Biological COD Research Articles

The importance of the electron acceptor: Comparison between flooded and tidal bioelectrochemical systems for wastewater treatment and nutrients enriched solution production

In this study, a new bioelectrochemical system (BES) with an alternative setup of microbial fuel cell (MFC) is proposed: an additional cathodic collecting chamber is added to the air-exposed cathode to allow the recovery of the cations migrating from the anodic chamber. Up to 60 % of inorganic nutrients and 85 % of COD were removed from wastewater (WW). In the cathodic chamber, recovered nutrients partitioned differently depending on their solubility: P, Mg and Ca were predominantly found in precipitates as insoluble salts, while Na and K in the cathodic solution. N was recovered from the cathodic chamber as ammonia (NH3) (22 %) and as precipitate while deposited on the cathode as salts (15 %). Flooded versus tidal operation modes were further compared to achieve the best oxygen (strong electron acceptors) supply in the anodic chamber to increase biological COD degradation and nutrients migration towards the cathodic chamber.

Performance appraisal of microbial inoculants treating polluted surface water through bench‐scale investigation

AbstractBACKGROUNDThis study investigates the performance of microbial inoculants by exploring pollutant removal efficiency, microbial viability and substrate removal kinetics for treating polluted surface water. The morphological, elemental composition and biochemical characterization of inoculants were analyzed using field emission scanning electron microscopy with energy dispersive X‐ray spectroscopy (FESEM‐EDX) and Fourier transform infrared (FTIR) techniques. The identification of bacterial strains in polluted feed water also was performed using 16S rRNA partial sequencing. Bench‐scale efficacy of selected microbial inoculants (MI) along with control for each study was performed at variable retention times ranging from 6 to 72 h, under optimum operating conditions.RESULTSThe maximum removal (86% and 90%) of the organic load (chemical and biological oxygen demand, COD and BOD) was achieved by inoculants containing Bacillus subtilis along with other microbial species after 72 h of treatment. The microbial inoculant MI‐2 containing Paracoccus pantotrophus and Pseudomonas Putida exhibited the highest TN removal (66%) after 72 h of contact time. Adenosine triphosphate (ATP) analysis revealed that the active biomass ratio is a more precise indicator of healthy biomass instead of the conventionally used parameter MLVSS (mix liquor volatile suspended solids) in a biological treatment system, which apparently provides a significant addition to the existing knowledge base for the operational wastewater treatment plants (WTPs).CONCLUSIONIn this study, microbial inoculants were found to be frugal and viable treatment tools for the remediation of polluted surface water. Exploiting such inoculants also can overcome the inefficiencies of existing sewage treatment plants by serving as potential tools for bio‐augmenting the indigenous microbial fingerprint of aeration tank/secondary treatment systems. © 2023 Society of Chemical Industry (SCI).

Achieving simultaneous biological COD and phosphorus removal in a continuous anaerobic/aerobic A-stage system

Recovering energy from wastewater in addition to its treatment is a hot trend in the new concept of water resource recovery facility (WRRF). High-rate systems operating at low solid retention time (SRT) have been proposed to meet this challenge. In this paper, the integration of Enhanced Biological Phosphorus Removal (EBPR) in an anaerobic/aerobic continuous high-rate system (A-stage EBPR) was evaluated. Successful P and COD removal were obtained operating at SRT 6, 5 and 4 days treating real wastewater, while a further decrease to 3 days led to biomass washout. The best steady state operational conditions were obtained at SRT = 4d, with high removal percentage of P (94.5%) and COD (96.3%), and without detecting nitrification. COD mineralization could be reduced to 30%, while 64 % of the entering carbon could be diverted as biomass to energy recovery. Regarding nitrogen, about 69±1% of the influent N was left as ammonium in the effluent, with 30% used for biomass growth. The aerobic reactor could be operated at low dissolved oxygen (DO) (0.5 mg/L), which is beneficial to decrease energy requirements. Biochemical methane potential (BMP) tests showed better productivity for the anaerobic sludge than the aerobic sludge, with an optimal BMP of 296±2 mL CH4/gVSS. FISH analysis at SRT = 4d revealed a high abundance of Accumulibacter (33±13%) and lower proportion of GAO: Competibacter (3.0±0.3%), Defluviicoccus I (0.6±0.1%) and Defluviicoccus II (4.3±1.1%).

Treatment of Agricultural Wastewater with Chlorpyrifos by Coupling of Heterogeneous Photocatalysis and Anaerobic Biological Process

Treatment of wastewater with Chlorpyrifos content using heterogeneous photocatalysis was evaluated, for which a compound parabolic collector (CPC) was used, under different combinations of pH and TiO2 concentration designed using the response surface methodology (RSM), and an anaerobic biological process based on the specific methanogenic activity test (SMA), using a flocculent sludge and an initial concentration of 2.0 g VSS/L. Initially, water resulting from the triple washing of equipment for manual application of Chlorpyrifos from the El Zulia Irrigation District and the municipality of Bucarasica were characterized. In the biological process, COD and TOC removals of 46.4% and 86.6% were obtained; while by applying preliminary photocatalytic processes, under optimal conditions of TiO2 (100 mg/L), pH (3 units) and retention time (3 h), better biodegradability efficiencies (72.2% and 53.0%) were achieved. The results revealed that the combined use of advanced oxidation processes with biological treatment technologies is technically viable, as it increases the efficiency of removing contaminants from agricultural effluents with Chlorpyrifos.

CWWQI on the Evaluation of Effluent Wastewater from Al-Dora Refinery WWTP

This study aimed to evaluate effluent wastewater form Al-Dora refinery wastewater treatment plant (DWWTP). The quality of wastewater for agricultural irrigation was evaluated using Canadian Wastewater Quality Index (CWWQI). Seven physical, chemical and biological parameters, namely, pH, SO4, Cl−, phenol, COD, BOD5 and TDS were analyzed from April 2018 to March 2019. Results of CWWQI referred to variation in the acceptability of the treated wastewater for reuse in crop irrigation. The treated wastewater had CWWQI of 80.19, which reflects good quality. Hence, the treated wastewater was suitable for irrigation of many crops.

Investigation on nitrogen removal performance of an enhanced post-anoxic membrane bioreactor using disintegrated sludge as a carbon source: An experimental study

In this study, a Post-Anoxic Membrane Bioreactor (PA-MBR) has been proposed to enhance nitrogen removal from real domestic wastewater. The system comprised an aeration tank followed by an anoxic chamber in which a membrane module was immersed. For effective proliferation of denitrifiers, acetate in the form of vinegar and later the disintegrated sludge through ultra-sonication were used as the carbon source for denitrification. The main goals of this study were enhancing the biological nitrogen and COD removal and investigating the influential aspects of using disintegrated sludge as a readily biodegradable COD in the PA-MBR system. The fouling behavior of the membrane was also studied as a consequent drawback of membrane application in the anoxic environment, through monitoring the trends of Transmembrane Pressure (TMP) increase over time along with the Scanning Electron Microscopy (SEM) studies. The results showed that the system in its steady-state conditions was able to remove 93.24% and 94.57% of COD and TN contents, respectively. The observed COD, TN, NO3−-N, TSS and turbidity contents of the effluent were equal to 28 ± 4.85 mg/L, 1.69 ± 0.33 mg/L-N, 1.52 ± 0.29 mg/L-N, <1 mg/L and <0.18 NTU, respectively. Furthermore, the membrane demonstrated a consistently superb performance, despite its application in the anoxic environment. Using physical cleaning of the membrane surface by a water jet every two to five days instead of conventional chemically enhanced backflush, the membrane’s chemical cleaning intervals were extended up to five weeks.

The leakage of sewer systems and the impact on the 'black and odorous water bodies' and WWTPs in China.

China has achieved significant progress on wastewater treatment and aquatic environmental protection. However, leakage (in- and exfiltration) of sewer systems is still an issue. By using the statistical data of water and wastewater in 2016 in China, and the person loads (PLs) of water and wastewater in Singapore, the leakage fractions of hydraulic flow, organic carbon (COD), nitrogen (N) and phosphorus (P) mass loading, and in-sewer COD biological removal in the sewer systems of China (except Hong Kong, Macau and Taiwan), Shanghai, Guangzhou and Beijing were reported for the first time. The fractions of hydraulic flow infiltration (13%, Shanghai and Guangzhou) and exfiltration (39%, China) were calculated. Except Beijing, whose sewer networks are under appropriate management with small leakage fractions, the exfiltration fractions of COD (including in-sewer biological COD removal) ranged from 41% (Shanghai) to 66% (China) and averaged 55%; N ranged from 18% (Shanghai) to 48% (China) and averaged 33%; and P ranged from 23% (Shanghai and Guangzhou) to 44% (China) and averaged 30%. The exfiltrated sewage, COD, N and P not only wastes resources, but also contaminates the aquatic environment (especially groundwater) and contributes to 'black and odorous water bodies'. In- and exfiltration in the sewer network leads to low influent COD concentration, C/N ratio and high inorganic solids and inert particulate COD concentrations of many municipal wastewater treatment plants (WWTPs) causing high cost for nutrient removal, poor resource recovery, additional reactor/settler volume requirement and other operational problems. Therefore, tackling sewer leakage is of primary importance to today's environment in China. Recommendations for the inspection of sewer systems and the rehabilitation of damaged sewers as well as the development of design and operation guidelines of municipal WWTPs tailored to the specific local sewage characteristics and other conditions are proposed.

Polytetrafluoroethylene (PTFE) hollow fiber AnMBR performance in the treatment of organic wastewater with varying salinity and membrane cleaning behavior

PTFE hollow fiber anaerobic membrane bio-reactor (AnMBR) performance was investigated in the treatment of organic wastewater, with varying salinity and PTFE membrane cleaning behavior. The AnMBR was operated for 226 days, with a total and biological COD removal efficiency of 97.2% and 89.9% respectively, at a NaCl concentration of 35 g L−1. A high number of Proteobacteria (38.2%) and Bacteroidetes (25.9%) were present in the system, with an increase in membrane fouling rate from 1.88 × 1011 to 2.63 × 1011 m−1 d−1 with higher salinity. The effects of soluble microbial products (SMP), extracellular polymeric substances (EPS), low molecular-weight (LMW) carbohydrates, sludge particle size and inorganic element accumulation, were evaluated on membrane fouling. Flux recovery of fouled PTFE membranes reached 91.6% with offline cleaning. Overall, results indicate that PTFE hollow fiber AnMBR provides a promising method for the treatment of saline organic wastewater.

Validation of a multi-phase plant-wide model for the description of the aeration process in a WWTP

This paper introduces a new mathematical model built under the PC-PWM methodology to describe the aeration process in a full-scale WWTP. This methodology enables a systematic and rigorous incorporation of chemical and physico-chemical transformations into biochemical process models, particularly for the description of liquid-gas transfer to describe the aeration process. The mathematical model constructed is able to reproduce biological COD and nitrogen removal, liquid-gas transfer and chemical reactions. The capability of the model to describe the liquid-gas mass transfer has been tested by comparing simulated and experimental results in a full-scale WWTP. Finally, an exploration by simulation has been undertaken to show the potential of the mathematical model.

Carbon and nutrient biological removal in a University of Cape Town membrane bioreactor: Analysis of a pilot plant operated under two different C/N ratios

The effect of the carbon-to-nitrogen (C/N) ratio variation in a University of Cape Town Membrane bioreactor (UCT-MBR) was investigated. The experimental campaign was divided into two phases, each characterized by a different C/N ratio (namely, 10 and 5, Phase I and Phase II, respectively). The UCT-MBR pilot plant was analysed in terms of carbon and nutrients removal, biomass respiratory activity, activated sludge features and membrane fouling. The results highlighted that the nutrients removal was significantly affected by the decrease of the C/N ratio during the Phase II. The biological carbon removal was also affected by the low C/N value during the Phase II. Indeed, the average biological COD removal efficiency was equal to 72.9% during the Phase II, while the average value was 82.8% in the Phase I. The respirometric batch test suggested that both heterotrophic and autotrophic species were severely affected by the lower C/N ratio in the Phase II. Moreover, a decrease of the membrane filtration properties was observed during the Phase II, mainly due to the worsening of the activated sludge features, which enhanced the increase of SMP production.

A new general methodology for incorporating physico-chemical transformations into multi-phase wastewater treatment process models

This paper introduces a new general methodology for incorporating physico-chemical and chemical transformations into multi-phase wastewater treatment process models in a systematic and rigorous way under a Plant-Wide modelling (PWM) framework. The methodology presented in this paper requires the selection of the relevant biochemical, chemical and physico-chemical transformations taking place and the definition of the mass transport for the co-existing phases. As an example a mathematical model has been constructed to describe a system for biological COD, nitrogen and phosphorus removal, liquid–gas transfer, precipitation processes, and chemical reactions. The capability of the model has been tested by comparing simulated and experimental results for a nutrient removal system with sludge digestion. Finally, a scenario analysis has been undertaken to show the potential of the obtained mathematical model to study phosphorus recovery.

Improvement of Biofilm Carriers for the Treatment of Automotive Industry Wastewater

The efficient biological treatment of the wastewater of the automotive industry is difficult, mainly because of the low biological oxygen demand/chemical oxygen demand (BOD/COD) ratio. Moreover, wastewater of the automobile industry contains heavy metals and other chemical substances that may have toxic effects. Biofilm and hybrid technologies could be optimal solutions for the treatment of such heavily biodegradable wastewater streams. This paper presents the experimental results of the examination of modified biofilm carriers developed for the treatment of the wastewater of the automotive industry. Three modified biofilm carriers were examined: a high-density polyetyilene (HDPE), an HDPE modified with 50% carbon nanotube (CNT) content, and an HDPE modified with 75% CNT content. They were compared to a patented biofilm carrier having similar morphological properties (control). The examination consisted of two parts: (1) studying the colonisation of biofilm on each carrier, and (2) studying the biological COD removal efficiency of biofilm reactors filled with the four different biofilm carriers in 25% volumetric ratio each with an influent industrial emulsion sewage. The obtained results demonstrated that neither the rate of biofilm colonisation, nor the COD removal efficiency show any significant difference comparing the four biofilm carriers. The colonisation of biofilm was appropriate on each carrier and this ensured proper efficiency of COD removal in each biofilm reactor. Based on the results, it can be stated that the suggested advantageous characteristics of CNTs do not appear as it is mixed in the plastic raw material during the production of biofilm carriers. The absence of the significant difference observed between the examined carriers suggests that the production of biofilm carriers from recycled plastic could carry financial advantages compared to the control carrier. Further experiments could specify differences by various hydraulic loads or toxic effects.

하천 수질정화를 위한 실험실 규모 다단식 토양여과 시스템에서 오염물질 제거에 미치는 운전인자의 영향

In this study we investigated the effects of operational parameters of a multi-layered soil filtration (filter depth, filtration velocity, and continuous/intermittent operation) on removal of pollutants in river water. As filter depth increased removal of all the pollutants (COD, TP, TN, and NH4-N) was increased because the increase in filter depth increased in contact time between media and pollutants. The removal of TP and NH4-N more increased with the increase in filter depth, comparing to the biological COD removal which was performed only in the top layer, since the removal mechanism of TP and NH4-N was physicochemical process occurring throughout the whole layers. However, the reduction in filtration velocity resulted in decrease of removal all the pollutants removal due to shorter retention time. Biological COD removal was more influenced with the reduction in filtration velocity (longer retention time), than the removal of TP and NH4-N. Because biological process was occurred only in the top layer which has relatively shorter retention time, comparing with physicochemical process occurred throughout whole media. Therefore, it is desirable that the operation parameters be controlled toward increasing retention time, in order to achieve efficient pollutants removal. The change in operation mode (continuos vs. intermittent operations) did not provide significant effects on the pollutant treatment efficiency by the multi-layered soil filtration system. Our findings suggest that for stable long-term operation it should be considered keeping conditions for biological activity and accelerating clogging.

Integration of a Coagulation/Flocculation step in a biological sequencing batch reactor for COD and nitrogen removal of supernatant of anaerobically digested piggery wastewater

The supernatant from mesophilic anaerobic digestion of piggery wastewater is characterised by a high amount of COD (4.1 g COD L −1), ammonium (2.3 g NH 4 + – N L - 1 ) and suspended solids (2.5 g SS L −1). This effluent can be efficiently treated by means of a Sequencing Batch Reactor (SBR) strategy for biological COD, SS and nitrogen removal including a Coagulation/Flocculation step. Total COD and SS reduction yields higher than 66% and 74%, respectively, and a total nitrogen removal (via nitrite) of more than 98% were reached when working with HRT 2.7 days, SRT 12 days, temperature 32 °C, three aerobic/anoxic periods, without external control of pH and under limited aeration flow. The inhibition of nitrite oxidizing biomass was achieved by the working free ammonia concentration and the restricted air supply (dissolved oxygen concentration below 1 mg O 2 L −1). Since a part of the total COD was colloidal and/or refractory, a Coagulation/Flocculation step was implemented inside the SBR operating strategy to meet a suitable effluent quality to be discharged. Several Jar-Tests demonstrated that the optimal concentration of FeCl 3 was 800 mg L −1. A respirometric assay showed that this coagulant dosage did not affect the biological activity of nitrifying/denitrifying biomass.

Response of the zoobenthos community along the dispersion plume of a highly polluted stream in the receiving waters of a large river (Rio de la Plata, Argentina)

The ingress of an urban stream carrying high contaminant loads into a large coastal river originates a “dispersion plume” subject to the hydrological conditions of a river affected by tidal influences. In the present study 21 sites within the “contaminant plume” of the Riachuelo River in the Rio de la Plata were analysed on the same date in order to evaluate the biological status of the area which receives this strong environmental impact, and to examine its effect on the zoobenthic communities. Diversity, taxonomic richness, abundance, physico-chemical parameters and a biological index (IMRP) were used to assess the responses of the macroinvertebrates. The correlation between exposure and effect was calculated by means of the exposure index (IEX). The relationship between the macroinvertebrate communities and environmental variables was examined using CCA analysis. Conductivity, Cr, BOD and COD, were most strongly correlated with Axis 1, suggesting the existence of a gradient of environmental degradation. The most severely contaminated sites (IMRP= 1.1–2.5; IEX = 100–78%) were all characterized by a reduced community dominated by Nematoda and Oligochaeta. A moderate response was observed between 1400 and 1600 m from the coast (IMRP = 2.6–3.9; IEX = 36%) largely owing to the physico-chemical characteristics of the recipient river which contributed to moderating the effect of the anthopogenic perturbation. For statistical validation, this area was compared with historical physico-chemical and biological data, where OD and COD showed the same tendency throughout the 10-year period.

Limitations of ASM1 and ASM3: a comparison based on batch oxygen uptake rate profiles from different full-scale wastewater treatment plants

The two most popular models for the description of the biological COD removal are ASM1 and ASM3. However, some numerical inconsistencies arise when using these models to interpret the data obtained in short-term respirometric batch experiments. In this study, both models are fitted to four different respirometric batch profiles obtained with biomass from different WWTP. The parameter estimation results and the practical (local) identifiability are analysed, and the limitations of both models are discussed. The growth yield obtained by fitting ASM1 to the short-term respirometric batch profiles is higher than the default one, as well as the storage yield obtained by fitting ASM3 is lower than the default one. Based on these values, possible improvements to the modelling of the biological COD removal, such as the inclusion of simultaneous growth and storage on external substrate, are proposed.

Innovative energy interaction with a waste incineration plant leads to advanced biological P- and COD-removal and costs reduction of the extension of Nijmegen wastewater treatment plant

The extension of the Nijmegen wastewater treatment plant for full nitrogen and phosphorus removal is enormously reduced by introducing an innovative energy interaction with an incineration plant. A reduction of the investment costs of 30-40% has been reached. Heating up a part of the primary sedimentation overflow leads to a constant process temperature of 20-25 degrees C and an advanced biological phosphorus and COD removal.

Integrated aerobic biological treatment and chemical oxidation with Fenton’s reagent for the processing of green table olive wastewater

Table olive processing wastewater (TOPW) is unsuitable for disposal at municipal or industrial wastewater treatment plants due to its high organic and phenol content. Aerobic biological treatment using an Aspergillus niger strain in a bubble column bioreactor in combination with chemical oxidation was studied for the management of TOPW to a quality which corresponds to the input standards for wastewater treatment plants (COD<1200 ppm, BOD<500 ppm). After 2 days of biological treatment COD was reduced by 70%, while the total and simple phenolic compounds were decreased by 41 and 85%, respectively. In the chemical treatment step, the effect of different H 2O 2 concentrations on the patterns of COD and phenol reduction was studied. The main effect of the chemical oxidation step was the elimination of persistent phenolic compounds during the biological treatment of total phenolic compounds. Coagulation with CaO significantly improved the efficiency of the process.

Biodegradability assessment of ozonated raw and biotreated pharmaceutical wastewater.

The activated sludge specific oxygen uptake rate (SOUR) and BOD(5)/COD ratios of biologically pretreated pharmaceutical wastewater were analyzed and compared to assess relative changes in biotreatability during ozonation at a rate of 7.4 g/(L x h) for 4 h. An appreciable COD removal (41%) was achieved by the initial biological treatment process, whereas ozonation was more effective in reducing the UV-sensitive aromatic compounds present in the pretreated effluent. Sequential treatment using activated sludge + ozonation processes resulted in an average COD removal efficiency of 48%, and a proceeding biotreatment stage increased the overall COD removal to 53%. An optimum ozone dose in the range of 1,854-3,708 mg/L corresponding to a specific ozone input rate of 0.23-0.46 mg O(3)/mg COD(o) existed where SOUR (3.7 x 10(-3) mg O(2)/[mg MLSS x min] for ozonation at pH 8) and BOD(5)/COD (0.57) as well as the proceeding biological COD removal yield Y(COD) (average 8 mg COD/mg MLSS) exerted maximum values.

Treatment of spent process water from a fruit juice company for purposes of reuse: hybrid process concept and on-site test operation of a pilot plant

In order to treat spent process water from companies of the food and beverage industries up to drinking water quality, a process concept was developed consisting of the following two treatment steps: (1) biological COD reduction using a membrane bioreactor (MBR) in which the active biomass as well as other particulate matter were completely retained by means of immersed hollow-fibre MF membranes, and (2) subsequent reduction of bacterial germs, residual organics as well as of inorganic constituent compounds by means of downstream two-stage nanofiltration with integrated UV disinfection. This hybrid process was tested by operating a pilot plant (capacity 100 l/h) for 6 months at a fruit juice company in order to treat spent process water (COD: 2,500–6,500 mg/l; electrical conductivity: 2,300–4,700 μS/cm) from the on-site mixing and equalising tank. The process under study proved to be technically feasible and reliable. The treated water was partially desalted and fulfilled both the chemical and bacteriological standards required by the German Drinking Water Act. Therefore, it can be reused, for example, as cooling or boiler make-up water as well as for pasteurisation, preparation of conveyor belt lubricants and bottle washing. Based on the results obtained, a preliminary evaluation was conducted to determine the investment and operating costs required for implementation of the tested hybrid process.