High Chemical Oxygen Demand Concentration Research Articles

Fluid dynamics and energy efficiency of submerged combustion process for treating wastewater with high salinity and COD concentration

Focusing on submerged combustion technology for the treatment of high salinity and high chemical oxygen demand (COD) wastewater, this study explores the characteristics of gas-liquid two-phase flow and heat transfer during the submerged combustion process, employing both experimental and numerical simulation methods.Consequently, the impact of essential parameters on the efficacy of submerged combustion in treating wastewater was analyzed. The experimental results show that increasing the fuel flow rate and immersion depth is beneficial to improve the temperature rise rate and shorten the evaporation time. With the increase of the organic solution flow rate and the initial COD value of the organic solution, the COD removal rate decreased, and the effect of the organic solution flow rate on the COD removal efficiency was more obvious. The use of a flat orifice plate or tapered orifice plate immersed tube structure can improve the thermal efficiency by over 10%. However, it is not conducive to the stability of the pressure in the combustor, increasing the fluctuation of the liquid level. Compared with that of traditional single-effect evaporation crystallization, the energy consumption of the submerged combustion device is decreased, and the total operation cost is reduced by 22.5%.

Enhanced Treatment of Potato Starch Wastewater Using Chitosan-Modified Biochar Film Adsorption Coupled with Ultrafiltration

Potato starch wastewater, a byproduct of potato processing, is an escalating environmental concern due to its high concentrations of COD (chemical oxygen demand), ammonia nitrogen, and total phosphorus (TP). Addressing this challenge, this research introduced a novel method combining chitosan-modified biochar film (CBC) adsorption with subsequent ultrafiltration. SEM (scanning electron microscope), FTIR (Fourier transform infrared spectral), XRD (X-ray diffractometer), and BET (specific surface area) analyses validated CBC’s enhanced surface characteristics, confirming successful chitosan (CS) film impregnation. CBC exhibited superior adsorption capacities, especially 40%wt-CBC, optimizing COD removal at 79.8%, ammonia nitrogen at 93.3%, and TP at 91.2%. Kinetic studies associated the adsorption process with a pseudo-second-order model, highlighting chemical adsorption. Additionally, the Langmuir isotherm model suggested monolayer adsorption with no inter-adsorbate interactions. The treated effluent, post adsorption, was directed through an ultrafiltration membrane, ensuring water quality suitable for reuse. This integrative treatment not only offers an effective solution for potato starch wastewater management but also underscores the potential for sustainable water resource recovery in the food processing sector.

Spatial distribution, source apportionment, and assessment of marine water quality parameters in the Bohai Sea, China

A two–year (2020−2021) survey dataset of six water quality parameters (pH, dissolved oxygen (DO), chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN), soluble reactive phosphate (SRP), and petroleum pollutants) was used to investigate their spatial distribution in the Bohai Sea and quantify their potential sources. There were significant differences in spatial distribution of the parameters. High concentrations of COD, DIN and SRP were found in three bays, with terrestrial input being the main pollution source. Phosphorus–limiting conditions were present in the Bohai Sea. High petroleum pollutant concentrations were identified in port areas, offshore oilfields, and adjacent areas. The pH was above the global oceanic average and there were no signs of acidification. The contribution of the mixed terrestrial inputs, maritime transportation, and offshore oil exploitation sources, oceanic and associated biotic sources, and seawater–atmosphere exchange and atmospheric deposition sources to water quality were 63.4 %, 8.0 %, and 28.6 %, respectively.

Spatiotemporal Nutrient Patterns, Stoichiometry, and Eutrophication Assessment in the Tieshan Bay Coastal Water, China

Land-source inputs into coastal water have increased remarkably in recent years, resulting in the deterioration of water quality, eutrophication, and algae blooms. However, we have limited understanding of spatiotemporal nutrient patterns, stoichiometry, and eutrophication assessment in Tieshan Bay coastal water at present. To investigate the rapid development of the coastal areas in Tieshan Bay in the South China Sea, nutrients and other physicochemical parameters were observed in Tieshan Bay during the normal season (April), wet season (July), and dry season (October) in 2021. The results showed that the average concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and chemical oxygen demand (COD) in Tieshan Bay are 0.071 ± 0.115 mg/L, 0.008 ± 0.013 mg/L, and 0.71 ± 0.219 mg/L, respectively. DIN/DIP ratio ranges from 9.1–69.3, with an average value of 19.9 ± 19.2, which exceeds the Redfield value, behaving P limitations. In addition, the mean eutrophication index (EI) was low in Tieshan Bay, with an average value of 0.5 ± 1.5. Moreover, the hotspot coastal water with high DIN, DIP, and COD concentrations was located in the upper half of Tieshan Bay in all seasons. In addition to the DIN, DIP, and COD contributions to EI, the average contribution rates of DIN, DIP, and COD are 26.6%, 8.8%, and 64.6%, respectively, which leads to the largest contribution of COD to EI. Furthermore, the average comprehensive index (CI) of organic pollution in Tieshan Bay surface seawater ranged from −1 to 5.6. The seawater near Hepu in S8 station has organic pollution in wet and dry seasons, and Tieshan Bay’s middle region also has slight organic pollution. Additionally, the DIN, DIP, and COD had significant relationships with salinity (p < 0.05), suggesting that coastal water quality is affected by land-based sources input. To achieve the seawater quality target and mitigate regional eutrophication, it is critical to implement land-based source management across the river-bay-coastal water continuum.

Landfill leachate treatment with a full-scale membrane bioreactor: impact of leachate characteristics on filamentous bacteria.

Bulking and foaming are extreme filamentous bacterial growths that present serious challenges for the biological leachate treatment process. The current study evaluates the performance of long-term full-scale membrane bioreactor (MBR) treating landfill leachate, specifically focusing on filamentous bacteria overgrowth in the bioreactors. The influence of the variation in leachate structure and operational conditions on floc morphology and filamentous bacteria overgrowth were analyzed for 11months of operation of the full-scale MBR system. The average chemical oxygen demand (COD) and NH4-N removal efficiencies of the system were 87.8 ± 4% and 99.5 ± 0.7%. However, incomplete denitrification was observed when the F/M ratio was low. The high C/N ratio was observed to enhance the frequency of small flocs. Furthermore, a poor to medium diversity of the microbial community was observed. Haliscomenobacter hydrossis, Microthrix parvicella, and Type 021N were found as the most numerous filamentous organisms. Paramecium spp., Euplotes spp., and Aspidisca spp. were found in small quantities. The limited concentration of PO4-P in the leachate compared to high COD and NH4-N concentrations most probably caused phosphate deprivation and increased abundance of identified filamentous microorganisms. This work is the first study in Türkiye that investigates the bulking and foaming problem in full-scale MBR that treats landfill leachate. Hence, it may provide some pioneering perspectives into landfill leachate remediation by monitoring the hybrid biological system.

Applying Eco Enzyme to Reduce Chemical Oxygen Demand (COD) Content of Artificial River Water

Eco enzyme is claimed to improve the quality of polluted water. However, the low pH of eco enzyme solutions can acidify water. The objective of this study was to investigate the effectiveness of eco enzyme in reducing the COD of river water and its effect on the pH of sterilized synthetic river water. The effect of 0.01%, 0.5%, and 1% enzyme concentrations on the COD and pH of synthetic river water with an initial COD of 240 mg/l was investigated. The results showed that eco enzyme itself has high concentration of COD and low pH. The undiluted eco enzyme increased the COD and decreased the pH of both neutralized and non-neutralized synthetic river water. At a 1% eco enzyme concentration and neutral pH, the COD increased in the beginning of experiment and had decreased only by 31.7% after 6-8 days. The COD concentration in this steady state condition had a higher value than that of the initial COD concentration in the river water. This study showed that adding only eco enzyme to synthetic river water is not effective in reducing its COD content.

Impact of Artificial Islands and Reefs on Water Quality in Jinmeng Bay, China

Recurrent green tide has been widely studied due to its severe damage to coastal ecosystem. Jinmeng Bay, a popular resort in northeastern China, has suffered from green tide events since 2015, after the constructions of artificial islands and submerged reefs. To investigate the potential impacts of artificial islands and reefs on the water quality in Jinmeng Bay, a MIKE 21 numerical model was established by coupling a hydrodynamic model with a transport model of Chemical Oxygen Demand (COD) and nitrate ion (NO3−). The changes in the water quality in Jinmeng Bay by the initial, first-stage and current construction conditions of artificial islands and submerged reefs were simulated. The model results indicated that: (1) The artificial islands and reefs in Jinmeng Bay hinder the tidal currents and weaken the tidal actions. (2) The weakened tidal actions at the estuary lead to the accretion of COD and NO3−. The neap tides generate a littoral zone with the high concentration of COD and NO3−, and the spring tides maintain the zone at the estuary. (3) NO3− is more sensitive than COD to the variation of hydrodynamic conditions. The NO3− concentration in the north of Conch artificial island is altered significantly, where the construction of the artificial structures decrease the concentration by ~30%, while the demolition of the connection road increases the concentration beyond its initial values by 16~21%. (4) Under the current construction conditions, the rising concentrations of COD (up to 2%) and NO3− (up to 40%) increase the frequency and scale of green tides in Jinmeng Bay considerably. Therefore, continuous monitoring of water quality is required for this region.

Efficient carbon removal and excellent anti-clogging performance have been achieved in multilayer quartz sand horizontal subsurface flow constructed wetland for domestic sewage treatment

The present study aimed to investigate the application of a multilayer quartz sand substrate horizontal subsurface flow constructed wetland (HSFCW) for campus sewage treatment. It aimed to assess the pollutant removal efficiency and anti-clogging performance under the suggested maximum organic loading rate (250 g/m2/d). The results of the multilayer HSFCW (CW6) were compared to the mololayer HSFCW (CW1) for the removal of the chemical oxygen demand (COD), solid accumulation, and microbial communities. During operation, the combination conditions of high hydraulic loading rate (HLR) with low COD concentration were better for COD removal under a high organic loading rate (OLR) of 200–300 g/m2/d. The maximum removal rate reached 80.4% in CW6 under high HLR, which was 13.8% higher than that in CW1, showing better adsorption and biodegradation ability of organic matter. Impressive clogging resistance capacity was found in CW6 due to the lower contents of the insoluble organic matter (IOM) that are prone to clogging, indicating full degradation of organic matters, particularly IOM, in CW6 under high HLR. Less abundance of unclassified Chitinophagaceae (under low HLR), Pedobacter and Saccharibacteria_genera_incertae_sedis (under high HLR) in CW6, which contributed to aerobic membrane fouling, helped to prevent clogging. Moreover, Brevundimonas, Cloacibacterium, Citrobacter, Luteimonas contributed to IOM degradation, thus further enhancing the anti-clogging performance. In view of the better clogging resistance performance, the application of CW6 operated under high HLR and low COD concentrations was recommended to achieve economical, efficient, and steady COD removal for domestic sewage treatment in long-term operation.

Feasibility of Bio-Coagulation Dewatering Followed by Bio-Oxidation Process for Treating Swine Wastewater.

The unsatisfactory performance of the conventional swine wastewater treatment is drawing increasing attention due to the large amount of refractory chemical oxygen demand (COD), nitrogen, and phosphorus attached to the suspended solids (SS). In this study, for the first time, a novel process based on bio-coagulation dewatering followed by a bio-oxidation (BDBO) system was developed to treat swine wastewater containing high-strength SS, COD, TN, and TP. Firstly, after the bio-coagulation process, the removal efficiencies of SS, COD, NH3-N, and TP reached as high as 99.94%, 98.09%, 61.19%, and 99.92%, respectively. Secondly, the filtrate of the bio-coagulation dewatering process was introduced into the subsequent bio-oxidation process, in which the residual COD and NH3-N were further biodegraded in a sequence batch reactor. In addition, the dewatering performance of the concentrated swine slurry was substantially improved, with the specific resistance to filtration decreasing from 17.0 × 1012 to 0.3 × 1012 m/kg. Moreover, the concentrated swine slurry was pressed and filtered into a semi-dry cake after pilot-scale bio-coagulation dewatering treatment. Finally, the concentrations of COD and NH3-N in the effluent after the BDBO process, ranging between 150-170 mg/L and 75-90 mg/L, met the relevant discharge standard. Compared to traditional treatments, the BDBO system has excellent large-scale potential for improving the treatment efficiency, shortening the operation period, and reducing the processing costs, and is emerging as a cost-effective alternative for the treatment of wastewater containing high concentrations of SS, COD, TN, and TP.

Assessment of the water quality of the Niger River in Bamako, Mali, based on the Water Quality Index

Abstract The Niger River, threatened by human activities, is the main drinking water source for the population of Bamako city. This study assesses the trend of Niger River pollution in Bamako using the Water Quality Index (WQI). Fourteen parameters, namely Turbidity, Potential of Hydrogen (pH), Electrical Conductivity, Dissolved Oxygen, Total Dissolved Solids, Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Nitrate, Nitrite, Ammonium, Phosphate, Sulphate, Chloride and Copper, were employed to characterise the Niger River water quality during the period from 2016 to 2020. Parameters were measured at 15 sampling locations. High values of Turbidity, pH and high concentrations of BOD5, COD, Nitrite, Ammonium and Phosphates were recorded. The results showed that the Niger River water quality was good for 4 months and poor for 5 months during the dry season in a low flow period. Moreover, the water quality was poor during the 3 months of the wet season in the high flow period. The calculated WQI average values ranged from 75 to 100, indicating very poor water quality from upstream to downstream of Bamako city. Therefore, the Niger River water is polluted and cannot be used for drinking or industrial uses without any treatment.

Electrocoagulation followed by sound agitation for removal of nitrogen and carbon-based pollutants from industrial wastewater.

The herculean imprecation of nitrogen-based pollutant like ammoniacal nitrogen (AN) and chemical oxygen demand (COD) on aquatic milieu is now a concern for the dye, pharma and fertiliser industries. Wastewater from these is characterised with high concentration of AN, COD and total dissolved solids (TDS), treatment of which is of utmost importance for a cleaner environment. In the current research work, an attempt was made to apply integrated electro-coagulation (EC) - sonication process for the removal of COD and AN from highly acidic dye intermediate wastewater containing high to very high concentration of COD and AN. Systematic laboratory experiments were conducted for the treatment of dye intermediate wastewater and influences of pH (5-11), applied voltage (0.5-4V) and electrolysis time (30-120 min) were investigated. A Response Surface Methodology (RSM) was used for optimization of major operating parameters for EC. The conditions for minimum fraction remaining (C/C0), was found to be same for both COD and AN, i.e. pH 7, time 90 min and applied voltage 2V. The C/Co value for COD and AN were 0.244 and 0.302, respectively. The C/Co value of COD and AN in combined EC-Sonication process with optimum operating conditions were 0.145 and 0.228 respectively with sonication time 60 min at a frequency of 33 kHz. Thus, EC - sonication process is an efficacious process for their removal from dye industrial wastewater.

Recovery of Acid and Alkaline from Industrial Saline Wastewater by Bipolar Membrane Electrodialysis under High-Chemical Oxygen Demand Concentration

Actual high saline wastewater containing concentrated organics and sodium chloride is a bioenergy and renewable resource. This study compared two different bipolar membrane electrodialysis membranes from two companies' stacks to recover HCl and NaOH from sodium chloride solution and actual chemical wastewater. The results demonstrated that the electrolysis rates were around 1.5 kg/m2h, the HCl and NaOH production rates were about 0.9 kg/m2h, energy consumption was in the range of 1.05-1.27 kWh/kg, and the economic benefits were above 1 yuan/h in BMED systems. From analyzing the performance of seven different BMED membrane stacks, the B2 stack was chosen for electrolyzing actual high salt wastewater to observe the effect of chemical oxygen demand on BMED systems, where electrolytic salt performance, HCl-NaOH alkali production rates, and energy consumption show linear dependence on time for 5000 mg/L chemical oxygen demand wastewater. It illustrated chemical oxygen demand can enhance energy consumption and reduce electrolytic salt performance and the acid and alkali production rates, due to improving the membrane area resistance. In this study, the effect of high COD saline wastewater on the performance of a BMED membrane stack was clarified and the mechanism was analyzed for its practical application in treating chemical high salt wastewater.

Adsorption of Organic Compounds in Leachate using Precipitated Calcium Carbonate (PCC) from Ale-Ale Shells

Leachate waste from piles of garbage in the landfill (TPA) has a high concentration of Chemical Oxygen Demand (COD). High COD concentrations can cause a decrease in dissolved oxygen concentrations in the waters. Simple leachate treatment is carried out using the adsorption method with adsorbents derived from food waste. This research used Precipitated Calcium Carbonate (PCC) adsorbent from ale-ale shells. This study aims to evaluate the effect of particle size and calcination temperature variations on PCC yield and analyze the adsorption ability of PCC adsorbents in reducing COD concentrations. In addition, PCC was characterized using an infrared spectrophotometer (FTIR) and an X-ray diffractometer (XRD). Determination of COD concentration was carried out by permanganometric titration. The optimum PCC yield of 57.75% was obtained from Ale-ale shells with a particle size of 40 mesh with a calcination temperature of 800 ° C. The functional groups in PCC are C-O at wave numbers 1403 cm -1 , 873 cm -1 , and 713 cm -1 . XRD characterization showed the presence of a calcite phase with a high peak intensity at 2 = 29.38 ° . The adsorption of organic matter on leachate by PCC (4.5 g/50 mL) with a stirring speed of 200 rpm for 240 minutes reduced the COD concentration of leachate from 1131.28 mg/L to 456.94 mg/L with an adsorption efficiency of 59.61% .

Influence of iron species on the simultaneous nitrate and sulfate removal in constructed wetlands under low/high COD concentrations

Nitrate and sulfate are crucial factors of eutrophication and black and odorous water in the surface water and thus have raised increasing environmental concerns. Constructed wetlands (CWs) are the last ecological barrier before effluent enters the natural water body. To explore the simultaneous removal of nitrate and sulfate, the CW microcosms of CW-Con (with quartz sand), CW-ZVI (quartz sand and zero-valent iron), CW-Mag (quartz sand and magnetite), CW-ZVI + Mag (quartz sand, ZVI and magnetite) groups were set up under the low (100 mg/L)/high (300 mg/L) chemical oxygen demand (COD) concentration. Under the high COD condition, CW-ZVI group showed the best performance in nitrate (97.1%) and sulfate (96.9%) removal. Under the low COD concentration, the removal content of nitrate and sulfate in CW-ZVI group was better than CW-Mag group. The reason for this result was that zero-valent iron (ZVI) could be the electron donor for nitrate and sulfate reduction. Meanwhile, ZVI promoted chemical denitrification under high COD concentration according to PCA analysis. In addition, the produced sulfides inhibited the relative abundance of denitrifying bacteria, resulting in the lowest nitrate removal rate in CW-Mag group with sufficient electron donors. This study provided an alternative method to enhance simultaneous sulfate and nitrate removal in CWs.

Characterization of Solid Waste Leachateand Its Impact on Surface Water Quality: A Case Study at Rajbandh, Khulna, Bangladesh

The present study was carried out to characterize leachate from waste dumping site and its impact on surrounding surface water quality at Rajbandh in Khulna. For this purpose, surface water samples (10) and leachate samples (5) were taken from the site during two season the monsoon season and post monsoon respectively. The samples were taken during the daytime from 9 a.m. to 1 p.m because at midday the temperature rises and the physico-chemical parameters of the water are modified. Some physico-chemical parameters such as pH, Electrical conductivity (EC), Total dissolved Solids (TDS), Dissolve Oxygen (DO), Chloride (Cl-), Magnesium (Mg2+), Calcium (Ca2+), Sodium (Na+), Potassium (K+), Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Iron (Fe2+), Phosphate (PO43-), Sulfate (SO42-), Nitrate (NO32-) were analyzed in the laboratory in accordance with standard laboratory procedure. As well as some heavy metals such as Cadmium, Chromium, Lead, Manganese, Iron and Zinc were also analyzed in the laboratory. It is observed that, the physicochemical characteristics of surface water and leachate samples vary among the parameters in two seasons throughout the study period. The concentration of TDS and EC were found to be high in leachate compare to surface water samples that might be caused due to the existence of high-level various anions and soluble salts with other inorganic components. In monsoon the TDS values ranged from 3227 ± 2357 for leachate and 737 ± 498 for surface water samples whereas in post-monsoon the variation followed by 4640 ± 1790 and 803 ± 232 for surface water and leachate respectively. In case of EC for leachate it varied from 3630 ± 1397 and 4900 ± 1734 for monsoon and post-monsoon seasons correspondingly but varied from 1473 ± 498 in monsoon and 1627 ± 473 in post-monsoon for surface water samples. The high concentration of BOD (3.91 ± 1.54 in monsoon and 6.25 ± 3.27 in post- monsoon) and COD (117.80 ± 58.31 in monsoon and 229.39 ± 166.55 in post-monsoon) value were found in surface water samples compared to leachate samples. In case of Cr for leachate it varied from 0.081 ± 0.029 and 0.070 ± 0.026 for monsoon and post-monsoon seasons correspondingly. As well as the concentration of Cd (0.023± 0.006 in monsoon and 0.087±0.068 in post monsoon) and Pb (0.35±0.109 in monsoon and 0.025±0.013 in post monsoon) varied greatly during both season. The concentration of heavy metals such as Pb, Zn, Cr and Mn in surface water samples was also greater than 0.001mg/l. Further for leachate COD was very strongly correlated with TDS and cadmium. Magnesium was significantly correlated with potassium. For surface water sample TDS was significantly correlated with EC and pH. Chloride was significantly correlated with Cd and pb was correlated with calcium. This study recommended that the authority should take proper steps for the management of waste as well as give emphasis on the leachate collection.

Remediation of Organic Contaminant in Sludge by using Bioaugmentation and Solidification and Stabilization (S/S) Method

Fiberboard industrial wastewater sludge is a type of waste produced as a by-product of the wastewater treatment plant, which consists of organic matters that can turn into toxic and hazardous forms if left untreated. Hence, this study aims to remediate the sludge by using fungi bioaugmentation and solidification and stabilization (S/S) method in 7 days. This study focus on the degradation of organic contaminants based on leaching behaviour of Chemical Oxygen Demand (COD). Besides, the compressive strength was also measure for safe disposal. Aspergillus brasiliensis ATCC 16404 was used for fungi bioaugmentation of sludge and Portland cement was used as the binder in the S/S method. After a week, bioaugmentation method shows the lowest COD concentration (467mg/L). Whereas, higher COD concentration was detected for S/S method (550 mg/L). By using both methods, COD concentration was detected highest (570 mg/L) than single method. Since both methods were less successful in removing COD, it is highly recommended to conduct in longer duration for future work.

Environmental Impact Assessment Study for Shatt Al-Arab River Receiving Industrial Wastewater

Shatt Al-Arab river has been used as the raw material for the drinking water, irrigation and fish purposes in Basrah city. Concurrently, this river has been polluted by domestic, farming and industrial waste. Three main factories lie on the bank of Shatt Al-Arab river: Al-Hartha Paper Mill, Hartha Power Station and Al-Najibia Power Plant. All these consume water from the river and return their wastewater back to it. The aim of this study is to assess the water quality of Shatt Al-Arab river and its suitability for drinking, irrigation and aquatic life through physicochemical analysis temperature, pH, EC, Total Dissolve Solid (TDS), Cl−, Na+, K+, Ca+2, Mg+2, HCO3 total hardness, Biological Oxygen Demand (BOD5), Dissolved Oxygen (DO), Chemical Oxygen Demand (COD). BOD5 concentration near factories showed polluted water, unsafe and requiring costly treatment to use for drinking water. Sodium concentration is a key factor for irrigation, which represent by SAR and SSP. As SSP exceed 75.73 % in water near these factories, this could breakdown soil structure and can damage agriculture area. The high concentrations of BOD5 and COD could pose a threat to aquatic life and fishes. As Shatt Al-Arab river is used for different purpose, the result in this study showed polluted water near industrial areas. Therefore, it is recommended to have regular data on water quality for this river near these areas.

Biological treatment of produced water: A comprehensive review and metadata analysis

A metadata analysis was conducted to analyze the impact of several operating conditions on the biological removal of chemical oxygen demand (COD) from produced water (PW). Operating conditions including temperature, salinity, oxygen availability, treatment technology, microorganism type, and treatment scale were investigated. No limiting maximum COD elimination capacity was reported in the literature, signaling the need to experiment with higher COD concentrations at reduced retention times to identify if such a limit exists. The maximum recorded COD elimination capacity of PW was achieved under low salinity and aerobic conditions in a membrane bioreactor using oil-degradation bacteria on a laboratory scale. Suspended growth exhibited maximum COD removal efficiency, and membrane bioreactors were the most studied technique and achieved the highest performance. Superior COD removal efficiency was realized under hypersaline conditions; however, the COD removal efficiency under freshwater conditions was higher than that under hypersaline conditions.

Simulating the impact of piers on hydrodynamics and pollutant transport: A case study in the Middle Yangtze River.

It is known that channel engineering, including the construction of piers, will change the river hydrodynamic characteristics, which is a significant factor affecting the transport process of pollutants. With this regard, this study uses the well-validated and tested hydrodynamic module and transport module of MIKE 21 to simulate the hydrodynamics and water quality under various pier densities in the Wuhan reach. Hydrodynamic changes around the piers show spatial differences, which are similar under different discharges. The range and amplitude of hydrodynamic spatial variations increase with the increase in pier density. However, there is a critical value of 1.25 to 2.5 units/km. When the pier density is less than this critical value, this type of cumulative effect is the most significant. Additionally, greater changes can be found in chemical oxygen demand concentrations, which also show spatial and temporal variations. The area with high chemical oxygen demand concentration upstream and downstream from the engineering area exhibits the distribution characteristics of “decrease in the downstream area and increase in the upstream area” and “increase in downstream the area and decrease in the upstream area” respectively. In the reach section of the engineering area, the area with high chemical oxygen demand concentration increases in the front area near the piers and decreases near the shoreline. Furthermore, the concentration shows attenuation actions with a longer residence time owing to the buffering effect of pier groups. These results have significant implications on shoreline planning and utilization. Moreover, they provide scientific guidelines for water management.

New Technology for Degradation of Wastewater Containing High Concentrations of COD and Boron Based on Manganese-Iron Oxide Catalytic Support

The existing methods for simultaneous treatment of wastewater containing high concentrations of chemical oxygen demand (COD) and boron are too cumbersome and require a relatively long treatment time. The traditional oxidation method is easy to cause a large amount of sludge and other secondary pollution. Therefore, in this research, the wastewater was oxidized by the self-synthesized manganese-iron oxide catalytic support. This oxidation and adsorption combined method significantly increased the efficiency of wastewater treatment, reduced the treatment time and the replacement frequency of consumables. The efficiency in degradation of high-concentration COD (25,250 mg/L) was more than 90%, which could be reached within 40 min, while that of boron (500 mg/L) could reach above 95% within 20 min. After optimization of the parameters (daily treatment capacity: 5CMD) was combined to treat high-concentration wastewater containing high concentrations of COD (14,700 mg/L) and boron (486 mg/L), with treatment efficiency approaching 100% within 20 min. As proved by the research results, after being treated by the new manganese-iron oxide catalytic support and activated carbon, the wastewater has reached the emission standard and can be discharged directly. This combined method provides a new way for the treatment of wastewater containing high concentrations of COD and boron.