Biochemical Oxygen Demand Removal Research Articles

Characterization of Low-Volume Meat Processing Wastewater and Impact of Facility Factors

Low-volume meat processing facilities often rely on decentralized wastewater treatment due to cost constraints and the lack of access to centralized treatment. Improved characterization of these facilities’ wastewater is crucial for meeting local groundwater discharge permits. This study also directly correlates treatment systems and facility characteristics to the results of the characterization. The total nitrogen (TN), biochemical oxygen demand (BOD), and phosphorus (P) reductions ranged from −15% to 83%, 43% to 95%, and −75% to 62%, respectively. Slaughtering and smoking were found to significantly increase nutrient concentrations. The average TN leaving the slaughterhouses and processing-only facilities was 519 mg/L-N and 154 mg/L-N, respectively. The average BOD produced by the slaughterhouses and processors was 3002 mg/L and 1660 mg/L, respectively. Filtration was found to reduce BOD, chemical oxygen demand (COD), and trace metals. Aeration in a treatment lagoon was found to significantly reduce BOD, COD, and N compounds. The results indicate that even simple decentralized wastewater treatment systems, combined with facility management practices, can substantially reduce permitted wastewater characteristics. The facility with the best BOD removal had an effluent value of 71.3 mg/L, representing a 96% reduction. The facility with the best TN removal had an effluent value of 20 mg/L, representing a 92% reduction prior to discharge.

The comparison between different types of constructed wetlands for biochemical oxygen demand removal efficiency

This research shows efficiency of constructed wetlands (CWs) to purify waste water in the case of Biochemical Oxygen Demand (BOD). CWs such as surface flow (SF), subsurface flow (SSF), and hybrid (HYB) systems have been compared to provide an analysis about which system has better performance for BOD removal efficiency. Data were collected from different scientific articles and from all over the world. Meta-analysis technique was employed to aggregate data from scientific sources, facilitating hypothesis testing, and comparisons between different types of CWs. All the systems of CWs show satisfactory removal efficiency. HYB systems are shown to be the most efficient. One-way analysis of variance (ANOVA) has been applied to analyze differences between respective CWs using R software. It shows that there is a statistically significant difference between different types of CWs. Post-hoc Tukey?s Honestly Significant Different (HSD) analysis demonstrates a statistically significant difference between SF and HYB systems in the case of BOD removal efficiency. Also, Post-hoc Tukey?s HSD shows statistically significant difference between SSF and SF CWs. On the other hand, Post-hoc Tukey?s HSD does not show statistically significant difference between HYB and SSF CWs. The significant reduction rates for BOD removal efficiency, demonstrates that CWs can be used to diminish this kind of pollution.

Adsorptive removal of biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) from greywater using activated carbon prepared from tropical almond and palm kernel shells

This study assesses the reduction of 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) of household greywater using palm kernel activated carbon (PKAC) and tropical almond activated carbon (TAAC) produced from locally available materials in a kiln at 800oC and activated using steam at a flowrate of 120 mL hr-1. Brunauer-Emmet-Teller (BET) surface area determination revealed that PKAC had a larger surface area than TAAC. Scanning electron microscope (SEM) imagery of the carbons also revealed amorphous and large internal shapes for TAAC while crystalline and closed packed shapes for PKAC. X-ray diffraction (XRD) analysis indicated that the major component present in the PKAC and TAAC was carbon and other allotropes of carbon. Batch results showed that reduction of BOD5 and COD was affected by particle size. The maximum percentage reduction of BOD5 and COD by PKAC was 76% and 65% respectively while reduction by TAAC was 62% and 52% respectively. The adsorption process was well described by the Freundlich adsorption isotherm. The studies showed that PKAC is a better adsorbent for reducing BOD5 and COD from domestic greywater as compared with TAAC. The PKAC is a potential low-cost adsorbent for BOD5 and COD removal from domestic greywater.

Evaluation of Accumulation Potency of Arka Plant Varieties for Metals and Nutrients through Natural Biological Treatment

This study aims to evaluate the effectiveness of a natural biological treatment system for wastewater using Red soil, Arka Darshan, Arka Tilak, Arka Nirantara, and Arka Prajwal plants. The system employs clay as a natural nanomaterial for adsorption of substances such as nitrates, phosphates, potassium, and heavy metals. The soil contains numerous microorganisms that decompose organic matter into simpler compounds, while the plants use phytoremediation to uptake heavy metals and nutrients. The study measured the system’s efficiency in reducing Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Phosphate, Magnesium, Zinc, Nitrate, Sodium, and Potassium. The results showed that the system had an average efficiency of 98% in COD and 96% in BOD removal, and contributed an efficiency of 99% TSS and 46% TDS. The system also removed nitrates and phosphates, which cause eutrophication in water bodies, by 76% and 72%, respectively. Additionally, heavy metals like chromium, Nickel and Zinc were reduced by up to 81%, 71% and 59%. The study suggests that the natural biological treatment system is a sustainable and effective alternative to conventional wastewater treatment, particularly in sparsely populated rural areas. Therefore, we can conclude that this system has potential for wider adoption in treating wastewater.

Assessment of Rice Husk-Based Activated Carbon as Adsorbent in Domestic Wastewater Treatment

Indiscriminate discharge of wastewater into the environment is of utmost concern, especially in developing countries. This study evaluated the efficiency of rice husk based activated carbon in wastewater samples harvested from a students’ hostel and a restaurant within the Federal University of Technology, Akure. The adsorbent used was produced from rice husk using hydrogen tetraoxosulphate (VI) acid (H2SO4) as the activating agent. The aim of this study was to assess rice husk-activated carbon for the reduction of physicochemical parameters such as hardness, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), total dissolved solid (TDS), total suspended solid (TSS), and heavy metals which include chromium (Cr), lead (Pb), manganese (Mn), and iron (Fe). The wastewater samples were treated using activated rice hush ash of particle size (180 µm) at four different doses (30, 35, 40, 45 grams/400 ml). The results showed that the different doses of activated carbon had different removal efficiency. It was observed that the optimum dosage was 40g for DO, COD, BOD, and TDS while 30g was optimum for Hardness. It was also observed that an increase in the concentration of rice husk adsorbent led to an increase in the removal efficiency for the heavy metals (Cr, Mn, Pb, and Fe). The maximum percentage removal of DO, COD, BOD, TDS, and TSS, with rice husk was 21%, 58%, 72%, 21%, and 57% respectively. After the treatment of the domestic wastewater and comparing with the WHO standard, the treated wastewater quality was found to be safe for direct discharge into surface water bodies and irrigation purposes.

Efficient treatment of tannery wastewater through aeration, coagulation, and algal pond.

Tannery wastewater effluents contain many toxic and carcinogenic heavy metals and physiochemical parameters that need to be removed before these effluents enter in the main water bodies or rivers. In this study, the effluents from the tannery industry are treated through aeration, coagulation, and Chlorella vulgaris pond treatment processes for the removal of physiochemical: parameters only. The effect of removal efficiencies (%) was studied on the physicochemical parameters, including salinity, electrical conductivity (EC), total dissolved solids (TDS), turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD). The key results showed that the removal of EC, TDS, turbidity, TSS, BOD, and COD was 80.2%, 67%, 81%, 80.8%, 68.6%, and 100%, respectively, in raw wastewater treatment having 25, 50, and 70 g of algae C. vulgaris doses. The removal efficiencies (%) of salinity, EC, TDS, turbidity, TSS, BOD, and COD were 83%, 87.1%, 77.1%, 80%, 40%, 97%, and 98%, respectively, during coagulated wastewater treatment with three doses of algae. The observed improvement in treated wastewater indicated that the removal efficiencies (%) of salinity, EC, TDS, turbidity, TSS, BOD, and COD were 85.7%, 39.3%, 81.3%, 67.8%, 50.3%, 97%, and 98%, with C. vulgaris. This study confirmed that the treatment of tannery wastewater by these processes increased the pollutant removal efficiencies as all the physiochemical parameters were exceeding the permissible limits. This research will be helpful to treat the industrial wastewaters or effluents before it further mixes up in the main water streams. In this way, water quality will be better, aquatic life will be saved, and further researchers can analyze more ways for efficient treatments as they have a baseline data through this study findings. One of the most pollutant sources in terms of both physical and chemical parameters is the produced wastewater from tannery industries. The effluents from tannery industry are treated through aeration, coagulation, and algae ponds treatment processes. These treatment made the tannery wastewater as environmental friendly.

Evaluation of combined efficiency of conventional coagulation-flocculation process with advanced oxidation process (sulfate-hydroxyl radical) in leachate treatment

This study evaluated a novel municipal solid waste leachate (MSWL) treatment system called the Batch flow leachate treatment system (BFLTS). This process uses a combination of coagulation/flocculation (C-F), advanced oxidation (sulfate-hydroxyl radical), and extended aeration of activated sludge (EAAS) to treat MSWL. The results indicated that the primary treatment phase using coagulation/flocculation with 0.8 g L<sup>-1</sup> FeCl<sub>3</sub> at pH 6 achieved 67% turbidity and 63% chemical oxygen demand (COD) reduction. The secondary treatment phase with the presence of both K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> and H<sub>2</sub>O<sub>2</sub> peroxides was more efficient than single peroxide processes. While PS-based or H<sub>2</sub>O<sub>2</sub>-based single peroxide processes are less effective (UV-PS 65.7%, UV-H<sub>2</sub>O<sub>2</sub> 43.2%, Heat-PS 58.6%, Heat-H<sub>2</sub>O<sub>2</sub> 34.5%, and Heat-PS/H<sub>2</sub>O<sub>2</sub> 74.8%). The UV-PS/H<sub>2</sub>O<sub>2</sub> system achieved the highest COD removal rate of 89.4%. In the third treatment phase, the efficient removal of COD and Biochemical oxygen demand (BOD) under optimal operating conditions was 87.3% and 94.7% respectively. Overall, the BFLTS treatment system has demonstrated high efficiency in removing COD, BOD, TSS, Turbidity, TKN, and Heavy metals by 99%, 98%, 97%, 89%, 86%, and 98%, respectively. This hybrid process has potential for reducing organic load in MSWL and can be used for various leachates.

Challenges to Accurate Estimation of Methane Emission from Septic Tanks with Long Emptying Intervals.

Septic tanks in low- and middle-income countries are often not emptied for a long time, potentially resulting in poor pollutant removal efficiency and increased greenhouse gas emissions, including methane (CH4). We examined the impact of long emptying intervals (4.0-23 years) on the biochemical oxygen demand (BOD) removal efficiency of 15 blackwater septic tanks and the CH4 emission rates of 23 blackwater septic tanks in Hanoi. The average BOD removal efficiency was 37% (-2-65%), and the average CH4 emission rate was 10.9 (2.2-26.8) g/(cap·d). The emptying intervals were strongly negatively correlated with BOD removal efficiency (R = -0.676, p = 0.006) and positively correlated with CH4 emission rates (R = 0.614, p = 0.001). CH4 emission rates were positively correlated with sludge depth (R = 0.596, p = 0.002), but against expectation, negatively correlated with BOD removal efficiency (R = -0.219, p = 0.451). These results suggest that shortening the emptying interval improves the BOD removal efficiency and reduces the CH4 emission rate. Moreover, the CH4 emission estimation of the Intergovernmental Panel on Climate Change, which is a positive conversion of BOD removal, might be inaccurate for septic tanks with long emptying intervals. Our findings suggest that emptying intervals, sludge depth, and per-capita emission factors reflecting long emptying intervals are potential parameters for accurately estimating CH4 emissions from septic tanks.

Pretreatment of Landfill Leachate Using Hydrodynamic Cavitation at Basic pH Condition

The leachate generated from a landfill can cause significant harm to the environment and human health, so it must be treated before being discharged. A biochemical method is effective to treat the landfill leachate, but it requires a physicochemical pretreatment to help reduce the organic load and improve the biodegradability of the landfill leachate. In this work, hydrodynamic cavitation was used to pretreat the landfill leachate due to it being cost-effective, without additional chemicals, and environmentally friendly. The pretreatment experiments were conducted under an inlet pressure of 0.4 MPa and a basic pH. The influence of operating parameters such as the orifice opening rate, the arrangement of orifices, and the reaction time on the chemical oxygen demand, ammonium nitrogen, and biochemical oxygen demand removal in landfill leachate was studied, and the energy efficiency was evaluated. The results showed that under the above conditions, the removal rate for the chemical oxygen demand of the orifice plate with an annular orifice arrangement was better than that of the orifice plate with a radiation orifice arrangement, and the orifice plate with an orifice opening rate of 0.0417 had the best effectiveness. The energy efficiency under these two optimization conditions was also the highest. When the optimal operation time was 60 min, the removal rate of the chemical oxygen demand was 22.63%. The biodegradability of the landfill leachate was significantly improved with BOD5/COD increasing by 57.27%. The study provides a theoretical basis and data support for the application of hydrodynamic cavitation as a low-cost and efficient treatment method in the pretreatment of landfill leachate.

Prevention of water pollution through combined sewer overflow using high-speed biofiltration in urban watershed

Over recent decades, the rural areas of Korea, including containing source waters, have become extensively developed. Combined sewer systems (CSSs) have been constructed to collect the sewage generated from these areas. Presently, it is common to experience localized heavy rain events, likely due to climate change, and sometimes, the volume of rainfall can become too high for a CSS to handle. In these cases, combined sewer overflow (CSOs) occurs, contaminating surface water, which may have been used as source water. Therefore, the Korean government will begin regulating the biochemical oxygen demand (BOD) of CSOs occurring during first flushes of less than 40 mg/L from 2024 onwards. In this study, a biofiltration-based technology was proposed to treat CSOs. Thus, this study aimed to remove BOD from CSO using this biofiltration system to contain cube-type media. For this, two different loading rates were tested on a pilot scale. Although the proposed system resulted in a footprint of only 10 % of that of a conventional activated sludge system, it was still capable of achieving efficient BOD removal. At a high loading rate, BOD removal efficiency was observed at approximately 53 %, and when this loading rate was reduced by 50 %, the removal efficiency was slightly improved to about 58 %. In both cases, the BODs of treated CSOs could be maintained below the proposed future standard: 31 mg/L and 28 mg/L for high and low loading rates, respectively. Therefore, the proposed system could potentially be preventing environmental contamination from COSs.

Magnetically recoverable copper ferrite for catalytic ozonation of surfactant-containing simulated laundry wastewater

Laundry detergent wastewater is a valuable renewable resource released in vast quantities that can be reused to alleviate water shortage issues. The primary contaminant found in laundry wastewater, which is the surfactant has harmful impacts on the ecosystem, resulting in the eutrophication of lakes and rivers. This study examines the effectiveness of catalytic ozonation treatment using a magnetically recoverable copper ferrite to treat surfactant-containing laundry wastewater. A magnetically recoverable copper ferrite was successfully prepared using a modified sol-gel method for the remediation of detergent wastewater. The modified sol-gel method uses a low calcination temperature (350 °C) synthesis process to prepare spinel-structured copper ferrite. The physicochemical properties of the prepared copper ferrite were evaluated using XRD, FT-IR, XPS, FESEM, BET, and VSM analyses. Various process parameters such as initial concentration, solution pH, catalyst dosage, and ozone dosage were investigated to reveal the ozone activation capability and catalytic mechanism. The surfactant degradation performance in catalytic ozonation was compared with the non-catalytic ozonation, respectively. Results indicated that the copper ferrite exhibited excellent ozone activation ability, with 98.4% of surfactant degradation at an initial concentration of 10 ppm, a reaction time of 30 min, a catalyst dosage of 0.2 g/L, an initial pH of 7 and an ozone dosage of 3.68 mg/min. The chemical oxygen demand (COD) elimination rate at this setting was 79.5% compared to 26.7% for non-catalytic ozonation. The biochemical oxygen demand (BOD) removal percentages for ozonation and catalytic ozonation were 33.3% and 93.3%, respectively. Simple economical assessment using electrical energy per order (EE/O) showed that low electrical energy was consumed by the catalytic ozonation (60.31 kWhm−3order−1) compared to the ozonation process (381.68 kWhm−3order−1). The copper ferrite can be quickly recovered from the treated water by applying an external magnet, enabling catalyst reuse and easy collection of treated water. Several limitations restrict its application, including metal leaching and catalyst agglomeration. This is the first application of copper ferrite-catalysed ozonation for the remediation of laundry effluent-containing surfactants. These findings showed a vast application potential of catalytic ozonation using copper ferrite for surfactant-containing laundry wastewater treatment.

Applicability of hybrid treatment to reduce the footprint of domestic and industrial wastewater of developing countries

Wastewater pollution is a serious concern, especially in developing countries such as Pakistan. The untreated domestic and industrial wastewater is typically discharged into sewers, natural drains, or water bodies. There is a dire need to evaluate the applicability of low-cost treatment technologies. Hybrid wastewater treatment (HWWT), comprising of chemically enhanced primary treatment (CEPT) and intermittent sand filter (ISF), was adopted to treat domestic, process and manufacturing, and food industry wastewaters. The wastewater pollution and contamination were assessed in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). The removal efficiency (RE) performance of HWWT was compared with the CEPT system only. Considering the CEPT only, the RE of BOD was ≈70 % for domestic, >80 % for process and manufacturing, and ≈50 % for the food industry. For COD, the RE was high in process & manufacturing (RE ≈ 81 %), followed by food (RE ≈ 55 %) and domestic wastewater (RE ≈ 17 %). Furthermore, the CEPT provided >95 % TSS removal in all wastewater types. The HWWT increased TSS removal by ≈2 %, BOD removal by ≈13 %, and COD removal by ≈27 % compared to the CEPT system. Therefore, HWWT proved more efficient in treating both domestic and industrial wastewater. The HWWT reduced the greywater footprint (GWF) by 50–60 % when compared to the CEPT system. This study provided knowledge of the characteristics of domestic and industrial wastewater. Furthermore, provides a basis to assess the applicability and performance of various wastewater treatment systems under given settings.

Exploring the Efficacy of Bacillus oceanisediminis Ba9 from Asian Seabass Cage Sediment in Saline Wastewater Treatment

Preventing toxicity in aquaculture systems from ammonia and nitrite is important. This study isolated the salt-tolerant Bacillus sp. strain Ba9 from bottom sediment under an Asian Seabass (Lates calcarifer) cage cultivating at Koh Yor, Songkhla, Thailand. Morphological characteristics showed that strain Ba9 was rod-shaped, endospore-forming, and Gram-positive. Strain Ba9 grew well at a salinity of 1.5 to 4.0% NaCl. The catalase test of the isolate was positive, while the oxidase test was negative. Based on 16S rRNA gene sequencing data and phylogenetic tree analysis, strain Ba9 was identified as B. oceanisediminis with 97% similarity (strain HQB337T). The result showed that the ammonium removal efficiency of Ba9 in a high ammonium medium was 64.24%. The nitrite and nitrate production were 0.10% and 0.08%, respectively. Consequently, sucrose had been the optimal carbon source for Ba9, which showed ammonium removal was 61.05%. Ammonium sulfate is the most suitable for ammonium oxidation, with 50.53% for the nitrogen source. The optimal C/N ratio of strain Ba9 was 8, with 71.15% ammonia removal. For wastewater improvement, strain Ba9 was inoculated into artificial wastewater for 14 days. The result showed that the ammonium removal efficiency of Ba9 was 96.87%. In addition, the biochemical oxygen demand (BOD) removal efficiency of Ba9 was 90.86%. From this result, the salt-tolerant B. oceanisediminis Ba9 has a high potential as a microbial product for water quality management in marine aquaculture.

Assessment of solar photocatalytic degradation of textile wastewater by ZnO-based reactors

Abstract The present study deals with treating the textile wastewater of Jodhpur city in Rajasthan, India employing a photocatalysis technique. Jodhpur has a number of textile industries and efficient treatment of its effluents has been a major problem in the region. An effort has been made to resolve this issue through this study. A wastewater treatment unit was setup which involved coagulation and flocculation, sand filter, photoreactor, and activated carbon filter processes. ZnO-based semiconductor, coated on galvanized iron (GI) plates, served as a photoreactor. The water quality parameters removal efficiency at the end of each process operation was recorded for different detention periods in the photoreactor. Water quality parameters analyzed were biochemical oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), and pH. The optimal retention time for the photoreactor was found and the BOD of the wastewater reduced to 25 from 740 mg/l (97% reduction), and TSS from 1,430 to 12 mg/l (99% reduction) for the corresponding retention time. TDS reduction efficiency was 25% and pH changed from 9.2 in raw wastewater to 8.4 in treated wastewater. Results show that the pilot treatment plant was efficient for BOD and TSS removal from the textile wastewater.

Impact of the electrode, aeration strategies, and filler material on wastewater treatment in tidal flow wetlands

The present work reports the pollutants removal performance of the waste material-based non-aerated, intermittently, and continuously aerated normal and electrode-integrated tidal flow wetlands that received municipal wastewater. The tidal flow wetlands were operated under variable wastewater contact periods. The mean biochemical oxygen demand (BOD), ammonium‑nitrogen (NH4-N), total nitrogen (TN), total phosphorus (TP), and coliform removal percentage ranges were 74–99 %, 58–87 %, 65–85 %, 62–93 %, and 56–96 %, respectively. Nutrient removals declined in all tidal flow wetlands during the longest wastewater contact period. An opposite trend was observed with organic and coliform removals. The aerated tidal flow wetlands achieved better organic and nutrient removal than the non-aerated systems. Nutrient accumulation percentage in plant tissues ranged between 0.01 and 0.7 %. Power density production within the electrode-integrated tidal flow wetlands ranged between 4474 and 8199 mW/m3. This study demonstrates the necessity of external aeration to improve the performance of the normal and electrode-integrated tidal flow wetlands.

Fabrication of semiconducting photo nano catalyst ZnO/SnO2/ CdS to cleanup the dairy wastewater in sunlight

The creation of three nanoparticles and their use in the photocatalytic degradation of organic contaminants found in dairy effluent is reported here using a sustainable and repeatable process. Physicochemical techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy dispersive X-ray, were used to characterize the materials. The photocatalytic degradation of methyl violet using three nanoparticles is investigated using a UV–Vis spectrophotometer. Solar radiation and nanoparticles were investigated to improve photocatalysis procedures. The study aimed to determine the effects of concentrated sunlight and combined catalysts on chemical oxygen demand (COD), biochemical oxygen demand (BOD), and bacterial inactivation. The concentrated sun approach achieved 90% and 95% COD and BOD removal efficiency. Comparing all the metal oxide nanoparticles, the combined nanoparticles ZnO/CdS/SnO2 demonstrate significantly better performance in the photocatalytic process. The main objective is to treat dairy wastewater for reuse for various social purposes.

Fixed-bed column sorption kinetic rates on the removal of both biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) in domestic greywater by using palm kernel activated carbon

Abstract The increasing organic loads, specifically biochemical oxygen demand (BOD5) and chemical oxygen demand (COD), in water bodies has necessitated greywater treatment before disposal. Limited studies have explored sorption kinetics of BOD5 and COD removal using activated carbon from palm kernel shell in fixed-bed columns. This study investigated continuous sorption using activated carbon from palm kernel in removing BOD5 and COD from domestic greywater. The activated carbon had a density of 0.46 g cm−3 and a surface area of 584 m2 g−1. The experiment was conducted in a 37 cm high, 2.5 cm diameter Perspex column, with varying flowrates of 5–15 mL min−1, and bed depths of 10, 15, and 20 cm. Greywater with BOD5 concentration of 251 mg L−1 and COD of 421 mg L−1 was used for this study. Effluent was collected at specified time intervals, analyzed for BOD5 and COD, and fitted to the Thomas, Yoon–Nelson, Adams–Bohart, and Bed Depth Service Time (BDST) models. The Yoon–Nelson model exhibited good agreement, as compared to Thomas and BDST while the Adams–Bohart model showed lower fit. The adsorbent demonstrated sorption capacities of 34 mg g−1 for BOD5 and 56 mg g−1 for COD, suggesting its potential for greywater treatment, particularly in BOD5 and COD removal.

Concentration of the main persistent organic pollutants in sewage sludge in relation to wastewater treatment plant parameters and sludge stabilisation

Concentration of 16 polycyclic aromatic hydrocarbons (PAHs), 7 polychlorinated biphenyls (PCBs), and 11 organochlorine pesticides (OCPs) in sewage sludge from 40 wastewater treatment plants (WWTPs) was investigated. Relationship between pollutant sludge contents, main WWTP parameters and type of sludge stabilisation was carefully evaluated. Average load of PAHs, PCBs, and OCPs in different sludges from Czech Republic was 3096, 95.7 and 76.1 μg/kg dry weight, respectively. There were moderate/strong correlations among the individual tested pollutants in sludge (r = 0.40–0.76). Relationship between total pollutant contents in sludge, common WWTP parameters and sludge stabilisation was not evident. Only individual pollutants such anthracene and PCB 52 correlated significantly (P < 0.05) with biochemical oxygen demand (r = −0.35) and chemical oxygen demand removal efficiencies (r = −0.35), suggesting recalcitrance to degradation during wastewater treatment. When sorted according to the design capacity, a linear correlation between WWTP size and pollutant contents in sludge was evident with growing WWTP capacity. Our study indicated that WWTPs with anaerobic digestion are prone to accumulate a statistically higher content of PAHs and PCBs (P < 0.05) in digested sludges compared to aerobically digested ones. The influence of anaerobic digestion temperature of treated sludge on tested pollutants was not evident.

Constructed wetland technology for the treatment and reuse of urban household greywater under conditions of Africa's Sahel region

Abstract Three pilot systems of a constructed wetland were assessed to advance the urban reuse of greywater for household gardening in areas of the world representative of Africa's Sahel (one unplanted and two planted with local species, namely Andropogon gayanus and Chrysopogon zizanioides). Principal component analysis showed planted systems provided higher removal efficiencies than the unplanted system and A. gayanus performed better for treating most water quality parameters. As expected, removal efficiencies for suspended solids (SS) and chemical oxygen demand (COD) were greater than 90% in all filters. The removal of five-day biochemical oxygen demand (BOD5) was, however, significantly greater in the filter planted with A. gayanus than in the unplanted control. For plant-beneficial parameters such as nutrients (NO3−, NO2−, NH4+, and PO43−), the removal in the planted filters was significantly higher than in the unplanted filter (&amp;gt;90% versus 73%–78%). The reduction of fecal coliforms was significantly greater in the two planted systems and exceeded 2.5 log10 removal. Analysis of the microbial water quality characteristics showed the concentration of fecal microbial indicators would achieve WHO guidelines for restricted irrigation with retention of some embedded nutrients, thus reducing pressures on areas experiencing climate variability, water scarcity, and land degradation.

Investigation of hospital wastewater treatment using the UV/H2O2/S2O8 2- process as a combined AOP method

ABSTRACT Hospital wastewater contains microorganisms, heavy metals, toxic chemicals, and different drugs that might be treated insufficiently or not at all before they enter municipal wastewater, causing numerous problems for humans and other living organisms. The aim of this study was to assess the performance of the UV/H2O2/S2O8 2- process in the treatment of hospital wastewater. This process has been modelled and optimised using the statistical response-surface method (RSM), and the regression analysis showed that the data were well-fitted with a second-order polynomial equation. Based on the model, the biochemical oxygen demand (BOD) removal efficiency can reach 93.2% in optimal conditions of pH = 3.1, H2O2 dosage of 203.1 mg/L, and NaPS dosage of 44.7 mg/L. The results showed that in the presence of both persulphate and hydrogen peroxide, the process efficiency was higher in acidic conditions and in the range of the design experiment, more oxidants had more efficiency. Turbidity, total Kjeldahl nitrogen (TKN), total organic carbon (TOC), total coliform, and E. coli were also studied as supplementary parameters, and removal efficiencies of about 78.53%, 70%, 52%, 99%, and 99.8% were achieved, respectively. Kinetic studies revealed that the data were well-fitted with the second-order kinetic model and had a regression coefficient of 0.97 and a rate constant of 0.0018 (L/mg min).