Chemical Oxygen Demand Levels Research Articles

High-speed rail and firms' environmental performance: empirical evidence from China.

Developing countries are struggling to balance the economic development and environment protection. This paper examines the impact of high-speed rail (HSR) on firm-level environmental performance in China. Using the staggered expansion of China's passenger-dedicated HSR and the panel data of Chinese manufacturing firm-level data from 2002 to 2012, we find that firms exhibit a lower level of chemical oxygen demand (COD) emissions after the opening of HSR. The average geographical slope of city is used as an instrumental variable to address the potential endogeneity problem of the HSR variable. Furthermore, the reduction effect of HSR introduction on firms' COD emission intensity is more pronounced for firms that located in eastern regions as well as technology-intensive and labor-intensive firms. Agglomeration economies, scale effects, and technological innovation are three plausible channels that allow HSR to promote firm environmental performance. Our paper provides new insights into the impacts of introduction of HSR on firm environmental performance and the development of green city.

Evaluation of chemical compounds in Plectranthus barbatus leaves extract for application in reduction of tannery wastewater toxicity

Plectranthus barbatus Andr. grows in Kenya, sub-Saharan Africa, Australia, Brazil and Asia and is one of the most important species of the Lamiaceae family. The plant is widely mentioned in traditional medicine in Africa and Asia. Some of the compounds previously isolated from the plant include diterpenoids, phenolic acids and essential oils. The objective of the study was to evaluate and determine the presence of chemical compounds in Plectranthus barbatus Andr. leaves extract of tannin nature that can be beneficial ingredients in processing clean leather and at the same time reduce environmental pollution. The Plant’s leaves were collected from Nyamira County then dried and ground to desired mesh before extraction was done with water and 80 % methanol in water. The methanolic solid extract that was recovered after freeze drying was subjected to column chromatography. The pure fractions were analyzed using Nuclear Magnetic Resonance spectroscopy and compared to those previously analyzed using High Pressure Liquid Chromatography. Some of the compounds isolated include phenolics e.g. Para-Hydroxybenzoic acid and Diterpenes. Water solid extract was used in pre-tanning and re-tanning applications followed by analysis of Biological Oxygen Demand, Chemical Oxygen Demand, pH and total chrome content of respective wastewaters. Tannery liquor from re-tanning and pre-tanning combinations with Plecranthus barbatus leaves extract showed reduced toxicity to the environment with pH of 7.97 and 2.96 respectively as compared to chrome tannage liquor that recorded a relatively more acidic pH of 2.30. Biological Oxygen Demand, Chemical Oxygen Demand and chrome content levels were 230.00 mg/l, 4520.00 mg/l and 9.69 ppm respectively for effluent from Plectranthus barbatus retannage against 320.10 mg/l, 2331.20 and 5.03 ppm respectively from pretannage of the same extract. Permissible limits for pH, Biological Oxygen Demand, Chemical Oxygen Demand and total chrome in discharged tannery wastewater are 5.5 – 10.0, 125 mg/l – 1000 mg/l, 300 mg/l – 3000 mg/l, and 1.0 ppm – 10.0 ppm respectively. Pretanning with Plectranthus barbatus leaves extract during leather processing was more effective is reduction of tannery wastewater toxicity although, the use of pretanning and retanning in a single tannage might yield more promising results.

Water Quality Indices and Potability Assessment of Three Streams in Akwa North and South Local Government Areas, Anambra State, Nigeria

management of water quality, control of water pollution and environmental protection for preservation of living conditions of fresh water bodies for the future necessitated careful routine monitoring. Therefore, the objective of this paper is to assess the water quality indices and anthropological suitability of three streams in Akwa North and South Local Government Areas, Anambra State, Nigeria. Water samples were collected and analyzed for physicochemical properties using standard procedures and the quality assessed using water quality index model. The result results revealed that the water samples from the three sampling sites were acidic to alkalinity in pH, moderate in temperature. The dissolved oxygen (DO), biological oxygen demand (BOD5), chemical oxygen demand (COD), ammoniacal nitrogen and phosphate levels were found to be above World Health Organization (2011) standard limits except total suspended solids values. Water quality index value for all sampling sites ranged from 31.41 to 52.49, respectively revealing the three streams were moderately polluted with different industrial influents. Statistically, there were significant (p < 0.05) differences detected among the means of pathogenic groups, physicochemical parameters and sampling points but non – significant (p > 0.05) differences detected among the means of sampling sites. Thus, the physico- chemical baseline data from this study suggest the public health danger of the three streams to the inhabitants utilizing them as sources of water. Strict preventive measures and awareness campaigns should be put in place by government and water environmental policy makers to guarantee the public health safety of these fresh water resources.

Evaluation of nitrogen removal and nitrous oxide turnovers in granule-based simultaneous nitrification and denitrification system

Nitrous oxide (N2O) is an inevitable intermediate generated during the nitrogen removal process of granule-based simultaneous nitrification and denitrification (SND) system. In order to alleviate N2O production while maintaining a desired total nitrogen (TN) removal level in this system, a comprehensive evaluation of the contribution pathways and process parameters affecting N2O turnovers is keenly required. Therefore, mathematical models were applied to evaluate the impact of operating conditions and unravel potential mechanisms on TN removal performance and N2O production. Simulation results show that higher N2O production (11.6 %–14.2 %) occurs at higher dissolved oxygen (DO) concentrations, lower chemical oxygen demand (COD) levels, longer hydraulic retention time (HRT) and larger granule size in the granular SND system. The relative conversion rates of nitrogenous components in different regions within the granule influence N2O turnovers, with the nitrification process occurring only in the region 200 μm inward from the granule surface and denitrification working throughout the entire granule. In the inner region of the granule (0–300 μm), the heterotrophic bacteria (HB) denitrification pathway dominates N2O production as a source of N2O. While in the outer region (300–450 μm), HB denitrification acts as a sink for N2O and regulates N2O turnovers (i.e. production and reduction of N2O) together with the hydroxylamine (NH2OH) pathway that is the main contributor of N2O production. Moreover, simultaneous adjustment of multiple operating parameters within a certain range can lower the N2O production factor (<0.5 %) while achieving the desired TN removal efficiency (>80 %), resulting in a feasible N2O mitigation strategy.

The feeding habits of small-bodied fishes mediate the strength of top-down effects on plankton and water quality in shallow subtropical lakes

The proliferation of small-bodied fishes in lakes is often accompanied by deterioration of water quality and ecosystem function. However, the potential impacts of different types of small-bodied fish species (e.g., obligate zooplanktivores and omnivores) on subtropical lake ecosystems in particular have been overlooked mainly due to their small size, shorter life spans and lower economic value. Therefore, we conducted a mesocosm experiment to elucidate how plankton communities and water quality respond to different types of small-bodied fishes, including a common zooplanktivorous fish (thin sharpbelly Toxabramis swinhonis) and other small-bodied omnivorous fishes (bitterling Acheilognathus macropterus, crucian carp Carassius auratus and sharpbelly Hemiculter leucisculus). During the experiment, the mean weekly total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), turbidity, chlorophyll-a (Chl.α) and trophic level index (TLI) values were generally higher in treatments where fish were present compared to treatments where fish were absent, but responses varied. At the end of the experiment, phytoplankton abundance and biomass and the relative abundance and biomass of cyanophyta were higher while the abundance and biomass of large-bodied zooplankton were lower in the fish-present treatments. Moreover, the mean weekly TP, CODMn, Chl.α and TLI values were generally higher in treatments with the obligate zooplanktivore, thin sharpbelly, when compared to treatments with omnivorous fishes. Also, the ratio of zooplankton to phytoplankton biomass was the lowest, and the ratio of Chl.α to TP was the highest in treatments with thin sharpbelly. Collectively, these general findings indicate that an overabundance of small-bodied fishes can have adverse effects on water quality and plankton communities and that small-bodied zooplanktivorous fishes likely induce stronger top-down effects on plankton and water quality than omnivorous fishes. Our results emphasise that small-bodied fishes should be monitored and controlled if overabundant when managing or restoring shallow subtropical lakes. From the perspective of environmental protection, the combined stocking of different piscivorous fish species that feed in different habitat types could be a way forward to control small-bodied fishes with different feeding habits, but more research is needed to assess the feasibility of this approach.

Potential of Chlorella sp As A Bioremediation Agent in Tofu Liquid Waste: Literature Review

Tofu liquid waste that contains high levels of COD (Chemical Oxygen Demand), BOD (Biological Oxygen Demand), and TSS (Total Suspended Solid) is usually discharged directly into the waters, causing a foul odor in community drainage and contaminating rivers. This study aims to determine the potential of Chlorella sp as a bioremediation agent in tofu wastewater. This type of research is research that uses the literature review method. The stages of literature collection used in this study refer to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. This stage consists of four procedures, namely, identification, screening, eligibility, and acceptance. This study shows that the microalgae Chlorella sp. can increase population growth and lipid levels, Chlorella sp. Can reduce COD and Nitrate levels contained in tofu liquid waste, and increase the pH from acidic to neutral. Based on the results of the study found, it can be concluded that Chlorella sp has the potential as a bioremediation agent in tofu liquid waste.

Selection of Yarrowia lipolytica Strains as Possible Solution to Valorize Untreated Cheese Whey

Cheese whey management and disposal is a major issue for dairy industries due to its high level of chemical and biochemical oxygen demand. However, it can still represent a source of nutrients (i.e., sugars, proteins and lipids) that can be applied, among other options, as substrate for microbial growth. Yarrowia lipolytica can grow in different environments, consuming both hydrophilic and hydrophobic substrates, and tolerates high salt concentrations. In this work, the lipolytic and proteolytic profile of 20 strains of Y. lipolytica were tested on caseins and butter. Then, their growth potential was evaluated in four types of whey (caciotta, ricotta, squacquerone and their mix). Y. lipolytica showed a very strain-dependent behavior for both hydrolytic profiles and growth capabilities on the different substrates. The best growers for all the types of whey tested were PO1, PO2, and RO2, with the first one reaching up to 8.77 log cfu/mL in caciotta whey after 72 h. The volatile molecule profile of the samples incubated with the best growers were characterized by higher amounts of esters, acids, ketones and alcohols. In this way, cheese whey can become a source of microbial cultures exploitable in the dairy sector.

Efficiency of prefabricated biodigesters in the treatment of domestic wastewater in dispersed rural localities

In most developing nations, poor wastewater management continues to be a significant health and environmental concern. In this context, the research seeks to evaluate the efficiency of the biodigester treatment of domestic wastewater through monitoring and evaluation, based on physicochemical and bacterial parameters to reduce environmental pollution caused by excreta in the Chibaya Baja sector, Peru. Water sampling was done in the influent and effluent of the biodigester, taking samples periodically every 15 days, for 01 months, obtaining 03 samples for physicochemical and bacteriological analysis. According to the results obtained from the laboratory, the efficiency of the domestic wastewater treatment was 59.51% of the biochemical oxygen demand (BOD), 49.16% of the chemical oxygen demand (COD), in oils and fats 35.92%, in total suspended solids 52.78% and fecal coliforms (thermotolerant) 89.19%. A comparison of the parameters evaluated with the maximum permissible limits set by the Peruvian Ministry of the Environment reveals that the levels of BOD and COD exceed the limits. Therefore, this wastewater should not be discharged into water bodies.

Application of Citeromyces siamensis for Molasses Wastewater Decolourization

Abstract Molasses, a brownish black viscous liquid, is a byproduct of the cane sugar process. It finds applications in various industries such as fertilizer production, animal husbandry, alcohol production, monosodium glutamate production, and the production of acetic acid. In Thailand, it is primarily used for alcohol production and as animal feed. However, molasses wastewater is characterized by high levels of biochemical and chemical oxygen demand, as well as suspended solids. Untreated release of this wastewater into the environment can lead to numerous environmental issues. Additionally, the presence of melanoidins in molasses wastewater makes its removal challenging, resulting in a dark colour of the treated water. Discharge of this dark-coloured water into natural water sources can lead to an abnormal discolouration of the water. This study aims to investigate the optimal conditions for utilizing Citeromyces siamensis microorganisms in the biological treatment of molasses wastewater. The experiment was conducted to determine the conditions that facilitate the reduction of colour in molasses wastewater. The findings indicate that the addition of 1 % glucose and 1 % peptone was more effective in decolourizing molasses wastewater using Citeromyces siamensis compared to other nutrient additions. While the addition of additives may incur additional costs, it remains a more economical option compared to the use of chemicals for wastewater colour removal. Furthermore, the use of the additives is considered safe for living organisms.

Ammonia-Nitrogen Reduction in Low Strength Domestic Wastewater by Polyvinyl Alcohol (PVA) Gel Beads

This study aimed to evaluate the efficacy of polyvinyl alcohol (PVA) gel beads as an immobilized biofilm carrier to enhance the reduction rate of Ammonia-Nitrogen (NH3-N) and Chemical Oxygen Demand (COD) in domestic wastewater. Laboratory scale reactors were developed to assess the reduction levels of ammonia-nitrogen and COD with and without PVA gel beads using optimal and non-optimal treatment mode settings based on operation procedures from the sewage treatment plant in Taman Kajang Utama, Selangor. The treatment method used is an activated sludge sequencing batch reactor with a treatment cycle duration of 288 minutes. The findings showed the ammonia-nitrogen reduction by non-optimal treatment mode is more effective, with a reduced rate of 62.96% to 65.71% compared to optimal treatment mode with a reduced rate of 30.94% and treatment without PVA gel beads (optimal and non-optimal) with a reduced rate of 32.41% to 47.85%. The ammonia-nitrogen reduction rate using PVA gel beads for non-optimal treatment mode was significantly increased from 17.86% to 18.82% and complied with ammonia-nitrogen reduction parameter 10mg/L, Standard A of Environmental Quality (Sewage) Regulations 2009 (EQSR 2009). The rate of COD reduction using the non-optimal treatment mode was also more stable, with a reduced rate of 70.68%. It was also found that the COD reduction rate using PVA gel beads for the non-optimal mode was better than the optimal mode, which was 70.68% compared to 42.0%, and both treatment modes complied with COD reduction parameters 120mg/L, Standard A of EQSR 2009.

Ex-situ biological treatment of industrial saline seafood wastewater by salt-tolerant mixed cultures and phytotoxicity evaluation

In the framework of circular economy, this study assessed the ex-situ biodegradation and desalination of saline non-sterilized seafood wastewater (SFW) by new salt-tolerant mixed bacterial cultures, followed by its phytotoxicity evaluation. These cultures were characterized through 16S amplicon sequencing, an advanced tool to process the biodiversity of samples empowering applicability to advanced bioprocessing of SFW. The mixed cultures had high relative abundance of Pseudomonas and Aeromonas, and abundance of Acinetobacter, Myroides and Chryseobacterium. The biodegradation potential, growth kinetics and specific growth rate of the mixed cultures were determined using varying concentrations of SFW (20% and 80% v/v). The process was completed in just 24 h resulting in no odour and colour. The mixed cultures were also combined. Effective Chemical Oxygen Demand (COD) removal (36.2–89.1%) was achieved by the mixed cultures and their combinations. The mixed cultures resulted in significant salt content reduction (77.5–83.3%). The considerably lower levels of COD (<900 mg/L) and salt content achieved, in most cases, is a step towards in-situ SFW treatment before entrance to the sewage system. Among all, mixed Pseudomonas sp. dominant cultures were the most promising for further in-situ bioprocessing studies. In addition, the biotreated SFW supernatant, which was not overly-diluted using freshwater, could potentially be reused in agriculture, as the germination index was higher than 50% upon seed and root growth of tomato and lettuce. It contained approximately 0.03% total nitrogen and 0.01% phosphate which may irrigate to plants providing additional nutrients.

Persulfate degradation of wastewater from hydrothermal carbonization of food waste catalyzed by activated carbon

Hydrothermal carbonization (HTC) is highly acknowledged for its ability to convert wet food waste into high calorific value hydrochar at a fast rate. However, the liquid by-product from the process, named HTC wastewater, contains high level of chemical oxygen demand (COD) of 40,000–55,000 mg/L. This HTC wastewater can greatly pollute the environment if it was released without a proper treatment, and hinder the industrial application of HTC technology. In this study, hydrochar was produced via HTC process at 250 °C, and KOH activation was employed to further improve the physical structure of the hydrochar to prepare activated carbon (AC). The obtained AC had the mesoporous structure with specific surface area of 1807.42 m2/g. The AC was used to catalyze persulfate (PS) oxidation for the degradation of HTC wastewater. The experiment of catalytic persulfate degradation of HTC wastewater was designed by the central composite design (CCD) method, and optimized by using response surface method (RSM). The experimental results were statistically discussed by the analysis of variance (ANOVA). The optimal condition determined by CCD model was PS dosage = 6.20 mmol, temperature = 32.47 °C, and pH value = 3.69, achieving a COD removal efficiency of 78.94%. The hydrochar catalyzed persulfate degradation of HTC wastewater caused a great reduction of its pollution degree, which can be a promising pretreatment for HTC wastewater with minimal effort and cost.

Domestic Wastewater Treatment with Multi Soil Layering Method with Variations of Hydraulic Loading Rate (HLT) And Organic Materials at Anaerobic Conditions

Domestic wastewater is the largest producer of wastewater in Indonesia which comes from the remnants of household activities. Hazardous substances such as Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), Oil and Fat contained in wastewater can cause health problems for humans. In this study, domestic waste treatment was carried out using the Multi Soil Layering (MSL) method. The MSL system is a wastewater treatment method that utilizes the ability of soil as the main medium and several other media such as zeolite, gravel, charcoal, and sawdust which are formed in a multilevel brick pattern. The independent variables are the variation of soil mixture with sawdust (M1) and soil mixture with charcoal (M2) and also variations of Hydraulic Loading Rate namely HLR 500 L/m2.day (H1), 750 L/m2.day (H2), 1000 L/m2.day (H3). The characteristics of domestic wastewater include pH 6, BOD 236 mg/L, COD 514 mg/L, TSS 114 mg/L, Oil and Fat 8200 mg/L. The results showed that the best variation in the removal of pollutant levels was a mixture of soil with charcoal (M2) and HLR 500 L/m2.day (H1), with the average efficiency in reducing BOD, COD, TSS, Oil & Fat levels, respectively. 86.39%, 78.29%, 86.56% and 79.60%.

Analysis on Impact of Kukrail Nala in Gomti River Pollution and Its Effect on Adjoining Ground

Abstract: This study set out to ascertain the degree of contamination in the Kukrail Nala and how much it contributed to the pollution of the Gomti River. The Kukrail Nala begins in the Kukrail Forest and confluences with the Gomti River after travelling approximately 26 kilometres, passing through the centre of the city. As a result, the Kukrail Nala's pollution will have an impact on the health of Citizens, particularly those who live nearby. The Gomti River and Kukral Nala run through Lucknow, the state capital of Uttar Pradesh. Due to human involvement and the discharge of municipal and industrial trash, Kukrail Nala and Gomti River, located in the centre of the Ganga Plain, suffered severe damage downstream of Lucknow. The nala is extremely contaminated, with high levels of Biochemical oxygen Demand (BOD) and Chemical oxygen demand(COD), even in the summer. Due to the extremely low and almost negligible flow of the Kukrail Nala, it is likely that the pollution may percolate there and eventually reach the ground water. People who live close to the nala regularly depends upon the groundwater for various activities like drinking, bathing and other household activities ground water, which could have an impact on their health. Speaking of more than just humans, it also harms animals within and outside of water bodies. The way that technological advancements are affecting everyone's lives is having a tremendously negative impact on natural resources. This study focuses on the extent to which Kukrail Nala has been dangerously exploited and how it may have an impact on other larger water sources and as well effect being associated with these water bodies.

Sequential coagulation/flocculation and sonolytic oxidation using persulfate and hydrogen peroxide for real rubber processing industry wastewater treatment: Kinetic modelling and treatment cost analysis

Rubber processing industry consumes huge quantity of water, uses chemicals and produces enormous quantity of toxic wastewater with high level of chemical oxygen demand (COD), solids and turbidity. In this study, treatability of rubber processing industry effluent using a sequential coagulation-flocculation (CF) followed by sonolytic oxidation was studied with the real wastewater collected from a rubber processing industry located near to Agartala, Tripura, the second largest rubber producing state in India. Initially aluminium sulfate was used as coagulant in the CF process to reduce the COD of the wastewater followed by only ultrasonication (CF + US), sonolytic oxidation using persulfate (CF + US + PS), sonolytic oxidation using hydrogen peroxide (CF + US + H2O2) and sonolytic oxidation using both persulfate and hydrogen peroxide (CF + US + PS + H2O2) as oxidants. Real rubber processing wastewater was also treated with only sonication (US). Firstly, the only CF process (aluminium sulphate dose: 500 mg/L) could reduce the COD of wastewater from 18267 mg/L to 12800 mg/L (COD removal: 29.93 %). Thereafter, CF + US (sonication time: 30 min), CF + US + PS (PS dose: 500 mg/L), CF + US + H2O2 (H2O2 dose: 0.75 mmol/L), and CF + US + PS + H2O2 (PS dose: 500 mg/L and H2O2 dose: 0.75 mmol/L) resulted to effluent COD value to ∼ 6800 mg/L, 4200 mg/L, 3200 mg/L and ∼ 1600 mg/L, respectively. The CF + US + PS + H2O2 process was the best option among the considered combination of treatment techniques to treat the real rubber processing industry effluent in terms of COD removal (%). Kinetic analysis for the degradation of COD in various treatment processes were found to be consistent with pseudo second order kinetic model. The treatment cost analysis revealed that COD degradation by CF + US + H2O2 process cost ∼ 2.5 USD/kg of COD removal with 82.48 % of COD removal.

Biodegradation and power production kinetics in microbial fuel cell during rice mill wastewater treatment

The influence of the initial substrate concentration of rice mill wastewater on substrate degradation rate and power production in a dual-chambered MFC was explored over a wide range of chemical oxygen demand (COD: 500–6000 mg/L) and lignin (77.5–930 mg/L) levels. Within a limited concentration range, increasing COD concentration increased degradation rates and electricity generation, but both processes were hindered at high substrate concentrations. A maximum power density of 4.3 W/m3 was attained in a MFC operated with an initial COD concentration of 2480 ± 17 mg/L which can be attributed to the low ohmic resistance (23.8 Ω) due to better solution conductivity. Different kinetic models were used to examine inhibition kinetics from an electrical perspective. The relationship between power density and COD concentration was best described by Han–Levenspiel model. The maximum power density, half-saturation constant, and critical inhibitory concentration were predicted to be 4.56 W/m3, 799.6 mg/L, and 7627 mg/L, respectively. A maximum lignin degradation rate of 0.063 ± 0.007 kg/m3∙d was achieved at a lignin concentration of 387.5 ± 2.8 mg/L which accounts for 83.17 ± 0.26 % removal efficiency, suggesting the possibility of lignin degradation in MFC even at higher concentrations. The detection of low molecular weight degradation by-products of lignin in the effluent sample further confirmed the ability of exoelectrogens to degrade lignin.

COD Reduction of Aeration Effluent by Utilizing Optimum Quantities of UV/H2O2/O3 in a Small-Scale Reactor

Extensive research has been carried out to figure out safe means of disposing various industrial effluents. Industrial wastewaters from the aeration industry such as heavy metals and oily substances contain a high degree of contamination. The advanced oxidation process is one of the most effective and rapid methods of removing contaminations, which can lead to a high chemical oxygen demand (COD). The aim of the present study is to reduce the COD of an aeration effluent with the initial COD of 13,004 mg/L. About 20 sets of experimental tests were conducted to identify the contribution of H2O2, O3, and UV to the treatment process. The influence of the quantities of additives and the dose of the UV irradiance were, too, among the subjects of the study. These factors were altered throughout the experiments and their mutual effects were measured. To design the experiments, Minitab software 16 was utilized. The experimental conditions were set at the standard values of 25 °C and 1 bar to minimize any uncertainty. Based on the results, a correlation was derived, which was capable of expressing the effects of the input parameters (AOPs parameters) on the response (the COD level). Finally, the optimization process was conducted to find the quantities of H2O2, O3, and UV irradiance required to decrease the CODs of the effluent to their lowest possible. Based on the findings, when the doses of H2O2, O3, and UV to the treatment process were 40 mg/L, 8 mg/L and 86 mWs/cm2, respectively, the COD percent change was 51.5%.

The challenges and treatment of abattoir effluents: a South African perspective

Abstract South Africa's (SA's) water resources have been severely affected by the demand for meat products. The growing population has resulted in an increase in food production, increasing the number of abattoirs from 25 in 1988 to 420 in 2021. Organic matter is abundant in abattoir effluent, with chemical oxygen demand levels reaching 9,000 mg/L. To reach permissible discharge limits, various methods such as sequential bed reactor, granular sludge bed, membrane bioreactor, and membrane filtration have been adopted. However, some abattoirs do not meet municipal regulatory requirements. As a result, practical and cost-effective approaches such as biofilm reactors were developed to encourage abattoirs to employ water treatment technology. Bioreactor-based technologies have proven to be successful, with more than 90% efficiency. Fat, oil, and grease (FOG) are problematic in abattoir effluents as they emit odours, attract insects, and impair the biodegradability of wastewater. For this reason, hydrolysis using a novel agent (Eco-flush™) has shown to be an effective technique for decreasing FOG. During treatment, biogas produced by anaerobic degradation may be utilized as an energy source to alleviate SA's energy problem. This review aims to outline the challenges related to abattoir wastewater in SA and highlight the gaps associated with abattoir wastewater treatment.

A Closed Loop Wastewater Biorefinery Based on the Recently Introduced SHEFROL Reactor and Two Freely Available Macrophytes

AbstractWith an objective to develop a closed loop wastewater biorefinery, the performance of two free floating aquatic weeds water hyacinth (Eichhornia crassipes, Mart, Solms) and salvinia (Salvinia molesta, Mitchell) is explored when either is used as the main bioagent for treating sewage in “sheet flow root level” (SHEFROL) bioreactors. Both the macrophytes prove to be easy to propagate and maintain while they are able to help in achieving significant primary, secondary, and tertiary treatment steps of greywater in a single step. Water hyacinth is able to remove suspended solids, chemical oxygen demand (COD), biological oxygen demand (BOD), total Kjeldahl nitrogen, soluble phosphorous, zinc, copper, nickel, and manganese to the average extents of 81%, 79%, 43%, 41%, 40%, 36%, 34%, and 29%, respectively. The reduction in COD and BOD levels achieved by salvinia is marginally lesser than by water hyacinth but in terms of the removal of other pollutants, the performance of salvinia is comparable to that of water hyacinth. It is possible to convert the dead or harvested plants to organic fertilizer thus making it a closed‐loop system with no waste of its own.

Membrane fouling behavior in membrane bioreactors for nitrogen-deficient wastewater pretreated by ammonium ion exchange

Nitrogen is a critical element closely related to the synthesis of cellular membrane fouling behaviors in membrane bioreactors (MBRs). In this study, a novel pretreatment process by coupling chemically enhanced primary treatment (CEPT) with ammonia nitrogen ion exchange and regeneration (AIR) was proposed to analyze their influences on sludge properties and membrane fouling in MBRs. The MBRs with CEPT and AIR pretreatment obtained the effluent with chemical oxygen demand (COD) and ammonium nitrogen (NH4+-N) levels comparable to the conventional anoxic/aerobic MBR, but with much lower concentrations of total nitrogen (≤3.0 mg/L) and total phosphorous (≤0.15 mg/L). CEPT and AIR remarkably removed particles and soluble proteins from the influent, prohibited EPS secretion by 62.9–79.1% and elevated viscoelasticity of EPS, and thus alleviated membrane fouling. Membrane foulant in the experimental MBRs had unstable EPS structures easily detached, and low biofilm roughness to prevent the adsorption of organic matters. Nitrogen load had significantly positive correlations with EPS contents, viscoelasticity of EPS, and the total filtration resistance. The nitrogen-deficient condition enriched quorum quenching bacteria and microbes surviving retarding EPS production, and inhibited the overgrowth of filamentous bacteria. Therefore, nitrogen separation from wastewater in advance can effectively alleviate membrane fouling and improve pollutant removal in MBRs.