Volumetric Loading Rate Research Articles

Start-up of a full-scale two-stage partial nitritation/anammox (PN/A) process treating reject water from high solid anaerobic sludge digestion (HSAD)

High solid anaerobic digestion (HSAD) achieves the benefits of high volumetric loading rates and lower reject water production, which, however, results in much more concentrated reject water with a remarkable increase in organics and nitrogen compared with that from conventional AD with low solid content. The high concentrations of ammonium (2000–3500 mg/L) and COD (3000–4000 mg/L) were reported to exert inhibition on anammox bacteria (AnAOB), posing challenges to the application of the partial nitritation/anammox (PN/A). To date, no cases of PN/A process start-up for sludge HSAD reject water were reported. This study demonstrated the start-up process of a 480 m3/d PN/A project without anammox sludge inoculation and treating HSAD reject water from a centralized dewatered sludge treatment plant. The project did not construct new infrastructures but utilized previously constructed tanks to upgrade the process from existing short-cut nitrification-denitrification to a two-stage PN/A process. Although no external anammox sludge inoculation was performed to save seeding sludge cost, the start-up was successfully achieved in about 9 months (273 days) based on a three-step method of “AnAOB enrichment - sludge acclimation - capacity doubling”. During start-up, the relative abundance of AnAOB (Candidatus_Kuenenia) increased from near zero to 12.0%. After start-up, the total inorganic nitrogen (TIN) removal load reached 0.74 kgN/(m3•d), with a total nitrogen removal efficiency of over 90%. Compared to the traditional nitrification-denitrification process, the PN/A process remarkably reduces the addition of organic chemicals and aeration energy consumption, saving approximately 4.2 million yuan (RMB) in operational costs annually. In summary, this research provides a full-scale reference for the start-up of the PN/A process treating sludge HSAD reject water.

Increased oxygen partial pressure enhances toxicity reduction by membrane aerated biofilm reactor treating oil and gas industrial wastewater

Wastewater produced during oil and gas extraction processes is one of the largest residual water streams. Also known as produced water (PW), it has a complex composition and is typically toxic to aquatic ecosystems. This study explores the use of membrane aerated biofilm reactors (MABR) for biological removal of dissolved organic compounds and associated toxicity. Three different oxygen partial pressures (0.2, 0.6 and 1 bar), the last two mimicking subsea pressures at 20 and 40 m below the sea level, respectively, were tested at three different hydraulic retention times (HRT of 24, 12 and 6 h). Reactors were fed both with onshore and offshore PW. Removal rates for organic carbon increased at decreasing HRT. Highest oxygen partial pressure led to best performance at 6 h HRT (30.1 ± 3.0 g-COD m−2 d−1) when treating onshore PW and at all HRT when treating offshore PW, with highest COD removal rate still at 6 h HRT (9.4 ± 1 g-COD m−2 d−1). Removal efficiencies ranged from 78 % when treating onshore PW at 24 h HRT to 36–49 % when treating offshore PW at 6 h HRT. All treatments led to a reduction in toxicity (>92 % reduction for offshore PW), with 0.2 bar oxygen partial pressure showing worst performance, while 0.6 and 1 bar did not show significant differences. The biofilms were dominated by hydrocarbonoclastic, responsible of hydrocarbons biodegradation, and sulfur cycling bacteria. Overall, MABR were effective treating PW and operating at higher oxygen partial pressures yield to better performance, especially at high volumetric loading rates.

Differences on carboxylic acids bioproduction from soluble carbohydrates or proteins in a sequencing batch reactor: Deciphering the influence of the volumetric and specific organic loading rate

Acidogenic fermentation (AF) has been extensively explored. However, the impact of operational parameters on AF has led to inconsistent results. In this work, AF experiments were performed in a sequencing batch reactor (SBR) using simulated wastewaters solely containing soluble carbohydrates or proteins as carbon sources to independently assess the impact of the volumetric organic loading rate (OLRv) and of the specific organic loading rate (OLRs). When only carbohydrates were used, the main effluent components were acetic and butyric acids at OLRv of 6.0 g COD L−1 d−1, while changing OLRv over 11.0 g COD L−1 d−1 gave acetic acid and ethanol as main components. Conversely, if the carbon source consisted solely of proteins, increasing the OLRv or the OLRs had minimal impact on the AF performance and on the effluent composition. Also, in the case of carbohydrate experiments, increasing the OLRs from 2.3 to 3.8 g COD g−1 VSS d−1 promoted chain elongation reactions, as caproic acid formation was also observed. Besides, at the highest OLRv tested in this work for protein experiments (18.5 g COD L−1 d−1), it was obtained the maximum isocaproic acid concentration using mixed microbial cultures and without adding any external electron donor. The SBR configuration proved to be an adequate system, especially when proteins were used as carbon source, since it makes possible to keep low the OLRs and to reduce the hydrolysis limitations. Finally, the bacterial genera detected in the reactors notably changed between both substrates. Future work must be focused on identifying carboxylic acid producing-genera from proteins.

Olive oil waste treatment: A review

The most intriguing results were obtained on UASB reactors, both at laboratory and pilot scale, fed on diluted waste, and the most promising results were obtained on UASB reactors, both at laboratory and pilot scale, fed on diluted waste. With these digesters, volumetric loading rates were observed and 70 percent removal efficiency was achieved. The start-up of UASB reactors fed with waste from olive oil mills is a complicated process that must be carefully monitored and optimized. Starting with very diluted trash yielded the greatest results. Granulation of the sludge, as seen in UASB digesters fed on sugar beet wastewaters, was not attained; however, the sludge's settleability was observed to be excellent. Since the olive oil industry has been blamed for a lot of pollution, there has been a lot of pressure to improve olive oil waste treatment facilities. Bioremediation (ex-situ, in-situ), thermal processes (incineration, pyrolysis, gasification), evaporation, membrane processes, electrolysis, ozonation, digestion, Coagulation/flocculation/precipitation, and distillation are among the many methods currently in use. Per the waste treatment approach, both advantages and downsides were described, along with the methodology and explicit flow diagrams. Furthermore, the most recent studies were provided, with around twenty–five figures primarily illustrating the efficacy of current waste treatment procedures versus time or temperature. The comparison of the various olive oil waste treatment approaches revealed that, while bioremediation is the most environmentally beneficial option, it is not the only one.

Performance evaluation of ICX reactor in treatment of paper mill wastewater: a case study in South Vietnam.

This study evaluates the performance of the Internal Circulation eXperience (ICX) reactor in treating high-strength paper mill wastewater in the south of Vietnam. The ICX reactor effectively managed organic concentrations (sCOD) of up to 11,800 mg/L. Results indicate a volumetric loading rate (VLR) of 26.8 kg/m3 × day, achieving processing efficiency exceeding 81% while consistently maintaining volatile fatty acids (VFA) below 300 mg/L. The study employed Monod and Stover-Kincannon kinetic modeling, revealing dynamic parameters including Ks = 56.81 kg/m3, Y = 0.121 kgVSS/kgsCOD, Kd = 0.0242 1/day, μmax = 0.372 1/day, Umax = 151 kg/m3 × day, and KB = 175.92 kg/m3 × day, underscoring the ICX reactor's superior efficiency compared to alternative technologies. Notably, the reactor's heightened sensitivity to VFA levels necessitates influent concentrations below 1,400 mg/L for effective sludge treatment. Furthermore, the influence of calcium on treatment efficiency requires post-treatment alkalinity maintenance below 19 meq/L to stabilize MLVSS/MLSS concentration. Biogas production ranged from 0.6 to 0.7 Nm3 biogas/kg sCOD; however, calcium impact diminished this ratio, reducing overall treatment efficiency and biogas production. The study contributes valuable insights into anaerobic treatment processes for complex industrial wastewaters, emphasizing the significance of controlling VFA, calcium, and alkalinity for optimal system performance.

Dynamic and structural response of a multispecies biofilm to environmental perturbations induced by the continuous increase of benzimidazole fungicides in a permeable reactive biobarrier.

This work explores the dynamics of spatiotemporal changes in the taxonomic structure of biofilms and the degradation kinetics of three imidazole group compounds: carbendazim (CBZ), methyl thiophanate (MT), and benomyl (BN) by a multispecies microbial community attached to a fixed bed horizontal tubular reactor (HTR). This bioreactor mimics a permeable reactive biobarrier, which helps prevent the contamination of water bodies by pesticides in agricultural wastewater. To rapidly quantify the microbial response to crescent loading rates of benzimidazole compounds, a gradient system was used to transiently raise the fungicide volumetric loading rates, measuring the structural and functional dynamics response of a microbial community in terms of the volumetric removal rates of the HTR entering pollutants. The loading rate gradient of benzimidazole compounds severely impacts the spatiotemporal taxonomic structure of the HTR biofilm-forming microbial community. Notable differences with the original structure in HTR stable conditions can be noted after three historical contingencies (CBZ, MT, and BN gradient loading rates). It was evidenced that the microbial community did not return to the composition prior to environmental disturbances; however, the functional similarity of microbial communities after steady state reestablishment was observed. The usefulness of the method of gradual delivery of potentially toxic agents for a microbial community immobilized in a tubular biofilm reactor was shown since its functional and structural dynamics were quickly evaluated in response to fungicide composition and concentration changes. The rapid adjustment of the contaminants' removal rates indicates that even with changes in the taxonomic structure of a microbial community, its functional redundancy favors its adjustment to gradual environmental disturbances.

Reactivation performance and sludge transformation after long-term storage of Partial denitrification/Anammox (PD/A) process

This study explores the startup of innovative Partial denitrification/Anammox (PD/A) process using long-term stored sludge (>2 years at 4 °C). Results indicate a swift recovery performance, characterized by a progressive increase in the activity of functional microorganisms with improved nitrogen volumetric loading rate during operation. Stable nitrogen removal efficiency of 99.6 % was attained at 14.2 °C under influent nitrate and ammonium of 120 and 100 mg/L, respectively. A distinctive transformation was observed as the initially black seeding sludge transitioned to brownish-red, accompanied by rapid sludge granulation with size notably increased from 263.1 μm (day 4) to 1255.0 μm (day 128), significantly contributing to the rapid PD/A performance recovery. Microbial community analysis revealed substantial increases in functional bacteria, Thauera (0.09 %–10.4 %) and Candidatus Brocadia (0.003 %–1.98 %), coinciding with enhanced nitrogen removal performance. Overall, this study underscores the viability of long-term stored PD/A sludge as a seed for rapid reactor startup, offering useful technical support to advance practical PD/A process implementation.

Recurrent multi-stressor floc treatments with sulphide and free ammonia enabled mainstream partial nitritation/anammox

Selective suppression of nitrite-oxidising bacteria (NOB) over aerobic and anoxic ammonium-oxidising bacteria (AerAOB and AnAOB) remains a major challenge for mainstream partial nitritation/anammox implementation, a resource-efficient nitrogen removal pathway. A unique multi-stressor floc treatment was therefore designed and validated for the first time under lab-scale conditions while staying true to full-scale design principles. Two hybrid (suspended + biofilm growth) reactors were operated continuously at 20.2 ± 0.6 °C. Recurrent multi-stressor floc treatments were applied, consisting of a sulphide-spiked deoxygenated starvation followed by a free ammonia shock. A good microbial activity balance with high AnAOB (71 ± 21 mg N L−1 d−1) and low NOB (4 ± 17 % of AerAOB) activity was achieved by combining multiple operational strategies: recurrent multi-stressor floc treatments, hybrid sludge (flocs & biofilm), short floc age control, intermittent aeration, and residual ammonium control. The multi-stressor treatment was shown to be the most important control tool and should be continuously applied to maintain this balance. Excessive NOB growth on the biofilm was avoided despite only treating the flocs to safeguard the AnAOB activity on the biofilm. Additionally, no signs of NOB adaptation were observed over 142 days. Elevated effluent ammonium concentrations (25 ± 6 mg N L−1) limited the TN removal efficiency to 39 ± 9 %, complicating a future full-scale implementation. Operating at higher sludge concentrations or reducing the volumetric loading rate could overcome this issue. The obtained results ease the implementation of mainstream PN/A by providing and additional control tool to steer the microbial activity with the multi-stressor treatment, thus advancing the concept of energy neutrality in sewage treatment plants.

Inhibitory impact of the anticancer drug doxorubicin on anaerobic microbial community

The inhibitory effect of the anticancer drug doxorubicin (DOX) on biogas production was evaluated in short-term and long-term exposure assays. The short-term assays reached the DOX IC50 value on 648 ± 50 µg·L−1. In addition, it was found that inhibition caused by the exposure of 10×103 µg·L−1 was reversible after removing DOX from the feeding synthetic medium. Furthermore, DOX can be rapidly sorbed by the biomass (despite the low Kow), which might contribute to the inhibitory effect. The results of long-term exposure assays, when the DOX volumetric loading rate was increased from 100 µgDOX·L−1·day−1 to 200 µgDOX·L−1·day−1, showed that biogas production and COD removal decreased rapidly. However, the methanogenic Archaeas could recover from this exposure, corroborating the results on short-term exposure assays. In conclusion, DOX can play a key role in inhibiting biological wastewater treatment processes if its concentration in hospital wastewater treatment plants increases abruptly.

Abundance and composition of anthropogenic macrolitter and natural debris in road runoff in Ohio, USA

Urban stormwater conveys dissolved pollutants, micropollutants, particulate matter, natural debris, and anthropogenic macrodebris to receiving waters. Though it is widely recognized that anthropogenic macrodebris mobilized by stormwater contributes to global pollution management issues (e.g., ocean garbage patches), these materials often are not the focus of stormwater sampling campaigns. Furthermore, macrodebris can cause clogging of sewer systems, exacerbating flooding and public health hazards. Due to their engineered structures draining directly connected impervious areas (e.g., catch basins, inlets, and pipes), roads present a unique opportunity to mitigate the conveyance of macrodebris in stormwater. To optimize control measures, data are needed to understand expected volume and mass of macrodebris in road runoff. To address this gap in knowledge, a field monitoring study was conducted in Ohio (USA) to quantify the mass, volume, and moisture content of macrodebris transported by road runoff. Designed to filter macrodebris (i.e., material with diameter greater than 5 mm) while maintaining drainage, purpose-built inserts were deployed in catch basins at eleven geographically diverse locations across the state. Macrodebris samples were collected from the inserts every 11.6 days (mean) over a two-year monitoring period. Volume and mass of total and categorical (i.e., vegetation, cigarettes, plastic, glass, metal, wood, fabric, gravel, and paper) debris were characterized. Mean total macrodebris volume and mass were 4.62 L and 0.49 kg per sampling window, corresponding to mean volumetric and mass loading rates of 8.56 L/ha/day and 0.79 kg/ha/day, respectively. Natural debris (e.g., vegetation) was the primary contributor to macrodebris (mean 80.3% (i.e., 3.94 L of the mean 4.66 L total sample volume) and 79.7% (i.e., 0.42 kg of the mean 0.53 kg total sample mass) of total volume and mass, respectively), and exhibited seasonal peaks in autumn due to leaf drop. Road functional class (i.e., interstate, principal arterial, and minor arterial routes), land use, and development density significantly impacted macrodebris generation, with increased total and categorical macrodebris along urbanized interstate highways near commercial and residential areas. Macrodebris moisture content was highly variable (ranging from 1.5 to 440%; mean 78.5%), indicating additional management (e.g., drying, solidification) may be required prior to landfilling. Results of this study inform macrodebris mitigation strategies and required maintenance frequencies for pre-treatment devices for other stormwater control measures treating road runoff, including catch basin inserts and hydrodynamic separators, among others.

Partial nitritation and nitrogen removal of vacuum toilet wastewater from high-speed trains in a sequential batch reactor

Owing to the high contents of organics and nitrogen in vacuum toilet wastewater (VTW) generated from high-speed trains, onsite pretreatment is usually required before VTW can be discharged into municipal sewers. In this study, a partial nitritation process was stably established in a sequential batch reactor to efficiently utilize the organics in synthetic and real VTWs for nitrogen removal and to produce an effluent suitable for anaerobic ammonia oxidation. In spite of the high fluctuations of COD and nitrogen in VTW, the organics used for nitrogen removal stabilized at 1.97 ± 0.18 mg COD mg N−1 removed, and the effluent NO2−-N/NH4+-N ratios were maintained at 1.26 ± 0.13. The removal efficiencies of nitrogen and COD were 31.8 ± 3.5% and 65.2 ± 5.3% under the volumetric loading rates of 1.14 ± 0.15 kg N m−3 d−1 and 1.03 ± 0.26 kg COD m−3 d−1 for real VTW, respectively. Microbial community analysis revealed that Nitrosomonas (0.95%–1.71%) was the dominant autotrophic ammonium-oxidizing bacterial genus, but nitrite-oxidizing bacteria, Nitrolancea, was severely inhibited, with a relative abundance less than 0.05%. The relative abundance of denitrifying bacteria increased by 7.34% when the influent was switched to real VTW. Functional profile predictions of the biomass showed that the decrease in the COD/N ratio and the switch of reactor influent from synthetic to real VTW increased the relative abundance of enzymes and modules involved in carbon and nitrogen metabolisms.

Optimization of Aeration Diffuser System Design: A Simulation Study

The influence of aeration diffuser system design on electricity usage, effluent water quality, and life-cycle cost in biological wastewater treatment was investigated. A plant-wide model was implemented, and simulations were carried out with different process configurations and aeration systems. Model-aided design of new aeration diffuser systems could significantly decrease electricity usage and life-cycle cost while at the same time avoiding negative effects on the treatment performance. The optimum distribution of diffuser systems in tanks in series was found to be influenced by process configuration, volumetric loading rate, temperature, and the internal recirculation flow rate. Compared with a conventional design approach, increasing the number of diffusers, up to a critical point, led to higher energy efficiency and lower life-cycle cost. This was despite an increasing limitation of the minimum airflow rate, leading to dissolved oxygen levels significantly exceeding control targets. Aeration systems optimized by simulations were found to, independently of process configuration, exhibit 20% lower electricity usage and 16%–18% lower life-cycle costs compared with systems designed based on a more conventional approach typically applied in practice.

Modeling of a capillary microbioreactor for VOC removal

Capillary microreactors have shown superior performance as a result of the precise control of reaction parameters, contact time, shape and size of the interface between gas and liquid and enhanced mass transfer due to high surface to volume ratio. In this work, a mathematical model of a capillary microbioreactor treating VOC vapors was developed and validated experimentally. The main goal for this conceptual model was to adequately describe or predict VOC vapor removal in the capillary microbioreactor under different operating conditions and its mineralization to CO2. The model considered toluene as the model VOC and included oxygen consumption and carbon dioxide production. Experimental data used for model calibration and validation were obtained from experiments conducted at various toluene and volumetric loading rates. A parametric sensitivity to the model was performed to identify the parameters that most affected the performance of the microbioreactor system. The most sensitive parameters were biokinetic parameters followed by system specific parameters, indicating that the system performance was limited by kinetics rather than by mass transfer. Overall, the model and the approach described herein help us better understand the performance and limits of these microbioreactors and they serve as important tools for process optimization.

Effects of ciprofloxacin on biogas production and microbial community composition in anaerobic digestion of swine wastewater in ASBR type reactor

ABSTRACT In swine farming, antibiotics are often used to reduce disease and promote animal growth. Part of these compounds is not absorbed by the swine body, being excreted and later reaching the treatment systems, soil, and nearby waterbodies. This research sought to investigate the influence of adding ciprofloxacin (CIP) on the anaerobic digestion of swine wastewater. For that, a bench-scale anaerobic sequential batch reactor (ASBR) was used, with 5 L of working volume in six different phases, with volumetric organic loading rate (VOLR) and CIP dosage variation. According to the results, the optimal VOLR for the reactor was 0.60 ± 0.11 gSV L−1 d−1, resulting in biogas productivity of 0.51 ± 0.03 Lbiogas L−1 d−1. After initial stability, adding substrate with 0.5 mgCIP L−1 resulted in an abrupt drop of 82% in the productivity from the 7th to 11th day of addition, coinciding with volatile acids accumulation. Afterward, the reactor recovered and reached apparent stability, with productivity similar to the previous step without the drug. For 2.5 mgCIP L−1 in the substrate, the biogas productivity at equilibrium was 11.8% lower than in the phases with the same VOLR and 0.0 and 0.5 mgCIP L−1. Organic matter removals near 80% were achieved for both dosages. The 16S rRNA metagenomic analyses showed an increase in the relative abundance of most of the phyla found, indicating that the dosages used allowed the acclimatization of microorganisms and possibly the compound biodegradation.

Upgrading ADM1 by Addition of Lag Phase Sub-model to Simulate Acidic Inhibition of Methanogenic Reactor

This study is aimed at improving calculation quality for IWA Anaerobic Digestion Model No.1 (ADM1) to simulate acidic failure of the methane fermentation systems and its performance recovery. The methanogen collected from digestate at a municipal wastewater treatment plant was cultivated in a lab-scale continuous reactor receiving acetate as a sole organic source. By varying the influent concentration during 400 days of operation, 6 datasets of acidification events were obtained to simulate the concentrations of acetate, VSS, pH, and the methane production rate. The ADM1 equipped with either pH sub-model or undissociated acetate sub-model could reproduce the deterioration of reactor performance in the acidic failure but totally failed to simulate the recovery in the subsequent lowered volumetric loading rate. The statistical analysis revealed both ADM1 models had relatively low correlation coefficient (Nash-Sutcliffe model efficiency coefficient (NSE)) of 0.31–0.38 although these were considerably improved from that without parameter calibration (NSE = −0.04). To cope with the mismatch, a lag phase sub-model was developed. The sub-model is composed of the remaining relative activity of the microorganism at which the inhibition peaked, and the half-saturation coefficient to express the specific length of lag phase. By adding the sub-model into the calibrated ADM1, NSE was significantly improved to 0.49–0.53.

Nitrification resistance and functional redundancy maintain the system stability of partial nitrification in high-strength ammonium wastewater system

The sudden change of ammonia loading in high-strength ammonium wastewater treatment can directly affect the system stability by altering microbial community dynamics. To maintain the system stability, the effects of ammonia shock loading on microbial community dynamics must be studied. Two sets of sequencing batch reactors were operated with 6 shock cycles (maximum volumetric loading rate of 1928 mg N/(L·d)). CN system contained both organic carbon and ammonia and N system contained only ammonia. Comparing with N system, CN system operated more stably and had higher nitrite accumulation rate. Free ammonia (FA) was the select stress for the turnover of CN microbial communities, while the N communities didn t shift much. The increase of Nitrosomonas and the appearance of heterotrophic nitrification-aerobic denitrification bacteria in CN system presented its resistance and redundancy against FA impact, while the increase of functional genes exhibited functional genes redundancy which maintained the system stability.

Integrated selection of PHA-storing biomass and nitrogen removal via nitrite from sludge reject water: a mathematical model

ABSTRACT One of the most recent innovations to promote a circular economy during wastewater treatment is the production of biopolymers. It has recently been demonstrated that it is possible to integrate the production of biopolymers in the form of polyhydroxyalkanoates (PHA) with nitrogen removal via nitrite during the treatment of sludge reject water. In the present study, simulation of a new process for bioresource recovery was conducted by an appropriate modification of the Activated Sludge Model 3. The process consists of the integrated nitrogen removal via nitrite from sludge reject water and the selection of PHA-storing biomass by inducing a feast and famine regime under aerobic and anoxic conditions. According to the results, it is anticipated that simulation data matched very satisfactorily with the experimental data and confirmed the main experimental observation, showing that during the famine period the PHA depletion was almost complete due to the availability of nitrite as the electron acceptor. Simulation results indicate that the selection of the volumetric organic loading rate and of the relative duration of the aerobic feast/anoxic famine duration is critical in order to allow for the effective denitritation of the internally stored PHA during the famine phase.

Removal of methanol vapors in a jet-loop bioscrubber equipped with a venturi injector

A jet loop reactor equipped with a Venturi injector was used as a bioscrubber to treat air polluted with methanol. The oxygen transfer coefficient of the reactor was first characterized under abiotic conditions at different volumetric power inputs, ionic strengths and dynamic viscosities. The oxygen transfer coefficient (KLa) ranged 46.9–1272.82 h−1 with an actual volumetric power inputs from 3.6 to 21.5 kW m−3. Then, the reactor was inoculated with a mixed culture and applied for the treatment of air artificially polluted by methanol. Over 91 days, the actual volumetric power input was maintained at 11 kW m−3 and the KLa ranged from 720 to 860 h−1, while the volumetric loading rate was increased from of 5–60 g L−1 d−1 and the hydraulic residence time was increased from of 12–96 h. The volumetric methanol removal rate reached a maximum of 40.75 g L−1 d−1, at a removal efficiency of 67.6%. Under the optimal conditions tested, the microbial growth yield reached a minimum value of 0.11 g COD g−1 COD. These results suggest that high efficiency reactors such as the Venturi jet loop tested in the present work allow to reach high volumetric removal rates while maintaining low growth yield.

Sequencing Batch Reactor Performance Evaluation on Orthophosphates and COD Removal from Brewery Wastewater

The discharge of industrial effluent constituting high orthophosphates and organic pollutants in water receiving bodies compromises freshwater quality and perpetuates eutrophication. In this study, an anaerobic–aerobic sequencing batch reactor (SBR) under activated sludge was investigated for orthophosphates and chemical oxygen demand (COD) removal from brewery wastewater. Raw brewery wastewater samples were collected on a daily basis for a period of 4 weeks. The findings of the study are reported based on overall removal efficiencies recording 69% for orthophosphates and 54% for total COD for a sludge retention time (SRT) of 7 days and hydraulic retention time of 18 h at mesophilic temperature conditions of ±25 °C. Moreover, the SBR system showed stability on orthophosphate removal at a SRT ranging from 3 to 7 days with a variation in organic volumetric loading rate ranging from 1.14 to 4.83 kg COD/m3.day. The anaerobic reaction period was experimentally found to be 4 h with the aerobic phase lasting for 14 h. The SBR system demonstrated feasibility on orthophosphates and COD removal with variation in organic loading rate.

Evaluation of a sulfidogenic system fed with microalgal biomass of Chlorella pyrenoidosa as an electron donor: Sulfate reduction kinetics

In this study, a sulfidogenic reactor fed with microalgal biomass of Chlorella pyrenoidosa as an electron donor was operated in a continuous mode. This study evaluated the influence of various initial sulfate concentration from 1.0 to 2.5 g/L on anaerobic sulfate reduction kinetics by a sulfidogenic enrichment culture predominantly Desulfovibrio sp. VSV2. It was observed that volumetric sulfate reduction rate (VSRR) was consistently increasing with an increase in volumetric sulfate loading rate (VSLR) across the retention time of 7–10 days. For a retention time of 7 days, the maximum VSRR was noted as 0.0050 g/(L.h) with a corresponding VSLR of 0.0089 g/(L.h). When retention time was maintained for 10 days, a maximum sulfate reduction of 65% and a maximum bacterial concentration of 1.632 g/L were achieved for an initial sulfate concentration of 1.5 g/L. It was concluded that VSLR facilitated through both dilution rate and initial sulfate concentration had a significant influence over sulfate reduction kinetics. The results of the study suggested that the microalgal-fed sulfidogenic system could be effectively employed for reduction of sulfate from sulfate-rich wastewater.