Total Kjeldahl Nitrogen Research Articles

The potential of alkaline tolerant microbial consortia for textile wastewater treatment under integrated anaerobic/aerobic conditions: Performance evaluation and microbial community analysis

Sequential anaerobic/aerobic (A/O) treatment conditions for textile wastewater (WW) are more effective than conventional biological treatment. Anaerobic treatment is essential because anaerobic microbes can first break down complex and recalcitrant compounds, which are difficult to degrade under aerobic conditions. The simpler, more degradable compounds are then further broken down by aerobic microbes. This study aimed to evaluate the performance of a sequential A/O treatment process using a pilot-scale reactor to treat real textile WW and to characterize reactor and inoculum microbial community structures. The reactors were inoculated with microbial consortia originating from a diverse alkaliphilic soda lake in the Ethiopian Rift Valley. The WW test parameters were used to evaluate the performance of the treatment process. At steady state, the removal efficiencies were 97 % for dye, 86 % for Chemical Oxygen Demand (COD), and 93 % for Total Kjeldahl Nitrogen (TKN). Amplicon sequencing revealed that Firmicutes, Proteobacteria, and Actinobacteria were the dominant phyla in all the samples. Uncategorized microorganisms, followed by Alkalibacterium, Bifidobacterium, and Clostridium were the most abundant taxon in all the samples. The microbial community detected during the treatment process was not abundant in the inoculum originating from Lake Chitu, suggesting that the communities likely originated from textile WW. The textile WW treated with the integrated A/O process effectively degraded dyes, and the inoculated microbes demonstrated resistance to the toxic chemical composition of the WW. The integrated treatment process, along with the alkaliphilic microbial consortia, has proven to be practical for treating textile WW, offering valuable insights for field-scale applications.

In-Vessel Aerobic Composting of Organic Waste Using Synthetic and Natural Bulking Agents

The escalating growth in municipal solid waste production underscores the imperative need for efficient waste management, especially given that a substantial portion of MSW comprises biodegradable materials suitable for composting. This study investigates the impacts of using a synthetic bulking agent (perforated plastic balls) in conjunction with biochar, a natural bulking agent, on the aerobic composting of kitchen waste. The study aim to evaluate the effectiveness of this combined approach in optimizing the composting process. Four trials, each spanning 30 days, were conducted to assess the effects of different combinations of synthetic and natural bulking agents. The study uses a uniform-size perforated synthetic bulking agent in combination with biochar to enhance the composting process. Results indicate that incorporating the perforated plastic balls (8% by weight) alongside biochar significantly influenced key composting parameters. This approach accelerated the initial rise in temperature to 55°C, enhanced the reduction of total organic carbon, improved total Kjeldahl nitrogen retention, and facilitated the achievement of optimal carbon-nitrogen (C/N) ratios ranging from 19 to 20. Furthermore, the analysis of phosphorus (P) and potassium (K) loss during composting revealed that potassium is more susceptible to leaching than phosphorus due to its higher mobility. The study concludes that the addition of a uniform-size perforated synthetic bulking agent, constituting 8% (by weight), in conjunction with a natural bulking agent, effectively enhances the composting process.

Impact of Landfill Leachate on Groundwater Quality and Health Risk Assessment in Mohammedia Prefecture, Morocco

Several studies have been conducted to identify the potential impact of landfills on groundwater resources. This study evaluates the impact of landfills on groundwater resources in Mohammedia prefecture, Morocco. The groundwater was analysed from 2015 to 2022. The groundwater quality was evaluated based on electrical conductivity, pH, biological oxygen demand, chemical oxygen demand, total Kjeldahl nitrogen, phosphate, suspended solids, dissolved oxygen, ammonia, and total hydrocarbon, aluminium, iron, cadmium, chromium, copper, iron-nickel, zing, and mercury. The assessment was based on the water quality index, leachate pollution index, non-carcinogenic risk assessment, and carcinogenic risk assessment. A leachate pollution index <5 indicates that it poses a severe risk to groundwater resources. The non-carcinogenic risk HQ was determined to be <1, which infers no potential risk. The carcinogenic risk index value of 10-4 indicated that it is within the threshold of acceptable limit. The current study concludes that leachate from the analysed landfills does not infiltrate the groundwater resources of Mohammedia prefecture. However, the leachate pollution, even though it varies, is increasing over time. This is validated by the fact that the landfill is protected with a membrane covering the ground, which inhibits any possible infiltration of soil or water resources. Hence, this study calls for continuous monitoring of groundwater resources in the region. Future studies are required to investigate the groundwater in Mohammedia prefecture in terms of emerging pollutants to identify any potential risk.

Influence of Organic Loading Rates on the Treatment Performance of Membrane Bioreactors Treating Saline Industrial Wastewater

This study investigated the efficacy of membrane bioreactor (MBR) technology in treating saline industrial wastewater, focusing on the impact of the organic loading rate (OLR) and the food-to-microorganism (F/M) ratio on treatment performance. This research utilized saline industrial wastewater from Al-Hasa, which had salinity levels ranging from 5000 to 6900 mg/L. It explored treatment processes at varying Chemical Oxygen Demand (COD) concentrations of 800, 1400, and 2000 mg/L, corresponding to an OLR of 0.80 ± 0.05, 1.41 ± 0.07, and 1.98 ± 0.12 g COD/L, respectively. The average F/M ratios used were 0.20, 0.36, and 0.50 g COD/g MLSS·d, maintaining a constant Sludge Residence Time (SRT) of 12 days, a hydraulic retention time (HRT) of 24 h (hrs.), and a flux of 10 L/m2·h. The MBR system demonstrated high COD removal efficiencies, averaging 95.7 ± 1.6%, 95.5 ± 0.4%, and 96.1 ± 0.3%, alongside Biochemical Oxygen Demand (BOD) removal rates of 98.3 ± 0.2%, 99.8 ± 0.1%, and 98.5 ± 0.1%, respectively. However, an increased OLR led to elevated residual COD and BOD levels in the treated effluent, with COD concentrations reaching 34.2 ± 12.8, 63.3 ± 5.9, and 76.5 ± 5.4 mg/L, respectively. This study also reveals a significant decline in ammonia and Total Kjeldahl Nitrogen (TKN) removal efficiencies as OLR increases, dropping from 96.1 ± 0.5% to 80.2 ± 0.9% for ammonia and from 83.8 ± 3.4% to 65.8 ± 2.3% for TKN. Furthermore, higher OLRs significantly contribute to membrane fouling and elevate the transmembrane pressure (TMP), indicating a direct correlation between OLRs and operational challenges in MBR systems. The findings suggest that for optimal performance within the Saudi disposal limits for industrial wastewater, the MBR system should operate at an F/M ratio of ≤0.33 g COD/g of Mixed Liquor Suspended Solid (MLSS)·d. This study underscores the critical role of the OLR and F/M ratio in treating saline industrial wastewater using MBR technology, providing valuable insights for enhancing treatment efficiency and compliance with environmental standards.

A hybrid BOA-SVR approach for predicting aerobic organic and nitrogen removal in a gas-liquid-solid circulating fluidized bed bioreactor

This study introduces the hybrid of the Bayesian optimization algorithm and support vector regression (BOA-SVR) models to predict the removal of aerobic organic (total chemical oxygen demand, COD) and nitrogen compounds such as total Kjeldahl Nitrogen (TKN), ammonium nitrogen (NH4-N), and nitrate nitrogen (NO3-N) from municipal wastewater in a gas-liquid-solid circulating fluidized bed (GLSCFB) bioreactor. GLSCFB bioreactors treat wastewater by removing nutrients biologically. The downer of a GLSCFB bioreactor provided experimental data on TKN, NH4-N, NO3-N, and TCOD removal. The hybrid optimal intelligence algorithm (BOA-SVR) has improved model accuracy across multiple domains by combining BOA and SVR. The coefficient of determination (R2), residual, mean absolute error (MAE), root mean square error (RMSE), and fractional bias (FB) were used to analyze BOA-SVR model performance. The models match experimental data from four operational stages well, with R2 or adj R2 values above 0.99 for all responses. The model's accuracy was confirmed by relative deviations and residual plots showing dispersion around the zero-reference line. The BOA-SVR model consistently predicted dependent variables with low RMSE and MAE values (≤ 2.24 and 2.21, respectively) and near-zero FB. Computing efficiency was shown by optimizing TCOD, TKN, NH4-N, and NO3-N models in 70.61, 72.89, 74.37, and 54.07 s. A rigorous test on unseen data with different noise levels confirmed the model's stability. Furthermore, BOA-SVR performs better than traditional multiple linear regression (MLR). Overall, the BOA-SVR model predicts biological nutrient removal in municipal wastewater utilizing a GLSCFB bioreactor quickly, correctly, and efficiently, reducing experimental stress and resource use.

Insight into the differential response of functional denitrifiers to novel formulated organic amendments in soybean agroecosystem

Fertilizer application has been known to cause substantial changes in the microbial composition of agricultural soil. Therefore, there is a need for more fertilizer management practices that will improve nitrogen (N) content, which is the key restrictive factor for microbial growth. To elucidate the characteristics of these fertilizers in the soil, samples were collected from a soybean field of control (S0) with no addition of organic amendment, biochar made from rice straw (S1), compost made from cattle manure and maize straw at a ratio of 5:1 (S2), composting S2 + 10 % S1 (S3), and mixture of S2 + 10 % S1 without composting (S4). The soil functional denitrifiers (nirS and nirK) were unravelled using Illumina high-throughput sequencing. It was observed that S3 (66.56 %) and S4 (61.14 %) increased the NO3−-N, while S2 increased the total Kjeldahl nitrogen (TKN) by 15.79 % compared to S0. OTU847_norank_p_environmental_samples in nirS and OTU112_unclassified_f_Bradyrhizobiaceae in nirK were the most abundant genera in S1-S4 while S2 and S3 had the highest unique OTUs in nirK and nirS communities, respectively. The canonical correspondence analysis (CCA) showed that NO2−-N and nitrate reductase (NIR) enzyme-shaped nirS and nirK denitrifiers. Also, from the structural equation model (SEM), TKN showed a higher negative significant effect on nirK alpha and beta diversities, while S4 showed the lowest positive network in nirS and nirK- denitrifiers. Meanwhile, Bradyrhizobium was observed as a common genus in the multivariate co-occurrence network in nirS- and nirK-type denitrifiers. This study provides the theoretical basis and technical support that single and combined fertilizers could influence nirS and nirK denitrifiers in soybean-grown soil.

Impact of lowering nitrogen content in pig manure through low crude protein diets on anaerobic digestion process stability, biogas yields, and digestate composition

Lowering crude protein in pig diets can reduce nitrogen (N) excretion and alter manure characteristics. Anaerobic digestion (AD) offers potential for converting pig manure into biogas and bio-based fertilizers (i.e., digestate). However, limited research exists on the effects of N content in pig manure on AD when pigs are fed diets with varying crude protein levels. This study investigated how lowering N content in pig manure through low crude protein diets may affect AD process stability, biogas generation, and digestate properties. Manures from different dietary treatments, named as control (CON), low N (LN), and very low N (VLN), with Total Kjeldahl Nitrogen concentrations of 5.87, 5.42, and 5.15 g/L, respectively, were investigated. Daily biogas production, composition (CH4, CO2, and H2S), and digestate properties were monitored over 13 fed-batch cycles (25 ± 4 days per cycle). The experiment was conducted at 20 ± 1 °C, a condition suited for milder climate regions, using six single-stage digesters operated in sequencing fed-batch mode. Data were analyzed by ANOVA using PROC MIXED with repeated measures. Results showed that the differences in N content in pig manure due to the three dietary treatments had a limited impact on biogas generation, with specific methane yields remaining similar over time. CH4 concentrations remained stable between 60 and 65 %, ensuring high-quality biogas despite dietary variations. Differences between treatments became more pronounced with increased organic loading rates (OLRs) due to variations in the amount of volatile solids fed. AD also remained stable (Total Volatile Fatty Acids/Total Alkalinity <0.25) even at an OLR of 2.15 g of chemical oxygen demand L−1 day−1, highlighting AD's robustness at lower temperatures. Digestate samples contained essential minerals beneficial for plant growth. More research is needed to explore varied manure compositions and feeding strategies to better understand the interactions of animal nutrition with AD.

Optimizing vertical farm cultivation of Cichorium spinosum L.: White Light's influence and nutrition management

The objective of this study was to examine the integration of a wild leafy vegetable, Cichorium spinosum L., in vertical farms. This research comprises two experiments focusing on different “white” light products and nutrient solutions. During both experiments, the temperature varied between 25 and 28 °C, relative humidity ranged from 50 to 70 %, carbon dioxide was at 450 ppm, and light intensity was set at 300 μmol m−2 s−1 respectively. In the lighting experiment, the three spectra used had the commercial names Neutral, Full and a SunLike™, and their spectral composition (blue:green:red:far-red) were 14:32:43:10, 16:36:40:8, and 21:34:36:7 respectively. The photoperiod was set to 12 h and the plant density was 50 plants m−2. Results showed no significant impact on agronomical parameters and leaf anatomy. The stomatal length and width decreased as the red:blue ratio of the light sources decreased, being greater in the Neutral treatment (red:blue ratio of 3.1) compared to the Full and SunLike™ (red:blue ratios of 2.5 and 1.7 respectively). Based on these results the preferable “white light” product was the one with the highest efficiency and lowest market price at the time of the experiment. In the nutrient solution experiment, the agronomical and nutritional attributes of stamnagathi plants supplied with a control nutrient solution, “N10-Fe15” were compared to plants cultivated under limited nitrogen, “N4-Fe15” and elevated iron, “N10-Fe48”, EC was 1.5 ds m−1, and pH was 5.6–6.5. The experiment simulated commercial practices by increasing the photoperiod to 15 h and plant density to 100 plants per square meter. The results did not demonstrate significant effect of the nutrient solution differences on the agronomical characteristics except from a decrease in total Kjeldahl nitrogen under limited nitrogen conditions. Notably, leaf tissue phosphorus content increased under elevated iron conditions. The nitrate content remained within safe for consumption thresholds for all treatments. Based on these results, stamnagathi can be integrated in vertical farms under limited nitrogen conditions. Stamnagathi's resilience to elevated iron in the nutrient solution demonstrated its potential for future biofortification experiments.

Biochar as ammonia exchange biofilm carrier for enhanced aerobic nitrification in activated sludge

The effects of biochar on aerobic nitrification in activated sludge were investigated in sequencing batch reactors. Biochar amended reactors exhibited 87–94 % lower ammonia in effluent and 16–71 % greater removal of total Kjeldahl nitrogen compared to control reactors. Quantitative qPCR analyses revealed that the relative abundance of ammonia oxidizing bacteria (AOB, amoA/16S rRNA genes) was greater in biochar than in control reactors. AOB were enriched on biochar surfaces, with biochar particles having up to 12.1 times greater relative abundance of AOB compared to suspended biomass. Biochar’s maximum ammonia sorption capacity of 4.4 mg N/g at pH 7 decreased with decreasing pH, however a pH-sensitive fluorescent probe was used to show that biofilms growing on biochar surfaces maintain a median pH of > 6.7 despite reactor acidification by nitrification. Microbial colonization of biochar in activated sludge creates a pH-sheltered environment that sustains biochar’s ammonia sorption capacity, resulting in enrichment of AOB on biochar particles and improved nitrification.

Evaluation of substrates for optimizing vermicomposting products

The high global market value of fresh mushrooms implies high importance of spent mushroom substrate (SMS) as a by-product that poses environmental challenges, if not properly treated. Reported studies demonstrate the positive effects of SMS on earthworm growth and reproduction, particularly when combined with other substrates such as cow dung (CD). This study utilized SMS and CD as substrates in varying ratios. A total of 375 young non-clitellated Eisenia fetida were randomly assigned to plastic containers, ensuring similar average individual worm weight, and maintained at 50% to 60% moisture. Weekly observations were made on earthworm average weight, cocoon production, and hatchling count. The growth and reproduction of earthworms differed significantly among treatments, with Treatment 3 (T3) (50:50 SMS and CD) showing the highest growth and Treatment 5 (T5) (0:100 SMS and CD) the lowest. Changes in pH, EC, total Kjeldahl nitrogen (TKN), total organic carbon (TOC), C/N ratio, and total available phosphorus (TAP) were observed over the experimental period, indicating dynamic nutrient dynamics within the substrates. The exchangeable potassium decreased with increasing proportions of CD, while the exchangeable sodium content showed variation across treatments. The observed variations can be attributed to differences in initial substrate composition and microbial activity during vermicomposting.

Reduction of organic matter containing benzimidazole and toxicity in real livestock wastewater through advanced oxidation processes

Livestock wastewater (LWW) has a complex characteristic of high organic matter content, metals, nutrients, and pharmaceutical compounds. Advanced oxidation processes (AOP) are a potential option for treating this wastewater. This study evaluated real LWW and the performance of UV/H2O2 and UV/peroxymonosulfate (UV/PMS) for its treatment. The experiments were conducted in a UV photoreactor (16 mW/m2, λ = 254 nm). The oxidant agents (Ox) tested were H2O2 and PMS, each at low, medium, and high TOC/Ox molar ratios. A pretreatment based on chemical precipitation was implemented. Annually, the LWW showed total organic carbon (TOC) values of 859 ± 13.37 mg/L, 168.85 ± 1.62 mg/L of total Kjeldahl nitrogen (TKN), and toxicity of 96% v/v. In the dry season, albendazole (ABZ) (95.3 ± 35.16 mg/L), Cu (4.3 ± 0.23 mg/L), Fe (3.8 ± 0.38 mg/L), and suspended solids (SS) (1015 ± 586.9 mg/L) were identified, so pretreatment was implemented. The UV/PMS process with the lowest molar ratio [TOC/Ox 1:0.75] removed significantly lower TOC concentrations (p < 0.05), but toxicity decreased entirely. The study of mineralization and toxicity provided insight into the changes in LWW during treatment with AOP. Furthermore, it contributed to establishing the technical basis for implementing efficient treatment processes.

CONSTRUCTED WETLANDS FOR NITROGEN REMOVAL AND SIMULTANEOUS REUSE OF DOMESTIC SEWAGE

This study evaluated the behavior of vertical flow constructed wetland (VFCW), planted with irrigated rice (Oryza sativa L.), specie BRS-GO Guará, and a vertical flow soil filter without plant (VFSF-CTR), as control, both on a reduced experimental scale. The objective was the removal and recovery of N from domestic sewage, using soil latossoil red-yellow (LRY) mixed with medium sand (modified LRY) as support medium. The operation of VFCW and VFSF-CTR for ten months and two rice crop cycles, used three different hydraulic loading rates - HLR (4.0, 8.0 and 15.0 cm/d); with three repetitions, totalizing eighteen experimental units. For the VFCW, the total Kjeldahl nitrogen (KTN) and N-NH4+ removal efficiencies, ranged from 86% to 95%; and, for VFSF-CTR, from 79 to 94%; with the rice crop favoring higher efficiencies in KTN removal, independent of HLR. Both systems showed tertiary treatment removal efficiency in a single stage; in addition, the variations in the removal efficiencies were minimal when operated with HLR of 15 cm/d. There was great accumulation of KTN and mineral N (N-NH4+ and N-NO3-) in soil, mainly in the 0-5 cm soil layer, which can be used for fertilization of other crops. There was also N immobilised in microbial biomass (MBN). This rapid fertilisation improved the soil quality in a short term (ten months of sewage application) and provided the production of grains and vegetable biomass for human and animal food. The VFCW presented good results, either operated with low or high hydraulic loads, showing larger operational flexibility.

Application of municipal solid waste (MSW) char during rotary drum co-composting (RDC) of vegetable waste and its characterization.

Composting, a sustainable method for handling biodegradable waste constituting nearly 50% of municipal solid waste (MSW), can be enhanced by incorporating char produced from MSW pyrolysis. This study investigates the impact of MSW char (0% char-Control, 2.5% char-Trial 1, 5% char-Trial 2) on the physicochemical properties of vegetable waste compost. A thermophilic temperature range of 53.8°C was detected in Trial 2, 50.8°C in Trial 1, and 46.8°C in Control. The pH of the mixes increased at day 20 to 7.5, 7.87, and 8.2 in Control, Trial 1, and Trial 2, respectively. The highest drop of total organic carbon (TOC) and volatile solids in Trial 2 is about 21.18% and 21.02%, respectively. Total Kjeldahl nitrogen (TKN) increased, particularly in Trial 2 (2.35%), while NH4-N concentrations decreased, and phosphorus levels rose notably to 23.48mg/kg, with 2.49mg/kg available phosphorus in Trial 2. The C/N was reduced to 10 in Trial 2. Total potassium increase was highest for Trial 1 (6.9g/kg). Trial 2 had the highest overall macronutrient concentration and correspondingly showed the greatest decrease in volatile solids. Furthermore, Trial 1 demonstrated a reduction in heavy metal concentration in comparison to Control and Trial 2. Consequently, the utilization of MSW char during rotary drum composting enhances the process of composting and significantly improves compost quality, making it a sustainable waste management solution.

Performances of full-scale biological nitrogen pre-treatment process for drinking water source: Seasonal variations and microbial community

This study investigated the performance of the full-scale unit over a two-year period to enhance nitrification efficiency and provide operational strategies. Results indicated that raw water quality from Donggan River was notably influenced by seasonal variations, particularly during dry and wet seasons, impacting the nitrification efficiency of the biological pretreatment process. Factors such as influent concentrations of ammonia and total Kjeldahl nitrogen were found to have significant effects on nitrification, with temperature and conductivity also showing correlations. The specific rate of ammonia removal was calculated to be approximately 0.1 kg-N/m3/d under the existing operational setup. Moreover, elevating dissolved oxygen levels above 4 mg/L was proposed to potentially boost ammonia oxidation based on findings from experiments conducted in lab-scale bioreactors. In times of increased influent ammonia levels, the elimination of about 1–3 mg-N/L of total nitrogen signified the activation of denitrification processes. This observation was corroborated by results from next-generation sequencing techniques, verifying the existence of denitrifying microorganisms. The real-time PCR analysis results indicated that the abundance of comammox amoA gene was comparable with the abundance of the AOB amoA gene, indicating the presence of comammox Nitrospira and their potential role on nitrification in the system.

Field study on the integration of a hydrogen-producing microbiome in restoring Phellinus noxius-affected rhizosphere

At National Kaohsiung University of Science and Technology (NKUST), a mesophilic anaerobic bioreactor system produces a hydrogen-producing microbiome (HMb) containing beneficial bacteria such as Bacillus sp. This HMb, known for degrading cellulose and remediating soil, is being tested in Kaohsiung City, Taiwan, to treat tree root rot caused by Phellinus noxius (P. noxius). The study aims to evaluate HMb's effectiveness in restoring the rhizosphere, enhancing soil health, and increasing tree resistance by assessing soil bioactivity and microbial diversity.Field experiments showed that HMb treatment improved tree health by 24 % at the highest health level but reduced it by 20 % at the next level. Post-treatment soil organic matter (SOM) and total Kjeldahl nitrogen (TKN) levels remained stable, indicating minimal impact on soil fertility. HMb also lowered soil pH in some plots, potentially suppressing pathogens and enhancing nutrient absorption. The study found that HMb increased microbial diversity in the rhizosphere, particularly Acidobacteria and Proteobacteria, which inhibited fungal growth. However, HMb had no significant impact on P. noxius populations. Overall, HMb treatment shows promise in enhancing plant health by improving microbial diversity and soil conditions, but further research is needed to understand its full impact on pathogen suppression and soil health restoration.

Evaluation of the potential ultrafiltration to improve the quality of secondary effluents in tertiary treatment and reuse

Unsatisfactory effluent purification, limited to secondary treatment, considerably restricts the reuse of treated water. In this study, the performance of three ceramic ultrafiltration (UF) membranes UF1 (0.02 μm), UF2 (0.05 μm), and UF3 (0.1 μm) was evaluated for the recovery of secondary effluent (SE) from a wastewater treatment plant (WWTP) in Kenitra. The effects of different parameters on treated water quality were assessed, including transmembrane pressure (TMP), circulation velocity (CV), and membrane pore size. The results indicated that the UF1 membrane was more effective than UF2 and UF3, achieving maximum removal rates for chemical oxygen demand (COD), biochemical oxygen demand at 5 days (DBO5), and total suspended solids (TSS) of 75%, 72%, and 96%, respectively, under optimal operating conditions of TMP at 1 bar and CV at 1 m/s. UF2 achieved removal rates of 70%, 71%, and 94% for COD, BOD5, and TSS, respectively, under the same conditions. For UF3, the highest removal rates were 64%, 62%, and 92% for COD, BOD5, and TSS, respectively, at 2 bar and 1 m/s. Moreover, the experiments also demonstrated that an increase in TMP results in increased permeate flux and fouling resistance, while CV has also an impact on the permeate flux. Additionally, a very satisfactory retention rate for microorganisms was observed, exceeding 90%, with no presence of helminth eggs (100% removal) detected in the treated water. Nutrient elimination was also notable, with reductions of 14% for total Kjeldahl nitrogen (TKN) and 50% for total phosphorus (TP) using the UF1 membrane, which was selected based on its optimal performance.

Bioconversion of organic wastes: treatment sludges, animal manures, and agricultural wastes

AbstractThis study aimed to investigate the compostability of treatment sludge and to determine the effects of adding different animal manures (cattle, pig, horse, and chicken) and agricultural waste (sunflower stalks) on the composting process. Five different compost reactors (M1, M2, M3, M4, and M5) were operated. Sunflower stalks were added to all reactors as a bulking agent at the rate of 20%. Treatment sludge (80%) and bulking agent were added to the M1 reactor, where animal manure was not added, while 40% treatment sludge and 40% animal manure were added to the other reactors. In the reactors where animal manure was added, cattle (M2), pig (M3), horse (M4), and chicken (M5) manure were used, respectively. The temperature, pH, electrical conductivity, organic matter (OM), carbon to nitrogen ratio (C/N), total Kjeldahl nitrogen, and total phosphorus were monitored during the 21-day process. The highest OM loss (64.8%) occurred in the M2 reactor, and the maximum temperature (62.7 °C) was achieved. The high temperatures reached in the reactor increased microbial activity, resulting in rapid decomposition of OM and elimination of pathogens. With a maximum reduction in the C/N ratio (40%), carbon and nitrogen balance was achieved, thus obtaining a more stable and higher quality compost for plants in this reactor. In the M1 reactor, where only treatment sludge was composted, lower microbiological activity occurred compared to the other mixtures due to the lack of substrate. It can be said that composting treatment sludge together with animal manures will provide higher quality end products.

Effect of hydrothermal pretreatment on leachate fed Scenedesmus sp. biomass solubilization and biogas production

The aim of the present study was to assess the effect of hydrothermal pretreatment on the solubilization and anaerobic digestion (AD) of Scenedesmus sp. biomass. At first, the microalgae was cultivated in 5% fresh leachate (FL) to recover nutrients such as nitrogen and phosphorus. Scenedesmus sp. grown in 5% FL obtained 100%, 77% and 97% removal efficiency of ammonium nitrogen (NH4+ - N), total Kjeldahl nitrogen (TKN) and phosphate phosphorous (PO43− -P), respectively. In the following step, the hydrothermal pretreatment of Scenedesmus sp. biomass was carried out at 120, 150 and 170 °C and retention time of 0, 30 and 60 min to evaluate its solubilization and biogas production through AD in batch test. Soluble chemical oxygen demand (sCOD) increased by 260% compared to untreated microalgae at 170 °C for 60 min. In comparison to untreated microalgae, the highest increase in biogas (70%) and methane yield (100%) was observed for 150 °C and 60 min pretreated microalgae as a consequence of hydrothermal pretreatment. Hydrothermal pretreatment has shown effectiveness in enhancing biomass solubilization and increasing biogas yield. Nevertheless, further research at the pilot scale is necessary to thoroughly evaluate the potential and feasibility of hydrothermal pretreatment for full-scale implementation.

Assessing environmental pollutionfrom shrimp farming activities in Soc Trang province

The study aimed to evaluate the level of environmental pollution from shrimp farming in coastal areas of Soc Trang province. A total of 10 shrimp farming households and 50 neighbouring households were interviewed about emissions and environmental sanitation conditions. At the end of the shrimp season, pond water samples were collected from 5 semi-intensive ponds and 5 intensive ponds, bottom sediment samples were collected from 5 semi-intensive ponds to evaluate the level of pollution. Interview results indicated that wastewater and bottom sediment from shrimp farming are the main causes of declining surface water quality and reducing the number of wild fish; pollution levels are likely to increase in the future. The pH, total suspended solid (TSS), BOD5, and chemical oxygen demand (COD) values of pond water samples are suitable for shrimp farming (except TSS of water samples in Cu Lao Dung and Long Phu); total Kjeldahl nitrogen (TKN) and total phosphorus (TP) contents fluctuate widely between sampling ponds. The metal content in the bottom sediment is lower than the allowable discharge threshold of sediment quality standards. Solid waste generated in farming areas has not been properly collected and treated. To sustainably develop the shrimp industry, local authorities need to encourage shrimp farmers to apply proper waste treatment technologies in addition to state management solutions.

Hybrid machine learning modeling of nitrogen removal from wastewater using gas-liquid-solid circulating fluidized bed riser

Municipal wastewater generally contains high amounts of nitrogen (N), approximately 23–28 mg/L of total Kjeldahl Nitrogen (TKN), which causes eutrophication and pollution of groundwater. This article reports the generation of empirical models for estimating the nitrogen removal efficacy of two outputs (NH4-N and NO3-N) from the anoxic riser of a highly efficient municipal wastewater treatment system involving a gas-liquid-solid circulating fluidized bed (GLSCFB) bioreactor. To identify the important variables and discard irrelevant ones, the ReliefF algorithm is applied initially. Out of 10 independent variables, this method indicates that only three, such as flow rate, total Kjeldahl Nitrogen (TKN), and downer effluent of NO3-N, are meaningful for anoxic nitrogen removal. Then, a hybrid Bayesian Optimization Algorithm and Support Vector Regression (BOA-SVR) is implemented, considering only the essential variables. In this regard, real-life laboratory data are utilized to develop the models. The BOA approach and k-fold cross-validation technique are explicitly applied to optimize the model's hyperparameters and avoid overfitting. The established models provided sufficiently accurate predictions via their comparisons to the experimental observations. Besides, the BOA-SVR model outperforms the classical multiple linear regression (MLR). The BOA-SVR models' forecasted results for both the predicted amount of NH4-N and NO3-N are favorably compared with the laboratory trials (R2> 99 %). A comprehensive evaluation is further conducted to validate the performance of this model by calculating the root mean square error, mean absolute percentage error, fractional bias, and computational efficiency. Gaussian white noise is used to add three distinct noise levels (20 %, 40 %, and 60 %) to the testing data to evaluate the model's robustness. Moreover, the plots of relative deviations and residuals were dispersed across the zero-reference line with moderate fluctuations. Sensitivity analysis indicated the relative importance of the three independent variables on the anoxic nitrogen removal in the order of influent TKN > downer effluent NO3-N >flowrate. Overall, the developed tool has substantial potential in modeling other convoluted processes.