Chemical Oxygen Demand Concentration Research Articles

Pretreatment of palm oil mill effluent (POME) for Spirulina cultivation

Palm Oil Mill Effluent (POME) is liquid waste produced from palm oil processing. The quantity of POME in Indonesia has increased from year by year. POME is not a toxic material, but it will be very dangerous if it is thrown directly without pre-processing, because it will harm the aquatic ecosystem due to its high content of COD (Chemical Oxygen Demand) and BOD (Biological Oxygen Demand). POME has also a high content of nitrogen (N) and phosphor (P), which make POME can be used as medium for microalgae growth. Therefore, this research is aimed to study pretreatment and to utilize its nutrient content (N, P) for medium of spirulina growth. Pretreatment of POME research was conducted by using two stage of cultivation (Chlamydomonas and Chlorella) and dilution factor (0-4x). The result of this pretreatment was then used for Spirulina growth. Spirulina cultivation was conducted by nutrient addition and without nutrient addition. This research showed that the best performing variation of dilution rate to cultivate Spirulina is 4x dilution. It showed that 4x dilution could reduce COD content until 128.33 mg/L. Besides that, in 4x dilution, microalgae as Chlamydomonas, Chlorella, and Spirulina had the highest growth rate as compared to 2x dilution and without dilution. The best wild algae for pretreatment of POME is Chlorella. Because by using wild algae Chlorella, COD content could be reduced until 128.33 mg/L and achieve the lowest COD content compared with Chlamydomonas. For microalgae growth, addition of nutrient is better than without nutrient, because nutrient could enhance Spirulina photosynthesis.

Roof runoff pollution control with operating time based on a field-scale assembled bioretention facility: Performance and microbial community dynamics

Bioretention facilities are essential, low-impact development measures to treat roof runoff pollution. To explore the effects of roof runoff pollution control and internal influencing mechanisms of field-scale bioretention facilities, a newly assembled bioretention facility (ABF) comprising volcanic rock and coconut coir was constructed. The results of the 21-month experiment showed that the peak concentrations of total suspended solids (TSS), ammonia nitrogen (NH4+–N), and chemical oxygen demand (COD) of roof runoff were 332.50 mg∙L−1, 3.46 mg∙L−1, and 122.33 mg∙L−1, respectively, indicating that the roof runoff was seriously polluted and needed urgent treatment. The removal rates of TSS, NH4+–N, and COD within the facility were 86.50 ± 7.31 %, 79.40 ± 19.28 %, and 51.84 ± 26.24 %, respectively. However, continuous and high-intensity rainfall decreased pollutant removal performance by weakening the adsorption effect of the media. Continuous pollutant input decreased the abundance of Arthrobacter and Hyphomicrobium within the media, and functional bacteria, such as KD4–96, Roseiflexaceae, Vicinamibacteraceae, and Gaiellales, played dominant roles in NH4+–N and COD removal to ensure the long-term stability of the facility. This study provides theoretical guidance and a practical basis for enhancing the application of ABF in mitigating roof runoff pollution.

Enhanced microalgal hydrogen production subsisting on visible light TiO2 nanotubes photocatalyst pre-treated palm kernel expeller

The present study investigated the application of photocatalytic process using TiO2 nanotubes (NTs) photocatalyst as an effective pre-treatment method for palm kernel expeller (PKE) in increasing its biodegradability to enhance the microalgal hydrogen production via dark fermentation. A series of TiO2 NTs photocatalysts were synthesized via employing electrochemical anodization of Ti foil at various voltages each in different types of electrolytes (choline chloride-ethylene glycol (ChCl-EG), choline chloride-urea (ChCl-U), choline chloride-glycerol (ChCl-Gly)). Increasing trend of average NTs diameters at 26.14 ± 1.30, 73.01 ± 1.94 and 122.00 ± 13.32 nm was observed for 25, 30 and 35 V in synthesizing TiO2 NTs using suitable ChCl-EG electrolyte, respectively. The high 35 V had resulted in noticeable pore ruptures within this TiO2 NTs photocatalyst. The PKE pre-treated by TiO2 NTs photocatalyst anodized at optimum 30 V in ChCl-EG electrolyte had demonstrated the highest releases of biochemical oxygen demand (BOD5) and soluble chemical oxygen demand (SCOD) concentrations at 594 and 607 mg/L, respectively. Moreover, the microalgal efficiency of BOD5 conversion and hydrogen yield were also consistently maintained from third cycle of TiO2 NTs photocatalyst's reutilizations, signifying the stability of TiO2 NTs photocatalyst.

Study on the evaluation system and risk factor traceability of receiving water body

Abstract The risk factor of the receiving water body is one of the important factors that affect the self-purification ability of the water body. Analyzing the concentration and removal rate of the target substances such as suspended solid (SS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in the receiving water body during the life cycle can trace the risk factor. Based on this, this article takes a sewage treatment plant and its receiving water body in Nanjing as the research object, sets up five sampling points, and calculates the target concentration and removal rate using the cellular automata-Markov chain Monte Carlo method. Thus, risk assessment of water bodies can be achieved. The results show that: (1) the concentration of the target substance in each process stage has obviously decreased during the life cycle, with an average concentration of 3–18 mg/L; (2) in the life cycle, the highest removal rate of target concentration in each process section can reach 85%; (3) the concentration of target substances SS, COD, TN, TN, TP, and TP at the outlet of the sewage treatment plant is relatively high. Practice has proven that this research method can assess the risk factors of receiving water bodies, so as to improve the scientific, refined and standardized environmental management.

Effect of predatory bacterial mixtures on biolysis of waste activated sludge to improve dewatering performance

ABSTRACTThe generation of surplus sludge during biological wastewater treatment has become a prevalent issue, necessitating the development of a dewatering approach that is efficient, economically feasible, and ecologically sound. Bdellovibrio-and-like-organisms (BALOs) are obligatory parasitic bacteria that prey on an array of bacteria. In this study, different BALO strains were isolated and purified from waste activited sludge (WAS). Anti-predation host strains were applied to screen the BALO strains with different host-range to minimize the overlap of the biolysis prey spectrum. In addition, the BALO strains with different host preferences were mixed for sludge biolysis treatment efficiency comparison. The results indicated that the capillary suction time and the bound water content in the WAS treated with the mixed BALOs were significantly decreased by 25.9% ± 1.7% and 5.2% ± 1.2%, respectively, compared to those treated with the single BALO strain. The soluble chemical oxygen demand concentration in the mixed BALOs treated group was increased by 31.2% ± 0.7% than that treated with the single strain. The findings indicate that the mixed strains used in the treatment process resulted in a notable enhancement of both sludge dewatering performance and lysis degree. In addition, the abundance of Proteobacteria treated with the BALO mixtures decreased by 69.1% than the single strain treated one which demonstrated that the BALO mixture expanded the sludge host lysis spectrum. This study revealed the different effects of single and mixed strains on sludge community structure, suggesting that the BALO host-range expansion is crucial to further improve sludge dewatering performances.

Depuration of landfill leachates using fly ash as a catalyst in solar advanced oxidation processes and a compost bioreactor

Fly ash (FA) is a problematic solid waste coming, for instance, from coal combustion. Herein, FA is used in a solar photocatalytic system to deal with landfill leachates (LL), which is another challenging waste. The photocatalytic process is combined with coagulation-flocculation pretreatment and a compost-based biological post-treatment. FA was characterized initially, showing silicon dioxide (52.25%), aluminum oxide (36.99%), calcium oxide (6.92%), iron oxide (2.47%), and titanium dioxide (1.74%), as the main composing oxides. Also, FA had a low surface area (0.48 m2/g), and high thermal stability (<2% of weight loss at 1000 °C). At the same time, the characterization of LL indicated this is a very polluted liquid, due to its high content of chemical oxygen demand (COD, 8072 mg/L), humic acids (HA, 7320 absorbance at 254 nm), iron (3.1 mg/L), copper (258 mg/L), and a slightly basic pH (8.5). After the coagulation-flocculation pretreatment, the supernatant liquid was submitted to the photocatalytic process (FA/H2O2/sunlight), which removed ∼70% of COD. For the photocatalytic system, the effects of pH, H2O2 concentration, and FA dose were assessed; evidencing that the pH change from 3.0 to 6.0 affected the COD and HA removals strongly. Under proper operating conditions (i.e., FA: 2.0 g/L, H2O2: 2000 mg/L, and pH: 3.0), the photocatalytic process significantly decreased the sample toxicity (∼56%). Thereby, the resultant sample from the FA/H2O2/sunlight system was submitted (for 10 days) to the action of the compost-based biotreatment, comparing the use of non-adapted and adapted aerobic microorganisms. The adapted microorganisms exhibited a higher action, achieving removals of ∼68% and ∼9% for the metals (Fe and Cu) and COD, respectively. The results of this research work demonstrated the good suitability of FA-photocatalysis combined with a coagulation-flocculation pre-treatment and a compost-based biological post-treatment to face problematic landfill leachates.

Impact of waste separation on the biological nitrogen removal in a MSW incineration leachate treatment plant: Performance and microbial community shift

After waste separation program was launched in China in 2019, incineration leachate treatment plants are facing a challenge of effective removal of nitrogen from leachate due to lack of sufficient carbon source. In this study, the performance of a biological incineration leachate treatment process (anaerobic digestion (AD) - two-stage anoxic/aerobic (A/O) process) was evaluated after adopting the waste separation program, and the changes in the microbial community and function was analyzed using 16S rRNA amplicon sequencing technology. Results showed that after the waste separation, the influent chemical oxygen demand (COD) concentration reduced by 90% (from 19,300 to 1780 mg L−1) with the COD/N ratio decreased from 12.3 to 1.4, which led to a decreased nitrogen removal efficiency (NRE) of <65% and a high effluent NO3− accumulation (445.8–986.5 mg N·L−1). By bypassing approximately 60% of the influent to the two-stage A/O process and adding external carbon source (glucose), the mean NRE increased to 86.3 ± 7.4%. Spearman's analysis revealed that refractory compounds in the bypassed leachate were closely related to the variations in bacterial community composition and nitrogen removal function in the two-stage A/O, leading to a weakened correlation of microbial network. KEGG functional pathway predictions based on Tax4Fun also confirmed that the bypassed leachate induced xenobiotic compounds to the two-stage A/O process, the relative abundance of nitrogen metabolism was reduced by 32%, and more external carbon source was required to ensure the satisfactory nitrogen removal of >80%. The findings provide a good guide for regulation of incineration leachate treatment processes after the waste separation.

Characterizing and optimizing adsorption for olive mill wastewater processing in Loukkos, Morocco.

The present research consists of studying the characterization and treatment of the olive mill wastewater (OMWW) resulting from the olive industries of the region of Loukkos, Morocco. According to the national plan for green Morocco, the annual volumes of OMWW discharges increase with the expansion of the areas of olive plantations compared to agricultural activities. The study of the organic, mineral, and microbiological composition of the obtained OMWW showed that they are rich in microbiological (FMAT, Let M., and B.L.), mineral (total Kjeldhal nitrogen, orthophosphate, total phosphorus, sodium, potassium, calcium, copper, iron, zinc, manganese, and lead ions), and organic (COD, BOD5, and polyphenols) micropollutants with very high percentages that are higher than the standards in force. The treatment used in this study is the combined process of aerated lagooning/adsorption using powdered activated carbon after optimization of the experimental parameters (mass concentration of activated carbon (AC) and agitation rapidity (Ar)) by experiment design method. The obtained physicochemical parameters, such as pH, total suspended solids (TSS), chemical oxygen demand (COD), rate of discoloration, and polyphenol content of raw OMWW, were 4.87, 0.63, 80.3, 0.8, and 1.45 g/l, respectively. The results of these parameters for the treated OMWW were obtained in the order of 6.10, 0.22, 28, 0.28, and 0.44 g/l for pH, TSS, COD, discoloration rate, and polyphenol content, respectively. These results show that the proposed treatment significantly reduced acidity, TSS, COD, discoloration rate, and polyphenol contents, with a performance of about 25.26, 65, 65.13, 65, and 69.65%, respectively. This indicates that there is significant performance in the processing of exploited OMWW.

Coconut husks as a packing media in anaerobic filters for the treatment of septic tank effluent in Tonga

Septic tanks can become overloaded overtime due to increases in the size of households or the build-up of sludge. This results in the wastewater spending less time within the tank and therefore a reduced level of treatment. One solution to enhance treatment is to add an anerobic filter after the existing septic tank. The anaerobic filter requires media for the establishment of a biofilm and the use of coconut husks were identified as a possibility due to their abundance. Both green and brown coconut husks were imported from Tonga and tested in laboratory scale anerobic filters treating synthetic wastewater. The treatment performance was monitored in terms of the chemical oxygen demand (COD) which is a measure of organic strength. There was also potential for organic material to leach out of the coconut husks so additional testing was done to evaluate this. It was found that four times more COD was leached from the green coconut husks showing that brown coconut husks were the better choice. The brown coconut husk reactor reduced the COD concentration by 49%. This study has indicated that there is value in examining the feasibility of implementing an anaerobic filter using brown coconut husks to enhance wastewater treatment from septic tanks. Further research should focus on examining whether any nutrients are released from the husk and then practical considerations such as the scale needed for a household and maintenance requirements.

A pilot-scale electrocoagulation-treatment wetland system for the treatment of landfill leachate

In the present study, the technical feasibility of an electrocoagulation-treatment wetland continuous flow system, for the removal of organic matter from landfill leachate (LL), was evaluated. The response surface methodology (MSR) was used to assess the individual and combined effects of the applied potential and distance between electrodes, on the removal efficiency and optimization of the electrocoagulation process. The hybrid treatment wetland system consisted of a vertical flow system coupled to a horizontal subsurface flow system, both planted with Canna indica. For a chemical oxygen demand (COD) concentration - without pretreatment of 5142.8 ± 2.5 mg L−1, the removal percentage for the electrocoagulation system was 79.4 ± 0.16%, under the optimal working conditions (Potential: 20 V; Distance: 2.0 cm). The COD removal efficiency in the treatment wetland with Canna indica showed a dependence with the hydraulic retention time, reaching 59.2 ± 0.2 % over 15 days. The overall efficiency of the system was about 91.5 ± 0.02 % removal of COD. In addition, a decrease in the biochemical oxygen demand (94.8 ± 0.14%) and total suspended solids (88.2 ± 0.22%), also related to the contamination levels of the LL, were obtained. This study, for the first time, shows that the coupling of electrocoagulation together with a treatment wetland system is a good alternative for the removal of organic contaminants present in LL.

Ozone combined with mechanical agitation to enhance sludge cell lysis and provide an alternative carbon source for nitrogen removal of bioreactors

The activated sludge method results in the production of significant amounts of excess sludge. Moreover, biological nitrogen removal requires an external carbon source, which presents environmental and economic challenges. To address these challenges, this study combined ozone with mechanical agitation to achieve sludge cell lysis. Through both experiments and COMSOL Multiphysics simulations, optimal conditions were identified. These conditions include a six-bladed disk turbine stirrer speed of 800 rpm, an ozone concentration of 40 mg/L, and an ozone dose of 100 mg·g−1 MLSS (Mixed Liquid Suspended Solids). Notably, the sludge solubilization efficiency improved by 20.1 % when compared to using ozone alone. After the sludge dissolution, this paper observed elevated concentrations of soluble chemical oxygen demand (SCOD), total nitrogen (TN) and total phosphorus (TP) in the supernatant, reaching 3126 mg/L, 144.3 mg/L, and 49.6 mg/L, respectively. This study also investigated the feasibility of using this supernatant as an external carbon source in a sequencing batch reactor. The results showed that while the supernatant had minimal impact on COD removal, it significantly enhanced nitrogen removal. Compared to using glucose as an external carbon source, the TN removal rate increased by 16.9 %. However, TP removal was inhibited.

Technology Selection for Wastewater Treatment in the Maldives

In the Maldives, the discharge of untreated wastewater into the sea poses a significant threat to public health and the marine environment. This study proposes technically feasible, sustainable, and economical wastewater treatment technologies appropriate for small islands in the Maldives. Out of the 187 residential islands in the Maldives, three islands (HA. Dhidhdhoo, HA. Hoarafushi, and HA. Ihavandhoo) were selected as study areas. This study characterized the wastewater from these islands using physiochemical and microbiological water quality assessment parameters. The Water and Wastewater Treatment Technologies Appropriate for Reuse (WAWTTAR), an open-source software developed by the Humbolt State University in 1993, was used to simulate the performance of different wastewater treatment processes to treat the characterized wastewater. The feasible alternatives identified from these simulations were analyzed using a Multi-Criteria Analysis (MCA), considering various indicators that influence the decision-making process. The wastewater quality assessment revealed that the wastewater generated in the three islands produced low concentrations of chemical and biological oxygen demand (COD and BOD), with concentrations ranging from 267 – 309 mg/L and 128 – 219 mg/L, respectively. Nitrate and phosphate concentrations were also low (5.7 – 18.0 mg/L and 2.8 – 14.9 mg/L, respectively), where these concentrations in Dhidhdhoo and Hoarafushi were already within the maximum allowable limits of 15 mg/L and 10 mg/L, respectively, for discharge into the deep sea. Based on the findings, secondary treatment technologies such as membrane bioreactors (MBR) and sequencing batch reactors (SBR) with Ultraviolet (UV) disinfection were found to be the most feasible options for treating the wastewater. These results were further checked for robustness using a sensitivity analysis. This study demonstrates that the proposed methodology is suitable for technology selection and can provide valuable information for policymakers and stakeholders in the country and serve as a basis for future studies.

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.

Effects of Surface-Wave-Sustained Argon Plasma Torch Interaction with Liquids

In this paper, an investigation of the interaction of a surface-wave-sustained argon plasma torch with liquids is presented. The plasma is produced by an electromagnetic wave traveling along the plasma–dielectric interface, and at the same time, the plasma is a part of this waveguide structure. Because the interaction of the plasma torch with water (liquid) results in modifications of the properties of both the treated water and the plasma itself, a detailed study of the effects in both media is required. The results of the experimental investigation of a surface-wave-sustained argon plasma torch interaction with liquids show significant changes in the plasma parameters, such as the electron excitation temperature Te and the average rotation temperature Trot. In addition, mechanical waves are produced both in the meniscus surface and in the plasma torch by the interaction between the plasma torch (ionized gas with charged particles and electric field) and the liquid surface, which is different from the effects produced by a neutral gas jet on a liquid surface. As a result of the plasma–water interaction, the water’s chemical and physical characteristics, such as the water conductivity, pH, and H2O2 concentration, are modified. As a possible application for water purification, the performed SWD treatment of model wastewater shows a significant variation in nitrate, ammonium, phosphate, and COD (chemical oxygen demand) concentration as a result of the treatment.

Rapid static feeding combined with Fe2+ addition for improving the formation and stability of aerobic granular sludge in low-strength wastewater

Aerobic granular sludge (AGS) needs a long start-up time and always shows unstable performance when it is used to treat low-strength wastewater. In this study, a rapid static feeding combined with Fe2+ addition as a novel strategy was employed to improve the formation and stability of AGS in treating low-strength wastewater. Fe-AGS was formed within only 7 days and showed favorable pollutant removal capability and settling performance. The ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD) concentration in the effluent were lower than 5 mg/L and 50 mg/L after day 23, respectively. The sludge volume index (SVI) and mixed liquid suspended solids (MLSS) was 37 mL/g and 2.15 g/L on day 50, respectively. Rapid static feeding can accelerate granules formation by promoting the growth of heterotrophic bacteria, but the granules are unstable due to filamentous bacteria overgrowth. Fe2+ addition can inhibit the growth of filamentous bacteria and promote the aggregation of functional bacteria (eg. Nitrosomonas, Nitrolancea, Paracoccus, Diaphorobacter) by enhancing the secretion of extracellular polymeric substances (EPS). This study provides a new way for AGS application in low-strength wastewater treatment.

Flexible UiO-67(Zr)@cyclodextrin-based nanofiber membrane for efficient removal of ibuprofen

The efficient removal of pharmaceutical pollutants in groundwater has become an urgent issue in sewage treatment. β-cyclodextrin (β-CD), a polysaccharide and rich in raw materials, has broad applications in adsorption and separation due to its host–guest interaction with many molecules. In this paper, a flexible and water-insoluble UiO-67(Zr)-modified cyclodextrin-based nanofiber membrane (UiO-67@β-CD-NP) was synthesized via a combination of electrospinning and solvothermal methods. By virtue of the synergetic adsorption effect of cyclodextrin and MOFs, the UiO-67@β-CD-NP shows excellent performance for ibuprofen (IBP) removal. The adsorption of IBP onto UiO-67@β-CD-NP was well-fitted with the pseudo-second-order kinetic model and Freundlich isothermal model, yielding an adsorption capacity of 226.24 mg/g. Furthermore, the UiO-67@β-CD-NP nanofibers demonstrate a high removal rate of 100 % and exhibit good regenerability in dynamic adsorption experiments. After the filtration of UiO-67@β-CD-NP, the chemical oxygen demand (COD) concentration of IBP has evidently reduced below the discharge standard of pharmaceutical sewage. This study provides a simple and novel strategy for preparing low-cost and high-performance composite nanofiber membrane incorporating cyclodextrin and MOFs. This membrane holds great potential as a candidate for adsorption applications in practical pharmaceutical sewage treatment.

The Effect of Compost Type, Application Rate, and Maturity on Nutrient Leaching and Soil Nutrient Levels

ABSTRACT The application of compost to agricultural soils can increase nutrient leaching, causing several environmental problems. Conversely, proper management of compost application can reduce environmental risks. Agronomical trials were conducted in greenhouses in Morocco to compare the effects of varying compost application rates, types, and maturity, as well as the number of growing days, on nutrient availability and nitrate leaching in a loamy sandy soil. Additionally, the study examined the impacts of these factors on soil physical and chemical characteristics. The compost used in this study was derived from a combination of two cost-effective materials, municipal waste, and poultry manure. Tomato plants were cultivated in pots amended with compost over a period of 65 days. The soils were treated with eight composts (plus a control) obtained from municipal solid waste (MSW) mixed with poultry manure (PM) at two ratios, 3:2 and 2:3 weight weight−1 (ww−1) (C1 and C2, respectively), used at two different ages (105 days and 173 days) and at two doses (32.5 g pot−1 and 65 g pot−1, equivalent to 40 Mg ha−1 and 80 Mg ha−1). Two simulated leaching events (the first after planting and the second at harvest) were performed. The concentration of chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) in leachate varied with the number of growing days and increased in the leachate of the non-amended soil after planting. At both sampling times, compost C1, aged 173 days (d), significantly decreased COD in the leachate compared to compost C1 aged 105 d. Compost increased nitrate leaching compared with the non-amended soil. Nitrogen leaching was primarily in the form of nitrate, ranging from 61% to 78% over the whole experimental period. Compost also decreased leachate concentrations of iron (Fe) and chromium (Cr), for other metals, such as cobalt (Co) and nickel (Ni), values were very low. Moreover, compost increased total organic carbon by up to twofold at both sampling times, with the most substantial increase observed with a dose of 65 g pot−1 of compost C2 (aged 105 days). Most compost treatments also increased available phosphorus (P), inorganic nitrogen (N), total nitrogen (TNK), cation exchange capacity (CEC), and electrical conductivity (EC) at both sampling times but had no effect on pH. The metal content in the soil exhibited a decrease compared to the control soil. Overall, our study suggests that nitrogen leaching can be reduced by optimizing compost rates, properties, and stability to synchronize with crop needs.

Research on the descaling characteristics of a new electrochemical water treatment device.

In recent years, chemical water treatment equipment has gained significant attention due to its environmental-friendly features, multifunctionality, and broad applicability. Recognizing the limitations of existing chemical treatment equipment, such as challenges in scale removal and the high water content in scale deposits, we propose a novel drum design for both anode and cathode, enabling simultaneous scale suction and dehydration. We constructed a small experimental platform to validate the equipment's performance based on our model. Notably, under the optimal operating parameters, the hardness removal rate for circulating water falls within the range of 19.6-24.46%. Moreover, the scale accumulation rate per unit area and unit time reaches 13.7 g h-1 m-2. Additionally, the energy consumption per unit weight of the scale remains impressively low at 0.16 kWh g-1. Furthermore, the chemical oxygen demand (COD) concentration decreased from an initial 106.0 mg L-1 to a mere 18.8 mg L-1, resulting in a remarkable total removal rate of 82.26%. In conclusion, our innovative electrochemical water treatment equipment demonstrates exceptional performance in scale removal, organic matter degradation, and water resource conservation, offering valuable insights for future research and development in chemical treatment equipment and electrochemical theory.

Approach enhancing nitrate removal from actual municipal wastewater by integrating electric-magnetic field with Fe0 in UMSR reactor

This study aimed to investigate the effectiveness of combining zero-valent iron (Fe0) with an electric-magnetic field (EMF) with an intensity of 48-mT generated by an alternating current (AC) of 6 V and 50 Hz applied deep within a reactor using actual wastewater obtained from a secondary stage of a wastewater treatment plant (WWTP). The lab-scale experiment was conducted using the UMSR reactor, maintaining a controlled temperature of 25 ± 2 °C and a hydraulic retention time (HRT) of 5-hour, with a dissolved oxygen (DO) level below 1.5 mg/L. Fine Fe0 particles with a size of ≤ 0.3 µm were added into the reactor at a concentration of 3 g/L. The actual wastewater had an approximate nitrate nitrogen (NO3–-N) concentration of 30 ± 2 mg/L, and the substrate mass ratio of carbon to nitrogen (C:N) was at 1:1. The results examined the performance of the EMF-Fe0 system in terms of nitrate removal efficiency and the enrichment of denitrifying bacteria, achieving a nitrate removal rate of 67 % with an effluent NO3–-N concentration of 10 mg/L and a chemical oxygen demand (COD) concentration of 11.8 mg/L at removal rate of 60 %. Illumina sequencing revealed various enriched denitrifying bacteria after coupling EMF with Fe0, including autotrophic Nitrospira (NOB) at 4 %, denitrification bacteria like Hydrogenophaga at 1.3 %, Hyphomicrobium at 1 %, and Sphingobium at 5 %, along with thermophilic bacteria Thermus at 1.1 % and Meiothermus at 3.5 %. PICRUSt predicted bacterial functions and analyzed interactions, while KEGG and GO analyses linked nitrogen removal pathways to specific species, genes, and enzymes in the EMF-Fe0 system.

Effects of land-use patterns on seasonal water quality at multiple spatial scales in the Jialing River, Chongqing, China

Land-use patterns usually impact river water quality as non-point pollution sources at both spatial and seasonal scales, which can provide important guidance for water pollution control and land-use planning after quantitative analysis. Here, surface water samples were collected from ten sampling points in the Chongqing Section of the Jialing River to monitor the physicochemical parameters of river water from March 2021 to February 2022. Our results showed significant seasonal changes in river water quality based on higher concentrations of dissolved oxygen (DO), ammonium nitrogen (NH 4+-N), and nitrate nitrogen (NO3–-N) in the wet season than those in the dry season, while the concentrations of chemical oxygen demand (CODcr) and total nitrogen (TN) in the dry season are higher than those in the wet season. Redundancy analysis (RDA) for elucidating the relationship between land-use patterns and river water quality parameters at multiple spatial (reach and riparian scale) and seasonal scales (dry and wet season) shows that water quality indices exhibited a strong positive correlation with construction land and farmland, inducing a negative impact on river water quality; while forest and grassland were inversely correlated to water quality indices, causing a positive effect on river water quality. On a seasonal scale, the land-use pattern showed more association with river water quality parameters in the wet season, compared to that in the dry season. The impact of the different buffer zones associated with land-use types on the river water quality was in the following order: 2000 > 500 ≈ 1000 m buffer. These findings contribute to sustainable land-use development and multi-scale landscape optimization to improve water quality in the Chongqing Section of the Jialing River.