Application of hybrid multi-criteria decision-making approach to analyze wastewater microalgae culture systems for bioenergy production.

Bioenergy generation from microalgae can significantly contribute to climate mitigation and renewable energy production. In this regard, several multi-criteria decision-making method were employed to prioritize appropriate microalgae culture system for bioenergy production. Entropy weight, Criteria Importance Through Intercriteria Correlation (CRITIC) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) were the employed MCDA method. Fourteen microalgae culture systems were selected as a case study, which contain teen monoculture and four dual-culture. Initially, through ans in-depth review of the literature and expert views, four categories total eight indicators were selected as the evaluation indices of the study, namely 1) Proliferation: Half growth cycle and Max growth rate,2) Biomass output: Bio-crude yield and Lipid yield, 3) Nutrient utilization: residual concentration of total Nitrogen and total Phosphorus, and, 4) Stability: coefficient of variation of Bio-crude yield and Lipid yield. The result indicated that "Pediastrum sp. & Micractinium sp." was identified as the most bioenergy potential microalgae culture system, and the evaluation results of entropy weight method and CRITIC method are similar. It is pertinent to note that 1)the entropy weight method exhibits lower sample size requirements, 2) the critic method excels when dealing with larger sample sizes, and 3) the TOPSIS method necessitates the incorporation of appropriate weighting methods to ensure credible results. In the application stage, the key indicators related to cost can be further included in the evaluation indices.

Effect of different bulking agents on fed-batch composting and microbial community profile.

The current study focused on analyzing the effect of different types of bulking agents and other factors on fed-batch composting and the structure of microbial communities. The results indicated that the introduction of bulking agents to fed-batch composting significantly improved composting efficiency as well as compost product quality. In particular, using green waste as a bulking agent, the compost products would achieve good performance in the following indicators: moisture (3.16%), weight loss rate (85.26%), and C/N ratio (13.98). The significant difference in moisture of compost products (p < 0.05) was observed in different sizes of bulking agent (green waste), which was because the voids in green waste significantly affected the capacity of the water to permeate. Meanwhile, controlling the size of green waste at 3-6 mm, the following indicators would show great performance from the compost products: moisture (3.12%), organic matter content (63.93%), and electrical conductivity (EC) (5.37 mS/cm). According to 16S rRNA sequencing, the relative abundance (RA) of thermophilic microbes increased as reactor temperature rose in fed-batch composting, among which Firmicutes, Proteobacteria, Basidiomycota, and Rasamsonia were involved in cellulose and lignocellulose degradation.

Time-varying characteristics of saturated hydraulic conductivity in grassed swales based on the ensemble Kalman filter algorithm -A case study of two long-running swales in Netherlands.

Saturated hydraulic conductivity (Ks) of the filler layer in grassed swales are varying in the changing environment. In most of the hydrological models, Ks is assumed as constant or decrease with a clogging factor. However, the Ks measured on site cannot be the input of the hydrological model directly. Therefore, in this study, an Ensemble Kalman Filter (EnKF) based approach was carried out to estimate the Ks of the whole systems in two monitored grassed swales at Enschede and Utrecht, the Netherlands. The relationship between Ks and possible influencing factors (antecedent dry period, temperature, rainfall, rainfall duration, total rainfall and seasonal factors) were studied and a Multivariate nonlinear function was established to optimize the hydrological model. The results revealed that the EnKF method was satisfying in the Ks estimation, which showed a notable decrease after long-term operation, but revealed a recovery in summer and winter. After the addition of Multivariate nonlinear function of the Ks into hydrological model, 63.8% of the predicted results were optimized among the validation events, and compared with constant Ks. A sensitivity analysis revealed that the effect of each influencing factors on the Ks varies depending on the type of grassed swale. However, these findings require further investigation and data support.

Potable and irrigation suitability of different water supply systems in riverine communities at river Cauvery distributaries, India.

Current study focused on investigating the pollution loads of open well, bore well and drinking water from riverine community sites. In addition, drinking and irrigation suitability assessment were also performed by using user specific water quality indices (USWQI) and parameters quality index (PQI). Principal component analysis (PCA) was also performed with physio-chemical parameters. Notable variation was found in most of the water quality parameters at major hamlet and some places exceeded the standards prescribed by authorized organizations. The USWQI was 97.53 to 38.15 in open wells, 96.06 to 68.23 in bore wells, and 88.64 to 74.16 in tap water (drinking water). Among the settlement, highest water quality was recorded at Vilangudi, while the lowest quality found in Karaipakkam area. The predominant drinking water samples were estimated as good quality for human health and hygiene whereas none of the sample was found to be excellent. Open and bore well water samples were of good quality and suitable for agriculture purposes except the few samples which were estimated as poor and fair quality.

Component design optimization of green roof substrate layer based on the assessment of multifunctional performance.

A high-quality substrate layer is the cornerstone of supporting that green roofs (GRs) can become an efficient and sustainable nature-based solution to urban environmental problems. In the present study, three lightweight substrate materials commonly used in GRs of peat soil, vermiculite and pumice with four appropriate proportions of the nutrient substrate and the mineral substrates were selected to install twelve substrate modules. The lightweight property, water-holding, nutrient retention and rainwater reduction performance of the substrate modules were investigated by the laboratory determination methods and the simulated rainfall experiment. An assessment model based on the multifunctional performance established by analytic hierarchy process (AHP) was used for the component design optimization of GR substrate layer. The results showed that the substrate modules based on peat soil and vermiculite (PV) as the mineral substrate, which the dry volumetric weights and the average water content were 1.40-1.70 kN m-3 and 47.80%-49.06%, always exhibited better lightweight properties and water-holding performance compared to those composed of pumice. PV-40 had the highest value of the multifunction index even while none of its functional performance was optimal among all the substrate modules. The present study emphasizes the necessity of optimizing the GR substrate layer component based on the assessment of multifunctional performance to better promote the sustainable development of GRs in urban areas.

Long-Term Dechlorination of Polychlorinated Biphenyls (PCBs) in Taihu Lake Sediment Microcosms: Identification of New Pathways, PCB-Driven Shifts of Microbial Communities, and Insights into Dechlorination Potential.

Microbial reductive dechlorination of polychlorinated biphenyls (PCBs) is regarded as an alternative approach for in situ remediation and detoxification in the environment. To better understand the process of PCB dechlorination in freshwater lake sediment, a long-term (108 weeks) dechlorination study was performed in Taihu Lake sediment microcosms with nine parent PCB congeners (PCB5, 12, 64, 71, 105, 114, 149, 153, and 170). Within 108 weeks, the total PCBs declined by 32.8%, while parent PCBs declined by 84.8%. PCB dechlorinators preferred to attack meta- and para-chlorines, principally para-flanked meta and single-flanked para chlorines. A total of 58 dechlorination pathways were observed, and 20 of them were not in 8 processes, suggesting the broad spectrum of PCB dechlorination in the environment. Rare ortho dechlorination was confirmed to target the unflanked ortho chlorine, indicating a potential for complete dechlorination. PCBs drove the shifts of the microbial community structures, and putative dechlorinating bacteria were growth-linked to PCB dechlorination. The distinct jump of RDase genes ardA, rdh12, pcbA4, and pcbA5 was found to be consistent with the commencement of dechlorination. The maintained high level of putative dechlorinating phylum Chloroflexi (including Dehalococcoides and o-17/DF-1), genus Dehalococcoides, and four RDase genes at the end of incubation revealed the long-term dechlorination potential. This work provided insights into dechlorination potential for long-term remediation strategies at PCB-contaminated sites.

A comprehensive review on the long-term performance of stormwater biofiltration systems (SBS): Operational challenges and future directions.

Stormwater biofiltration systems (SBS) are a popular technology for mitigating the negative effects of urbanization on the hydrological processes and water quality in urban areas. However, little is known about SBS's long-term performance in actual field conditions. The findings of a review of the scientific literature on the long-term performance of SBS are presented in this paper. The findings show that only a few studies have investigated the performance of SBS and its change over time, and that the results of laboratory and field experiments differed due to the presence of plants, regular maintenance, and some uncertain environmental factors. Based on the existing knowledge gaps in this field, the main challenges observed was the lack of long-term field data series, and the existing mathematical models are not able to accurately forecast the long-term performance of SBS. This could be owing to the difficulties in monitoring activities, the high costs involved and the unpredictability around the operational timeframe. Future study should concentrate on the implementation of simulation and modeling-based research in pilot and full-scale SBS, and the inclusion of new performance indicators should be considered as a priority.

Migration and transformation of nitrogen in sediment-water system within storm sewers.

In the sediment-water system of storm sewers (e.g., sediments, interstitial water, and the water column), the migration of nitrogen and its biological transformation with different dissolved oxygen conditions were investigated. Results showed that in an aerobic segment, γ-proteobacteria, α-proteobacteria, and nitrospira, which are aerobic, grew actively in water column and interstitial water through ammonification and nitrification. In anoxic segment, ammonification depended mainly on clostridia, whereas nitrification was inhibited. Thus, after 20 days, the concentration of NH4+-N in the aerobic segment became noticeably lower (5.97 mg/L) than that in the anoxic segment (18.09 mg/L). In sediments, the biological transformation of organic nitrogen in the anoxic environment was more complete, resulting in elevating amino acid nitrogen and NH4+-N in the anoxic segment compared to the aerobic segment. Furthermore, the concentration gradient of NH4+-N between interstitial water and water column in aerobic and anoxic segments, thereby causing NH4+-N to migrate from interstitial water to the water column. In the sediment-water system, the different forms of nitrogen changes were the common result of biological transformation and material migration.

Designing process and operational effect of modified septic tank for the pre-treatment of rural domestic sewage.

Structure and performance of a newly designed four-chamber septic tank were investigated in current study. A three-layer orifice plate was fitted in the first compartment in an upward direction, and a baffle was arranged in the second compartment of the septic tank. The filter placed in the third and fourth compartment was used to collect water for field irrigation or connect subsequent devices for further processing. Flow field distribution in the first chamber was numerically simulated by Fluent software, and simulation results were verified by residence time distribution tracer experiment. The improved treatment effects of the modified septic tank with optimal parameters of 20 mm (diameter), 60 mm (gap) and 180 mm (distance) were validated by simulation experiments. High removal rates of chemical and biological oxygen demand reflected the effectiveness of modified septic tanks.

Investigation on the carbon sequestration capacity of vegetation along a heavy traffic load expressway.

Carbon sequestration by vegetation plays an important role in the global carbon cycle. More emphasis on the carbon sequestration of roadside vegetation will help to reduce the total carbon emissions from the transportation sector. In the current study, the Shanghai-Nanjing G42 expressway in east China was selected to investigate and calculate the carbon sequestration of roadside vegetation including trees, shrubs and herbs. Findings of the current study revealed that the total carbon sequestration of all the vegetation was about 97,000 tons per year. Results also indicated that trees have a higher carbon sequestration capacity (γ) in unit land area compared to shrubs and herbs. The γ value of most of the shrubs was lower than that of tree; however, species such as Nerium indicum, Jasminum mesnyi and Forsythia suspense have better carbon sequestration capacity than some other tree species. The γ value of herbs was too low, compared with trees and shrubs. The findings of the current study will be of great benefit to make the vegetation planting strategy for express highways in the areas with similar geographic characteristics and climate.

Development and evaluation of MTLSER and QSAR models for predicting polyethylene-water partition coefficients.

Current study was aimed to make further improvements in measuring low density polyethylene (LDPE) -water partition coefficient (KPE-w) for organic chemicals. Modified theoretical linear solvation energy relationship (MTLSER) model and quantitative structure activity relationship (QSAR) model were developed for predicting KPE-w values from chemical descriptors. With the MTLSER model, α (average molecular polarizability), µ (dipole moment) and q- (net charge of the most negative atoms) as significant variables were screened. With the QSAR model, main control factors of KPE-w values, such as CrippenLogP (Crippen octanol-water partition coefficient), CIC0 (neighborhood symmetry of 0-order) and GATS2p (Geary autocorrelation-lag2/weighted by polarizabilities) were studied. As per our best knowledge, this is the first attempt to predict polymer-water partition coefficient using the MTLSER model. Statistical parameters, correlation coefficient (R2) and cross-validation coefficients (Q2) were ranging from 0.811 to 0.951 and 0.761 to 0.949, respectively, which indicated that the models appropriately fit the results, and also showed robustness and predictive capacity. Mechanism interpretation suggested that the main factors governing the partition process between LDPE and water were the molecular polarizability and hydrophobicity. The results of this study provide an excellent tool for predicting log KPE-w values of most common hydrophobic organic compounds, within the applicability domains to reduce experimental cost and time for innovation.

Sediment in-situ bioremediation by immobilized microbial activated beads: Pilot-scale study.

A field study was carried out to investigate the sediment in-situ bioremediation by adding microbial activated beads. In this work, Calcium carbonate, silicon dioxide, activated carbon powder, attapulgite powder, sodium alginate, microbial liquid and polyvinyl alcohol were utilized to make the immobilized microbial activated beads. Field experiment results showed that the removal rate of NH4+-N, TN and COD in overlying water reached about 61.8%, 87.5% and 87.1%, respectively. The initial concentration of NH4+-N, TN and COD was 159 mg/L, 6.24 mg/L and 7.28 mg/L, whereas and the final concentration was 58 mg/L, 0.78 mg/L and 0.94 mg/L when water temperature, DO, pH and C/N ratio were 25-30 °C, 2-3 mg/L, 7.0-8.0 and 10-15, respectively. Moreover, under optimal temperature condition (25-30 °C), the removal rate of TOC, TN, heterotrophic bacteria and sulfur bacteria in the river sediment reached to 46.5%, 50.7%, 39.2% and 73.2%, respectively.

Reducing nitrogen runoff from paddy fields with arbuscular mycorrhizal fungi under different fertilizer regimes.

Nitrogen (N) runoff from paddy fields serves as one of the main sources of water pollution. Our aim was to reduce N runoff from paddy fields by fertilizer management and inoculation with arbuscular mycorrhizal fungi (AMF). In northeast China, Shuangcheng city in Heilongjiang province, a field experiment was conducted, using rice provided with 0%, 20%, 40%, 60%, 80%, and 100% of the local norm of fertilization (including N, phosphorus and potassium), with or without inoculation with Glomus mosseae. The volume, concentrations of total N (TN), dissolved N (DN) and particulate N (PN) of runoff water were measured. We found that the local norm of fertilization led to 18.9kg/ha of N runoff during rice growing season, with DN accounting for 60%-70%. We also found that reduction in fertilization by 20% cut down TN runoff by 8.2% while AMF inoculation decreased N runoff at each fertilizer level and this effect was inhibited by high fertilization. The combination of inoculation with AMF and 80% of the local norm of fertilization was observed to reduce N runoff by 27.2%. Conclusively, we suggested that the contribution of AMF inoculation combined with decreasing fertilization should get more attention to slow down water eutrophication by reducing N runoff from paddy fields.

Calibration and application of an automated seepage meter for monitoring water flow across the sediment-water interface.

The advective flow of sediment pore water is an important parameter for understanding natural geochemical processes within lake, river, wetland, and marine sediments and also for properly designing permeable remedial sediment caps placed over contaminated sediments. Automated heat pulse seepage meters can be used to measure the vertical component of sediment pore water flow (i.e., vertical Darcy velocity); however, little information on meter calibration as a function of ambient water temperature exists in the literature. As a result, a method with associated equations for calibrating a heat pulse seepage meter as a function of ambient water temperature is fully described in this paper. Results of meter calibration over the temperature range 7.5 to 21.2 °C indicate that errors in accuracy are significant if proper temperature-dependence calibration is not performed. The proposed calibration method allows for temperature corrections to be made automatically in the field at any ambient water temperature. The significance of these corrections is discussed.

Effect of saponin on the phytoextraction of Pb, Cd and Zn from soil using Italian ryegrass.

Chemically enhanced phytoextraction has been proposed as an effective approach to remove metals from contaminated soil through the Italian ryegrass (Lolium multiflorum Lam.). The bioconcentration factor (BCF) and translocation factor (TF) are important determinants for phytoextraction of metals. In microcosm experiments, effects of saponin on the uptake of Pb, Zn and Cd by Italian ryegrass were studied. Results of BCF indicated that Italian ryegrass was the most efficient in Zn uptake, followed by Cd and Pb (Zn > Cd > Pb). TF results were identical to the BCF results. In addition, the effect of metal stress on antioxidative enzyme activity was studied. Results revealed that under the metal stress, saponin played an important role in the antioxidative activities of Italian ryegrass.

Effect evaluation of different green wastes on food waste digestate composting and improvement of operational conditions.

This study attempted to determine the influence of diverse green wastes on food waste digestate composting and the improvement of operational conditions. Various effects of the green wastes (GW), with different types and sizes, initial substrate mixture C/N ratios, compost pile heights, and turning frequencies on the food waste digestate (FWD) composting were examined in the current work. The findings showed that the use of street sweeping green waste (SSGW) as an additive can maintain the thermophilic stage of the FWD composting for 28 days, while the end-product contained the greatest amounts of total phosphorus (TP, 2.29%) and total potassium (TK, 4.61%) and the lowest moisture content (14.8%). Crushed SSGW (20 mm) enabled the FWD composting to maintain the longest thermophilic period (28 days), achieving the highest temperature (70.2 °C) and seed germination index (GI, 100%). Adjusting the initial substrate mixture C/N ratio to 25, compost pile height to 30 cm, and turning frequency to three times a day could enhance the efficiency and improve the fertilizer quality of the co-composting of the FWD and SSGW. This study suggested that co-composting of FWD and SSGW (FWD/SSGW = 2.3, wet weight) is a promising technique for the treatment of municipal solid waste and provided significant theoretical data for the application of composting.

Screening of representative rainfall event series for long-term hydrological performance evaluation of grassed swales.

Evaluation of the hydrological performance of grassed swales usually needs long-term monitoring data. At present, suitable techniques for simulating the hydrological performance using limited monitoring data are not available. Therefore, current study aims to investigate the relationship between saturated hydraulic conductivity (Ks) fitting results and rainfall characteristics of various events series length. Data from a full-scale grassed swale (Enschede, the Netherlands) were utilized as long-term rainfall event series length (95 rainfall events) on the fitting outcomes. Short-term rainfall event series were extracted from these long-term series and used as input in fitting into a multivariate nonlinear model between Ks and its influencing rainfall indicators (antecedent dry days, temperature, rainfall, rainfall duration, total rainfall, and seasonal factor (spring, summer, autumn, and winter, herein refer as 1, 2, 3, and 4). Comparison of short-term and long-term rainfall event series fitting results allowed to obtain a representative short-term series that leads to similar results with those using long-term series. A cluster analysis was conducted based on the fitting results of the representative rainfall event series with their rainfall event characteristics using average values of influencing rainfall indicators. The seasonal index (average value of seasonal factors) was found to be the most representative short rainfall event series indicator. Furthermore, a Bayesian network was proposed in the current study to predict if a given short-term rainfall event series is representative. It was validated by a data series (58 rainfall events) from another full-scale grassed swale located in Utrecht, the Netherlands. Results revealed that it is quite promising and useful to evaluate the representativeness of short-term rainfall event series used for long-term hydrological performance evaluation of grassed swales.

Integrating molecular descriptors for enhanced prediction: Shedding light on the potential of pH to model hydrated electron reaction rates for organic compounds.

Hydrated electron reaction rate constant (ke-aq) is an important parameter to determine reductive degradation efficiency and to mitigate the ecological risk of organic compounds (OCs). However, OC species morphology and the concentration of hydrated electrons (e-aq) in water vary with pH, complicating OC fate assessment. This study introduced the environmental variable of pH, to develop models for ke-aq for 701 data points using 3 descriptor types: (i) molecular descriptors (MD), (ii) quantum chemical descriptors (QCD), and (iii) the combination of both (MD + QCD). Models were screened using 2 descriptor screening methods (MLR and RF) and 14 machine learning (ML) algorithms. The introduction of QCDs that characterized the electronic structure of OCs greatly improved the performance of models while ensuring the need for fewer descriptors. The optimal model MLR-XGBoost(MD + QCD), which included pH, achieved the most satisfactory prediction: R2tra = 0.988, Q2boot = 0.861, R2test = 0.875 and Q2test = 0.873. The mechanistic interpretation using the SHAP method further revealed that QCDs, polarizability, volume, and pH had a great influence on the reductive degradation of OCs by e-aq. Overall, the electrochemical parameters (QCDs, pH) related to the solvent and solute are of significance and should be considered in any future ML modeling that assesses the fate of OCs in aquatic environment.

Pilot-scale membrane-covered composting of food waste: Initial moisture, mature compost addition, aeration time and rate.

The impact of different operational parameters on the composting efficiency and compost quality during pilot-scale membrane-covered composting (MCC) of food waste (FW) was evaluated. Four factors were assessed in an orthogonal experiment at three different levels: initial mixture moisture (IMM, 55 %, 60 %, and 65 %), aeration time (AT, 6, 9, and 12 h/d), aeration rate (AR, 0.2, 0.4, and 0.6 m3/h) and mature compost addition ratio (MC, 2 %, 4 %, and 6 %). Results indicated that 55 % IMM, 6 h/d AT, 0.4 m3/h AR, and 4 % MC addition ratio simultaneously provided the compost with the maximum cumulative temperature and the minimum moisture. It was shown that the IMM was the driving factor of this optimum composting process. On contrary, the optimal parameters for reducing carbon and nitrogen loss were 65 % IMM, 6 h/d AT, 0.4 m3/h AR, and 2 % MC addition ratio. The AR had the most influence on reducing carbon and nitrogen losses compared to all other factors. The optimal conditions for compost maturity were 55 % IMM, 9 h/d AT, 0.2 m3/h AR, and 6 % MC addition ratio. The primary element influencing the pH and electrical conductivity values was the AR, while the germination index was influenced by IMM. Protein was the main organic matter limiting the composting efficiency. The results of this study will provide guidance for the promotion and application of food waste MCC technology, and contribute to a better understanding of the mechanisms involved in MCC for organic solid waste treatment.

How internal nutrient loading forms in shallow lakes: Insights from benthic organic matter mineralization.

Internal nutrient loading in shallow lakes has long been known as a key driver of eutrophication, especially after external loading reductions. Earlier efforts have been made to quantity the size and potential release of internal nutrient pools in lakes. Yet, links among substrates, microbial processes, and the size and actual release of internal nutrient pools remain largely unclear. To assess the links, sediment organic matter in Lake Taihu, China, was characterized by combining optical measurements, and lake-wide sediment gross nitrogen (N) transformations were measured using the stable isotope (15N) dilution technique. Meanwhile, respirations and nutrient fluxes across the sediment-water interface (SWI) were measured by conducting intact core continuous-flow incubations. The cause-effect relationships among sediment physicochemical parameters (especially organic matter properties), gross N transformations, extractable nutrient concentrations, and nutrient fluxes across the SWI were revealed by partial least square path models. Results showed that environmental controls on the N transformation rates at different seasons varied, with sediment-derived dissolved organic matter abundance being more important than other variables in driving the rates during summer blooms. This study put a step toward revealing the significant positive effects of sediment organic matter mineralization on porewater nutrient concentrations and then on nutrient fluxes across the SWI at late season. The significant positive correlation between the gross N mineralization rates and ammonium fluxes across the SWI and the estimated considerable volume of net N mineralization in summer further suggested that algal blooms can get substantial inorganic N from sediment N mineralization during the lake N limitation period. Overall, this paper presents new insights into the substrates- and microbial process-driven internal nutrient loading of shallow lakes, which is the fundamental driving force of internal nutrient loading formation.