the liquid and solid streams generated by a primary clarifier (PC), a rotating belt filter (RBF, 350 μm), and a drum filter (DF, 60 μm) and series (SER) combination of an RBF with a PC or a DF using pilot-scale primary treatment units. The RBF removed about 36% of the influent total suspended solids. The DF and PC yielded an influent total suspended solid removal of 47% to 55% in both individual (parallel) and SER configurations. The size fractionation and chemical characterizations of the liquid fractions indicated a significant change in the wastewater composition in both filter configurations with no variation in the biodegradability of liquid fractions. The solids recovered by RBF had a higher total solids (TS) concentration and a higher volatile solids (VS) content (0.92 g VS/g TS) than that of DF and PC treatments (0.58 to 0.84 g VS/g TS). DF and PC sludge demonstrated a higher biodegradability rate (k1 ; 0.11 d-1 < k1 < 0.20 d-1 ) than solids recovered by RBF (0.09 d-1 ). The retained solids in the SER configuration demonstrated a significantly lower theoretical biochemical methane potential than the parallel configuration, likely due to the presence of smaller particles with a significantly higher ratio of particulate chemical oxygen demand over volatile suspended solids (1.86 to 2.40 g chemical oxygen demand/g volatile suspended solids). These results indicated that the physical, chemical, and biological characteristics of liquid and solids from different filter configurations are required to determine design criteria to upgrade or retrofit water resource recovery facilities using an RBF or a DF. PRACTITIONER POINTS: A rotating belt filter (RBF) removed less solids than a drum filter (DF) or a primary clarifier (PC). A series configuration of an RBF with either a DF or PC resulted in an effluent with a lower proportion of slowly biodegradable organic matter than in a parallel configuration. Solids from an RBF, a DF, or a PC had similar theoretical biochemical methane potential.

Coupled effects of sedimentary iron oxides and organic matter on geogenic phosphorus mobilization in alluvial-lacustrine aquifers

The organic matter (OM) biodegradation and reductive dissolution of iron oxides have been acknowledged as key factors in the release of geogenic phosphorus (P) to groundwater. However, the coupled effects of natural OM with iron oxides on the mobilization of geogenic P remain unclear. Groundwater with high and low P concentrations has been observed in two boreholes in the alluvial-lacustrine aquifer system of the Central Yangtze River Basin. Sediment samples from these boreholes were examined for their P and Fe species as well as their OM properties. The results show that sediments from borehole S1 with high P levels contain more bioavailable P, particularly iron oxide bound P (Fe-P) and organic P (OP) than those from borehole S2 with low P levels. Regarding borehole S2, Fe-P and OP show positive correlations with total organic carbon as well as amorphous iron oxides (FeOX1), which indicate the presence of Fe-OM-P ternary complexes, further evidenced by FTIR results. In a reducing environment, the protein-like component (C3) and terrestrial humic-like component (C2) will biodegrade. In the process of C3 biodegradation, FeOX1 will act as electron acceptors and then undergo reductive dissolution. In the process of C2 biodegradation, FeOX1 and crystalline iron oxides (FeOX2) will act as electron acceptors. FeOX2 will also act as conduits in the microbial utilization pathway. However, the formation of stable P-Fe-OM ternary complexes will inhibit the reductive dissolution of iron oxides and OM biodegradation, thus inhibiting the mobilization of P. This study provides new insights into the enrichment and mobilization of P in alluvial-lacustrine aquifer systems.

Enhanced purification of kitchen-oil wastewater driven synergistically by surface microelectric fields and microorganisms

The stable structure and toxic effect of refractory organic pollutants in wastewater lead to the problem of high energy consumption in water treatment technology. Herein, we propose a synergistic purification of refractory wastewater driven by microorganisms and surface microelectric fields (SMEF) over a dual-reaction-center (DRC) catalyst HCLL-S8-M prepared by an in situ growth method of carbon nitride on the Cu-Al2O3 surface. Characterization techniques demonstrate the successful construction of SMEF with strong electrostatic force over HCLL-S8-M based on cation-π interactions between metal copper ions and carbon nitride rings. With the catalyst as the core filler, an innovative fixed bed bioreactor is constructed to purify the actual kitchen-oil wastewater. The removal efficiency of the wastewater even with a very low biodegradability (BOD5/COD = 0.33) can reach 60% after passing through this bioreactor. An innovative reaction mechanism is revealed for the first time that under the condition of a small amount of biodegradable organic matter, the SMEF induces the enrichment of electric active microorganisms (Desulfobulbus and Geobacter) in the wastewater, accelerates the interspecies electron transfer of intertrophic metabolism with the biodegradable bacteria through the extracellular electron transfer mechanism such as cytochrome C and self-secreted electron shuttle. The electrons of the refractory organic pollutants adsorbed on the surface of the catalyst are delocalized by the SMEF, which can be directly utilized by microorganisms through EPS conduction. The SMEF generated by electron polarization can maximize the utilization of pollutants and microorganisms in wastewater and further enhance degradation without adding any external energy, which is of great significance to the development of water self-purification technology.

Improvement of the Sludge Decomposition and Nutrients Release by a Treatment with Potassium Permanganate Combined with an Ultrasonic Process

Ultrasonic decomposition of sludge is a popular method for sludge treatment. Potassium permanganate (KMnO4) was added to promote the reduction of sludge and hydrolysis efficiency. The effect of ultrasonic treatment (ULT) combined with potassium permanganate (KMnO4) preprocessing on the disintegration of waste activated sludge (WS) was studied in this survey. The results indicated that the combined pretreatment of KMnO4 and ULT (150 W, 20 min) significantly improved the decomposition efficiency and nutrient release efficiency of sludge. The volatile suspended solids (VSS) were lessened by 15.22%, which was 56.8% larger than that of raw sludge. The soluble proteins, soluble chemical oxygen demand (SCOD), polysaccharides, and volatile fatty acids (VFAs) were improved by 2005.1%, 464%, 669.8%, and 719.9% respectively. The deliquescent organic matter in sludge products also effectively decreased, demonstrating the effective promoting effect of KMnO4 + ULT. Mechanistic studies showed that ULT united with KMnO4 pretreatment could improve the biodegradability of soluble organic matter by generating reactive radicals, effectively disrupt the structure of cell walls, lyse extracellular polymers, and accelerate the liberation of organic matter. The composite sludge decomposition process further mitigates the harm of sludge to the environment and provides a cleaner and more efficient sludge reduction and utilization method.

Optimizing waste activated sludge disintegration by investigating multiple electrochemical pretreatment conditions: Performance, mechanism and modeling

The complex and rigid floc structure often limits the reutilization of waste activated sludge (WAS). Electrochemical pretreatment (EPT) is one of the most effective technologies that can enhance WAS disintegration. But a comprehensive investigation into how multiple EPT conditions work was rarely reported. The study evaluated the effects of multiple EPT conditions, i.e., different electrolytes (NaCl, Na2SO4, and CaCl2), electrolytes dosage (0 g/L, 0.5 g/L, 1.0 g/L, and 3.0 g/L), EPT current (0 A, 0.5 A, 1.0 A, and 3.0 A) and EPT time (0 min, 30 min, 60 min, and 90 min) on WAS disintegration. The results showed that NaCl was outstanding from other electrolytes in promoting more WAS disintegration. Besides, a relatively higher NaCl dosage, a higher EPT current, and a longer EPT time promoted more reactive chlorine species (RCS), thus enhancing WAS disintegration in terms of extracellular polymeric substances (EPS) structure destruction and biodegradable organic matter release. After EPT for 60 min at NaCl dosage of 1.0 g/L and current of 1.0 A, the EPS multilayer structure destruction, biodegradable organic matters release, and soluble chemical oxygen demand (SCOD) increase in the supernatant were enhanced by 17.2 %, 130.5 %, and 238.7 %, respectively. Then a predictive quadratic model was established and the impact significance of the above EPT factors for enhancing WAS disintegration followed dosage of NaCl > current > EPT time. Furthermore, response surface methodology (RSM) suggested NaCl dosage of 2.75 g/L, current of 2.0 A, and EPT time of 30 min were the optimal EPT conditions, bringing a 42.0 % increase in the net economic benefit of WAS treatment compared to without EPT.

Organic Compounds and Antibiotic-Resistant Bacteria Behavior in Greywater Treated by a Constructed Wetland.

Laundry greywater is considered as an alternative source of non-potable water, as it is discharged in approximately 70% of homes. Because this water contains compounds such as biodegradable and recalcitrant organic matter, surfactants, and microbiological compounds, it must be treated prior to reuse. Therefore, the objective of this study was to assess the behavior of organic matter and antibiotic-resistant bacteria (ARB) in greywater treated by a constructed wetland (CW). The results show that the organic matter removal efficiencies were 67.19%, 50.15%, and 63.57% for biological oxygen demand (BOD5), chemical oxygen demand (COD) and total organic carbon (TOC), respectively; these efficiencies were not significant (p > 0.05). In addition, the CW allows the distribution of TOC and ionic compounds in the fractions below 1000 Da to increase by 5.03% and 13.05%, respectively. Meanwhile, the treatment of microbiological compounds generated non-significant removals (p > 0.05), along with increases in bacteria resistant to the antibiotics ciprofloxacin (CIP) and ceftriaxone (CTX) of 36.34%, and 40.79%, respectively. In addition, a strong association between ARB to CIP, CTX, cationic and non-ionic surfactants was determined, indicating the role of surfactants in ARB selection. It is suggested that disinfection systems should be employed prior to the reuse of the treated water.

Characterization and analysis of fish waste as feedstock for biogas production

Abstract Fish waste (FW) is biodegradable waste that remains underutilized and causes a problem to the environment since the existing disposal techniques result in health risks and environmental pollution. FW has significant potential for producing biogas that decreases the reliance on fossil fuels because it contains easily biodegradable organic matter. The physicochemical analysis of the FW such as moisture content of 61.78%, volatile solids (VS) of 93.94%, total solids of 38.21%, ash content (AC) of 0.52%, total organic carbon of 54.2%, total Kjeldahl nitrogen of 9.2% and carbon to nitrogen (C/N) ratio of 5.89% were considered and analyzed in this research. In addition, the methane potential was determined and obtained using gas detector. The results shown that the methane (CH4) content in FW was 50.12%, which was the potential feedstock of FW for biogas production. Nevertheless, the VS of FW was high, which was good for this feedstock to be easily digested as the sign of producing biogas and demonstrates 99.9985% of performance rate. Finally, the FW had a lower C/N ratio compared with other biogas production waste. Future work needs to consider co-digestion with higher C/N ratio feedstocks.

Assessment of the Performance of a Water Treatment Plant in Ecuador: Hydraulic Resizing of the Treatment Units

Granting access to drinking water has been a challenge because 47% of the worldwide population is not connected to a drinking water distribution network in rural settlements. This study aimed to evaluate the contaminant removal efficiency in a conventional water treatment facility in the Austro region of Ecuador, Paute, to identify the treatment units requiring hydraulic resizing. Water samples were collected from each treatment unit to characterize the physical-chemical and microbiological parameters, and the dimensions of the treatment ponds for hydraulic evaluation purposes. Water hardness, electrical conductivity, SO42−, and Fe2+ were the main issues found in the water, which failed to comply with Ecuadorian technical guidelines. The treatment units, such as the flocculator, rapid sand filter, and storage tank, were resized to meet the demand of the future population. In addition, the residual free chlorine was measured as insufficient in the community’s tap water, showing an unprotected water distribution system to microbiological contamination. No disinfection by-products were found despite the existence of biodegradable organic matter. The findings of this research propose improvements in the deployed treatment practices to provide the community with drinking water in accordance with the Sustainable Development Objectives (SDG 3 and SDG 6).

Simulating the impact of ozonation on biodegradation characteristics of industrial wastewater concentrated with membrane filtration

The biodegradation of raw wastewater for an organized industrial zone has been studied by means of dedicated respirometric and analytical experiments. The experimental results indicated that the investigated industrial wastewater contains mainly the soluble (slowly) hydrolysable fraction of chemical oxygen demand (COD) (58 %) while readily biodegradable and soluble inert fractions were in the order of 19 % and 3 %, respectively. Full-scale dynamic modeling results successfully confirmed the validity of estimated COD fraction and biodegradation kinetics. End of pipe wastewater reuse potential studied with a pilot plant revealed that almost 100 % soluble inert organics could be concentrated in reverse osmosis (RO) reject. Expectedly, the concentration was far above the COD discharge limit of 200 mg/L. Subsequently, the application of specific ozone dose around 7 kg O3/(kg COD·hour) on RO concentrates was not sufficient to secure the discharge limit by itself. However, the ozone oxidation converted 85 % of inert COD into the (soluble) slowly biodegradable organic matter. The modeling studies also showed that biodegradable organic matter generated by ozonation has much lower degradation kinetics compared to mainstream sequencing batch reactor system.