Chemical Oxygen Demand Concentration Research Articles

Performance evaluation of species varied fixed bed biofilm reactor for wastewater treatment of Dhobi Khola outfall, Setopul, Kathmandu, Nepal

The sustainability of wastewater treatment plants poses significant challenges for developing countries, necessitating substantial investment for operation and maintenance. Biofilm reactors seeded with specific species of microorganisms were investigated under controlled environmental conditions. However, the performance evaluation of such reactors under natural conditions remains largely underexplored. This study investigated wastewater treatment capabilities of bench-scale fixed bed biofilm reactors, employing various species (Wastewater Microbes, Pseudomonas, Algae, and a co-culture of Algae and Pseudomonas). The reactors (Treatments and Control) were filled with 28 mm nominal-size local aggregates as packing media, operated under different contact times, and subjected to varying concentrations of heavy metals (Zn, Cd). To assess the reactor performances, the Bland-Altman Plot and Chemical Oxygen Demand (COD) removal kinetics were evaluated.The results revealed that the reactor initiated with a co-culture exhibited the optimal COD removal efficiency, reaching 84 ± 1 %. The reactor initially seeded with wastewater microbes exhibited the highest heavy metal elimination, achieving 94 ± 1 % and 88 ± 1 % removal for Zn and Cd respectively. The wastewater-seeded reactor demonstrated the zero-order COD removal kinetic coefficient (k) of 46.41 mg/L/h at an average influent COD concentration of 558 mg/L at 10 h contact time. While Pseudomonas-seeded reactor demonstrated k = 0.73 mg/L/h at 20 h contact time with 69 mg/L influent COD and heavy metal concentrations Zn = 26 mg/L and Cd = 3.57 mg/L.The findings of this study suggest that variations in environmental conditions, contact time, and heavy metal concentration have minimal impact on the pollutant removal efficacy of the reactors, and provide robust evidence for their viability as a sustainable alternative in municipal wastewater treatment. The study also identifies the possibility of treating specific wastewater characteristics by altering the dominant species in the reactors, paving the way for further research on the efficacy of other microbial genomes in fixed bed biofilm reactors.

Partial nitrification and simultaneous denitrification in sequential anaerobic and aerobic reactors: performance and microbial community dynamics

ABSTRACT The removal of organic matter and nitrogen from domestic sewage was evaluated using a system composed of two sequential reactors: an anaerobic reactor (ANR) with suspended sludge and an aerobic (AER) reactor with suspended and adhered sludge to polyurethane foams. Nitrogen removal consisted of AER operating at low dissolved oxygen (DO) concentrations; this favoured the simultaneous nitrification and denitrification (SND) process. The concentration of COD and N were 440 mgO2.L−1 and 37 mgTN.L−1, respectively. The operation was divided into three phases (P), lasting 51, 53, and 46 days, respectively. The initial DO concentrations applied in the AER were: 3.0 (PI) and 1.5 mg.L−1 (PII and PIII). In PIII, the AER effluent was recirculated to the ANR at a ratio of 0.25. Kinetic assays were performed to determine the nitrification and denitrification rates of the biomasses (ANR and AER in PIII). Changes in the microbial community were evaluated throughout phases PI to PIII by massive sequencing. In PIII, the best results obtained for chemical oxygen demand (COD) and total nitrogen (TN-N) removal efficiencies, were close to 94% and 65%, respectively. Under these conditions, system effluent concentrations below 30 mg COD.L−1 and 15 mg TN-N.L−1 were verified. The nitritation and nitration rates were 10.5 and 6.5 mg N.g VSS−1.h−1, while the denitrification via nitrite and nitrate were 6.8 and 5.8 mg N.g VSS−1.h−1, respectively. A mixotrophic community was prevalent, with Rhodococcus, Nitrosomonas, Pseudomnas, and Porphyromonas being dominant or co-dominant in most of the samples, confirming the SND process in the AER sludge.

Tertiary treatment of dairy wastewater applying a microalga-fungus consortium

ABSTRACT This paper aimed to apply filamentous fungi (Penicillium oxalicum and Cunninghamella echinulata), the microalga Tetradesmus obliquus and their co-culture in advanced treatment (tertiary treatment) of cheese whey. The bioremediation process was carried out in agitated flasks and bubble column bioreactors with different concentrations of chemical oxygen demand (COD) (223–1663 mg L − 1), total nitrogen (TN) (13–61 mg L − 1), and total phosphorus (TP) (3–26 mg L − 1). The results obtained in shaken flasks showed a superiority of the consortium compared to the systems with separated species. In this sense, the treatment was carried out in a bubble column reactor, and the consortium formed by the microalga and the fungus C. echinulata showed a greater efficiency (at a light intensity of 100 µmol m − 2 s − 1), promoting by the symbiosis to reach removal efficiencies of up to 93.7, 78.8 and 93.4% for COD, TN and TP, respectively; meeting Brazilian and European standards for discharge into water bodies. In addition, no pH adjustment was required during the co-culture treatment, demonstrating the buffering effect of using these two types of microorganisms. Therefore, the use of the consortium formed by T. obliquus and C. echinulata as a remediator was highly promising to promote the advanced treatment of cheese whey.

Introduction of Plug-flow Anaerobic Sludge Blanket (PASB) reactor for wastewater treatment

Plug-Flow Anaerobic Sludge Blanket Reactor (PASB) was used as the experimental reactor for the treatment as a replacement for Up-flow Anaerobic Sludge Blanket Reactor (UASB). The novelty of this study is to analyse the applicability of a novel post-treatment for anaerobically treated water by modifying UASB reactor which might be cost-effective, sustainable, and time-saving in the field of anaerobic treatment. Low-strength and high-strength (Leachate) wastewater (WW) were anaerobically treated under ambient temperature (28ºC-32ºC) with different Hydraulic Retention Time (HRT) values using a PASB and UASB setup. Chemical Oxygen Demand (COD) removal efficiency, biogas production rate, and gas composition were recorded and analysed. The average influent COD concentration of the low-strength wastewater was about 2070 ± 70 mg/L during the operation period of the reactor, and the COD removal efficiency of PASB was 90 ± 0.2 % which was 16 % enhancement at 10 h (hrs) HRT compared to UASB. The maximum biogas production recorded at this HRT was 13.72 ± 0.16 mL/h/L, which was 30.7 % higher than UASB. For leachate, COD concentration was about 6270 ± 220 mg/L, and COD removal efficiency was 97.2 ± 0.2 %. It is about a 23 % increase compared to UASB, at 8 hrs HRT and the maximum biogas production rate obtained for leachate treatment was 71.57 ± 1.53 mL/h/L and it was 30 % escalation than UASB. Hence, the PASB Reactor seems to be a desirable technique in compared with UASB to reach a comprehensive treatment efficiency, with efficient biogas exploitation to meet goals of renewable energy especially in tropical nations where less reactor heating is needed.

Assessment of biogas production potentials of palm oil mill effluent and cow dung substrates in anaerobic digester

The biogas production potentials of palm oil mill effluent (POME) and cow manure (CM) substrates were evaluated using anaerobic digester. The first two digesters (D1 and D2) were charged with POME and CM for mono-digestion respectively. However, co-substrates digestion was done in digesters D3 (60/40 % POME-CM), D4 (70/30 % POME-CM), and D5 (80/20 % POME-CM) and all the digestion lasted for 21 days. The biogas yield of the digesters and performance of the digestions were measured by the analysis of moisture content, pH, total suspended solids (TSS), total solids (TS), volatile solid (VS), chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total organic carbon (TOC) using standard analytical methods. The results showed that D4 (70/30 % POME-CM) has the highest biogas yield (1875±0.11 mL) while D2 (100 % CM) gave the lowest biogas yield (443±0.15 mL). The BOD of D3, D4 and D5 were not detected. The concentrations of COD, TS, TSS and TOC showed a significant (p<0.05) decrease in D1, D3, D4 and D5 compared to D2. While D2, D3, D4 and D5 showed a significant (p<0.05) decrease in moisture content compared to D1. However, D1, D3, D4 and D5 showed increasing level of alkalinity compared to acidic level of D2. Therefore, this study suggests that co-substrates anaerobic digestion of palm oil mill effluent and CM are suitable for biogas production.

Kinetics of Obtaining Microalgal Biomass and Removal of Organic Contaminants in Photobioreactors Operated with Microalgae—Study Case: Treatment of Wastewater from a Poultry Slaughterhouse

Increases in poultry industry production have resulted in the generation of more hazardous effluents with high nitrogen and chemical oxygen demand (COD) concentrations. It is necessary to develop more efficient technologies in terms of water purification without the need to increase the volumes of commonly used reactors. This work analyzed the addition of micronutrients (Mo, Zn, Cu, and Mn) for the cultivation of the microalgae Chlorella spp. and Spirulina maxima in poultry wastewater. The effects of micronutrients on the production of biomass and algal cells were also assessed. For the Chlorella species, removal efficiencies of up to 99.14% for COD and 99.33% for nitrogen were achieved; for the Spirulina strain, these efficiencies were 98% for COD and 99% for nitrogen. The modified Gompertz equation was used to analyze the kinetic parameters. For both microalgae, the R2 values were greater than 98%. The results indicated that the dose with the highest algal cell generation rate was dose 2 for Chlorella spp., at 4.35 days, and dose 1 for Spirulina maxima, at 6.26 days. Microalgae are biological alternatives suitable for wastewater treatment, and their pollutant removal efficiency can increase with the addition of micronutrients, which has additional benefits for the production of valuable biomasses for industrial applications.

Novel Ensemble Learning Approach for Predicting COD and TN: Model Development and Implementation

Wastewater treatment plants (WWTPs) generate useful data, but effectively utilizing these data remains a challenge. This study developed novel ensemble tree-based models to enhance real-time predictions of chemical oxygen demand (COD) and total nitrogen (TN) concentrations, which are difficult to monitor directly. The effectiveness of these models, particularly the Voting Regressor, was demonstrated by achieving excellent predictive performance even with the small, volatile, and interconnected datasets typical of WWTP scenarios. By utilizing real-time sensor data from the anaerobic–anoxic–oxic (A2O) process, the model successfully predicted COD concentrations with an R2 of 0.7722 and TN concentrations with an R2 of 0.9282. In addition, a novel approach was proposed to assess A2O process performance by analyzing the correlation between the predicted C/N ratio and the removal efficiencies of COD and TN. During a one and a half year monitoring period, the predicted C/N ratio accurately reflected changes in COD and TN removal efficiencies across the different A2O bioreactors. The results provide real-time COD and TN predictions and a method for assessing A2O process performance based on the C/N ratio, which can significantly aid in the operation and maintenance of biological wastewater treatment processes.

Electrochemistry promotion of Fe(Ⅲ)/Fe(Ⅱ) cycle for continuous activation of PAA for sludge disintegration: Performance and mechanism

In this study, electrochemistry was used to enhance the advanced oxidation of Fe(Ⅱ)/PAA (EC/Fe(Ⅱ)/PAA) to disintegrate waste activated sludge, and its performance and mechanism was compared with those of EC, PAA, EC/PAA and Fe(Ⅱ)/PAA. Results showed that the EC/Fe(Ⅱ)/PAA process effectively improved sludge disintegration and the concentrations of soluble chemical oxygen demand, polysaccharides and nucleic acids increased by 62.85%, 41.15% and 12.21%, respectively, compared to the Fe(Ⅱ)/PAA process. Mechanism analysis showed that the main active species produced in the EC/Fe(Ⅱ)/PAA process were •OH, R–O• and FeIVO2+. During the reaction process, sludge flocs were disrupted and particle size was reduced by the combined effects of active species oxidation, electrochemical oxidation and PAA oxidation. Furthermore, extracellular polymeric substances (EPS) was degraded, the conversion of TB-EPS to LB-EPS and S-EPS was promoted and the total protein and polysaccharide contents of EPS were increased. After sludge cells were disrupted, intracellular substances were released, causing an increase in nucleic acids, humic acids and fulvic acids in the supernatant, and resulting in sludge reduction. EC effectively accelerated the conversion of Fe(Ⅲ) to Fe(Ⅱ), which was conducive to the activation of PAA, while also enhancing the disintegration of EPS and sludge cells. This study provided an effective approach for the release of organic matter, offering significant benefits in sludge resource utilization.

Information extraction of UV-NIR spectral data in waste water based on Large Language Model

In recent years, with the rise of various machine learning methods, the Ultraviolet and Near Infrared (UV-NIR) spectral analysis has been impressive in the determination of intricate systems. However, the UV-NIR spectral analysis based on traditional machine learning requires independent training with tedious parameter tuning for different samples or tasks. As a result, training a high-quality model is often complicated and time-consuming. Large language model (LLM) is one of the cutting-edge achievements in deep learning, with the parameter size of the order of billion. LLM can extract abstract information from input and use it effectively. Even without any additional training, using only simple natural language prompts, LLM can accomplish tasks that have never been seen before in completely new domains. We look forward to utilizing this capability in spectral analysis to reduce the time-consuming and operational difficulties. In this study, we used UV-NIR spectral analysis to predict the concentration of Chemical Oxygen Demand (COD) in three different water samples, including a complex wastewater. By extracting the characteristic bands in the spectrum, we input them into LLM for concentration prediction. We compared the COD prediction results of different models on water samples and discussed the effects of different experiments setting on LLM. The results show that even with brief prompts, the prediction of LLM in wastewater achieved the best performance, with R2 and RMSE equal to 0.931 and 10.966, which exceed the best results of traditional models, where R2 and RMSE correspond to 0.920 and 11.854. This result indicates that LLM, with simpler operation and less time-consuming, has ability to approach or even surpass traditional machine learning models in UV-NIR spectral analysis. In conclusion, our study proposed a new method for the UV-NIR spectral analysis based on LLM and preliminary demonstrated the potential of LLM for application.

Potensi Pemanfaatan Enzim Biokatalitik dari Kulit Buah dan Sayur untuk Pengolahan Limbah Cair Rumah Sakit

Health services in hospitals produce hazardous and infectious waste that comes from sharing sources of activity. The research carried out experimentally in laboratory aims to determine the effect of biocatalytic enzyme treatment from fruit and vegetable peel (concentration variations of 5%, 10%, 15%) on pH, chemical oxygen demand (COD) levels, total suspended solids (TSS), and total coliforms of hospital liquid waste. From the research results, it was found that the addition of biocatalytic enzymes was very effective in reducing the total coliform concentration. The highest reduction in coliforms occurred with the addition of 15% enzyme, where there was a decrease from 1600 MPN/100 mL to 500 MPN/100 mL at a digestion time of less than 24 hours. After a digestion time of 2 days, no coliforms were found in the wastewater samples. However, there was a decrease in pH and an increase in TSS and COD concentrations which did not meet quality standards after being treated with enzymes at all concentration variations. The profile of changes in TSS and COD concentrations shows a decreasing trend with an increase in digestion time of 1 to 3 days, the values ​​obtained will still exceed the TSS and COD quality standards (30 mg/L and 100 mg/L). Meanwhile, the waste pH gradually increased with increasing digestion time up to 3 days at enzyme concentrations of 5% and 10%, namely 3.5 and 4.8. However, this value is still outside the permitted quality standard interval, namely 6-9.

Aluminum Waste as Electrode for Home Textile Industry Wastewater Treatment using Batch Electrocoagulation Process: Studies on Operating Parameters

The manufacture of the Sasirangan home textile industry involves coloring and dyeing processes using synthetic dyes in large quantities. These contaminants of dyes and organic materials would cause high color and chemical oxygen demand (COD) contaminants values. This study aims to characterize the wastewater of batik-modified Sasirangan and determine the effect of current density and length of operating time on color removal and reduction of COD in Sasirangan home textile industry wastewater through the batch electrocoagulation process. The method used in this research is an electric current flowing in the same direction to the Sasirangan home textile industry wastewater in a reactor with dimensions of 310 180 240 mm3. The electrode used is aluminum alloy type 1100. The aluminum/aluminum (Al/Al) electrode is used in this electrocoagulation (EC) process, then connected to a direct current (DC) power supply. The experiment was carried out at room temperature using an electrode distance of 2 cm with variations in the time of the electrocoagulation process for 15–120 minutes. The experiment was repeated for variations in pH (4–9) with a current density of 3.5–5.5 mA/cm2. Furthermore, an analysis of the color removal and the decrease in the concentration of COD was carried out. The results showed that the contaminant content in Sasirangan home textile industry wastewater decreased significantly, whereas the optimal conditions for the EC reaction were determined using color and COD removal efficiency parameters. The decrease in color and COD concentrations occurred at a current density of 5.5 mA/cm2 with a pH of 4 for 120 minutes, around 1110 PtCo and 90.4 mg/L of COD, respectively

Quality of Harvested Rainwater from a Green and a Bitumen Roof in an Air Polluted Region

A one-year study was conducted to evaluate the impact of air pollution and roof coating on runoff quality. An existing 440 sq meter bitumen roof of a single-story building was coated with an extensive green roof layer on one half. Rainfall and runoff samples from both roofs were collected during 11 rainfall events after the separation of the first flush. The study monitored several key parameters, including pH, electrical conductivity (EC), turbidity, chemical oxygen demand (COD), ammonium nitrogen, nitrate nitrogen, and phosphates. The study revealed that both types of roofs altered the rainfall quality, but the changes caused by the green roof were more substantial. Although the retention of runoff from green roofs has a widely acknowledged positive impact on collecting systems, our study shows that green roofs also result in a 7.5-fold increase in COD concentrations, a 5.4-fold increase in the sum of ammonium and nitrate nitrogen, and a 2.3-fold increase in phosphates compared to bitumen roofs. A clear link between the quality of rainwater/runoff and air pollution was not established. The study's findings will aid in the development and management of local rainwater harvesting systems and enhance global understanding of the primary quality parameters of various roof types, particularly in regions with air pollution. Doi: 10.28991/CEJ-2024-010-05-015 Full Text: PDF

Effect of pyrite particle size on the denitrification performance of autotrophic or split-mixotrophic bioreactors supported by pyrite/polycaprolactone.

In this study, a pyrite-based autotrophic denitrification (PAD) system, a polycaprolactone (PCL)-supported heterotrophic denitrification (PHD) system, and a pyrite+PCL-based split-mixotrophic denitrification (PPMD) system were constructed. The pyrite particle size was controlled in 1-3, 3-5, or 5-8mm in both the PAD and PPMD systems to investigate the effect of pyrite particle size on the denitrification performance of autotrophic or split-mixotrophic bioreactors. It was found that the PAD system achieved the best denitrification efficiency with an average removal rate of 98.98% in the treatment of 1- to 3-mm particle size, whereas it was only 19.24% in the treatment of 5- to 8-mm particle size. At different phases of the whole experiment, the nitrate removal rates of both the PHD and PPMD systems remained stable at a high level (>94%). Compared with the PAD or PHD system, the PPMD system reduced the concentrations of sulfate and chemical oxygen demand in the final effluent efficiently. The interconnection network diagram explained the intrinsic metabolic pathways of nitrogen, sulfur, and carbon in the three denitrification systems at different phases. In addition, the microbial community analysis showed that the PPMD system was beneficial for the enrichment of Firmicutes. Finally, the impact mechanism of pyrite particle size on the performance of the PPMD system was proposed. PRACTITIONER POINTS: The reduction of pyrite particle size was beneficial for improving the efficiency of the PAD process. The change in particle size had an effect on NO2 --N accumulation in the PAD system. The accumulation of NH4 +-N in the PPMD system increased with the decrease in particle size. The reduction of pyrite particle size increased the production of SO4 2- in the PAD and PPMD systems. The correlations among the effluent indicators of the PAD and PPMD systems could be well explained.

Multiomics study on co-fermentation of chemically enhanced sludge and waste activated sludge to produce volatile fatty acids under different temperatures and pHs

This study examined the effects of different temperatures (37°C and 45°C) and pH (uncontrolled, 8 and 10) on the co-fermentation of FeCl3, anionic polyacrylamide (a-PAM) settling chemical enhanced primary sedimentation (CEPS), and waste activated sludge (WAS) to produce volatile fatty acids (VFAs), which analyzed through characterization, microbial community, and untargeted metabolic pathways. Further, to investigate the interacting effects, temperatures of 37°C, 45°C, and pHs of 8 and 10 were chosen, with a sludge ratio of 7.5. The hydrolysis of sludge was aided by the concentration of soluble chemical oxygen demand (SCOD) rising as temperature and pH rose. Nevertheless, elevated SCOD concentrations failed to materialize into benefits for acid production. Therefore, considering practical applications, the optimal conditions for acid production were determined to be 37°C and pH 10, with a concentration of 3411.17 ± 119.92 mg COD/L. A thorough investigation of correlations between microbial communities, differential metabolites, and environmental factors was carried out, highlighting the significance of pH in relation to microbial and acid production performance. That instance, the pH affects acid generation efficiency more so than temperature parameters. Within the microbial community, there is a considerable positive correlation between several distinct metabolites and Steptococcus, Trichococcus, and Tepidimimicrobium. These metabolites are intimately associated with the materials and energy needed for biological cell production and metabolism. This could be as a result of how environmental influences alter the distribution of microbial populations, which influences various metabolites and ultimately the process of producing acid.

Evaluation of the Performance of Wastewater Treatment Plant at Steel Mill Karachi, Pakistan

The purpose of this study is to evaluate how well Steel Mill Karachi's wastewater treatment system works. Wastewater treatment facilities employ the activated sludge technique. Several influent and effluent locations allowed for the collection of influent and effluent samples. A number of physicochemical parameters, such as total dissolved solids (TDS), biochemical oxygen demand (BOD5), total suspended solids (TSS), chemical oxygen demand (COD), electric conductivity (EC), pH, and other metals, such as potassium (K), iron (Fe), sulphate (SO4-2), calcium (Ca), sodium (Na), zinc (Zn), and magnesium (Mg), were measured in order to evaluate the effectiveness of wastewater treatment plants. In a lab environment, the sample's analysis findings were compared to Sindh Environmental Quality Standards (SEQS) for Pakistan. EC, BOD5, COD, SO4-2, Ca, Mg, Na, K, TDS, TSS, EC, BOD5, COD, SO4-2, Ca, Mg, Na, K, Fe, and Zn were removed to different degrees: 42.93%, 60.33%, 43.63%, 51.53%, 40.5%, 35.56%, 26.33%, 22.12%, 34.09%, 20.75%, 55.87%, 22.12%, and 76.10%. Only two metrics, the COD and Zn concentrations, were over the SEQS limits, keeping other effluent results parameters within the limits. Additionally, it is advised that proper maintenance be carried out to increase the effectiveness of wastewater treatment plants.

Pipeline Terracotta Microbial Fuel Cell: Organic Content Biosensor and Energy Harvesting Device Integrated in Wastewater Pipeline.

Wastewater pipelines are present everywhere in urban areas. Wastewater is a preferable fuel for renewable electricity generation from microbial fuel cells. Here, we created an integrated microbial fuel cell pipeline (MFCP) that could be connected to wastewater pipelines and work as an organic content biosensor and energy harvesting device at domestic waste-treatment plants. The MFCP used a pipeline-like terracotta-based membrane, which provided structural support for the MFCP. In addition, the anode and cathode were attached to the inside and outside of the terracotta membrane, respectively. Co-MnO2 was used as a catalyst to improve the performance of the MFCP cathode. The experimental data showed a good linear relationship between wastewater chemical oxygen demand (COD) concentration and the MFCP output voltage in a COD range of 200-1900 mg/L. This result implies the potential of using the MFCP as a sensor to detect the organic content of the wastewater inside the wastewater pipeline. Furthermore, the MFCP can be used as a long-lasting sustainable energy harvester with a maximum power density of 400 mW/m2 harvested from 1900 mg/L COD wastewater at 25 °C.

A Study of the System Performance and the Microbial Community Composition of Chemical Wastewater in an AO-MBBR Treatment Process

To improve the nitrogen removal and reduce the chemical oxygen demand (COD) of a full-scale wastewater treatment plant, two sequential batch reactor devices were used to treat chemical wastewater with biocarriers in low carbon-to-nitrogen (C/N) ratio conditions. The results showed that the addition of biocarriers to the anoxic tank reduced the average concentration of COD in the effluent from 98.1 mg/L to 80.7 mg/L and increased total nitrogen (TN) removal by 9.4%. Metagenomic sequencing was performed to study the composition and function of microbial community samples taken from anoxic sludge and anoxic-carrier biofilms in this wastewater treatment plant. The results showed that Proteobacteria and Actinobacteria were the dominant phyla in the two samples, ensuring their capability for organic matter removal. The anoxic-carrier biofilms were mainly enriched with denitrifying bacteria such as Thauera (10.7%) and Comammonas (2.2%) and the anammox bacteria Candidatus Kuenenia (0.03%). Meanwhile, the nitrogen metabolism pathway was elaborated and the abundance of the functional genes involved in the nitrogen metabolism pathway was quantified. In addition, results from qPCR showed increased copy numbers of denitrification and anammox genes in the anoxic-carrier biofilms compared to those in the anoxic sludge, further confirming the enrichment of functional bacteria.

Enhancing pollutant removal efficiency in urban domestic wastewater treatment through the hybrid multi-soil-layering (MSL) system: A case study in Morocco.

This paper evaluates the performance and potential of a full-scale hybrid multi-soil-layering (MSL) system for the treatment of domestic wastewater for landscape irrigation reuse. The system integrates a solar septic tank and sequential vertical flow MSL and horizontal flow MSL components with alternating layers of gravel and soil-based material. It operates at a hydraulic loading rate of 250 L/m2/day. Results show significant removal of pollutants and pathogens, including total suspended solids (TSS) (97%), chemical oxygen demand (COD) (88.57%), total phosphorus (TP) (79.93%), and total nitrogen (TN) (88.49%), along with significant reductions in fecal bacteria indicators (4.21 log for fecal coliforms and 3.90 log for fecal streptococci) and the pathogen Staphylococcus sp. (2.43 log). The principal component analysis confirms the effectiveness of the system in reducing the concentrations of NH4, COD, TP, PO4, fecal coliforms, fecal streptococci, and fecal staphylococci, thus supporting the reliability of the study. This work highlights the promising potential of the hybrid MSL technology for the treatment of domestic wastewater, especially in arid regions such as North Africa and the Middle East, to support efforts to protect the environment and facilitate the reuse of wastewater for landscape irrigation and agriculture.

Cultivation of Microalgae in Liquid Digestate to Remove Nutrients and Organic Contaminants

The goal of this research was to assess the efficiency of the liquid digestate treatment conducted with algal, environmental isolates illuminated entirely with sunlight. The photobioreactor was exposed to natural conditions and evaluated based on the reduction of chemical oxygen demand (COD), nitrogen compounds, and soluble phosphates. Microalgal and bacterial communities growing during the treatment process were studied. A high removal rate of soluble COD (= 91%) and nutrients (= 86%) was achieved. The average concentrations of nitrogen, phosphates, and COD in the reactor effluent were 95 mgN/L, 49 mg/L, and 735 mg O2/L, respectively. The overall algae-bacteria biomass productivity of 22 mg/L/d, calculated on the total suspended solids (TSS) basis, was recorded. The microbial analysis revealed the dominance of Tetradesmus obliquus followed by Microglena sp. in the first 14 weeks of the experiment. At the end of the experimental run, Chlorella sorokiniana cells appeared as a result of illumination intensity changes. The dominating bacteria belonged to Firmicutes (26.31%), Patescibacteria (17.38%), and Actinobacteriota (14.86%) and could have been responsible for the transformation of nitrogen and oxidation of organic contaminants. The research demonstrated that natural sunlight can successfully be used for efficient liquid digestate treatment with the algae-bacterial community.

Is water replenishment an effective way to improve lake water quality? Case study in Lake Ulansuhai, China

Lakes are an important component of the global water cycle and aquatic ecosystem. Lake water quality improvement have always been a hot topic of concern both domestically and internationally. Noncompliant outflow water quality frequently occurs, especially for lakes that rely mainly on irrigation return flow as their water source. External water replenishment to improve the water quality of lakes is gradually being recognized as a promising method, which however, is also a controversial method. Lake managers, in the case of constant controversy, hesitate about the appropriateness of lake water replenishing. Thus, taking Lake Ulansuhai in China as an example, this study aimed to construct a lake hydrodynamic and water quality model, under the constraint of multiple boundary conditions, that has sufficient simulation accuracy, and to simulate and analyze the changes in COD (Chemical Oxygen Demand) and TN (Total Nitrogen) concentrations in the lake area before and after water replenishment, and explore whether water replenishment was an effective method for improving lake water quality. The results showed that when the roughness value of Lake Ulansuhai was 0.02, the TN degradation coefficient K was 0.005/d, and the COD degradation coefficient K was 0.01/d; the simulation and measured values had the best fit, and the built model is reasonable and reliable can be used to simulate lake water quality changes. By external water replenishment lasting 140 days in the water volume of 4.925 × 108 m³, the COD and TN concentrations in Lake Ulansuhai could be stabilized at the Class V water quality requirement, which helped improve the self-purification ability of the lake area. Water replenishment was proved to be an effective method for improving the water quality of the lake, but water replenishment is only an emergency measure. Lake water replenishment is more applicable to areas with abundant water resources. External source control and internal source reduction of lake pollution and protection of lake water ecology are the main ways to improve lake water quality for water-deficient areas under the rigid constraints of water resources. In the future, key technologies for reducing and controlling pollution in irrigation areas, construction of lake digital twin platforms, and active promotion of lake legislation work should be the main research direction for managing the lake water environment.