Pollution Reduction Efficiency Research Articles

Carbon emission trading, technological progress, synergetic control of environmental pollution and carbon emissions in China

This study introduces three production technology shocks (Energy manufactures, Brown enterprises, and Green enterprises) by constructing different models, namely, the environment sector (baseline) model, the carbon emissions trading scheme (ETS) model, and the carbon emissions rights trading mechanism. The fluctuation trend of China's macroeconomic and environmental quality before and after the establishment of carbon market is compared and analyzed. Additionally, the study examines the welfare of the implementation of carbon market policies. The carbon trading market policy can promote the synergistic efficiency of China's pollution reduction and carbon reduction using energy and green production technologies. From the perspective of social welfare, the optimal range of the initial carbon quota ratio issued by the government to enterprises is [0.7,0.8]. The findings of this study provide theoretical support and contribute toward understanding the impact mechanisms of carbon market and technological progress on synergizing the reduction of pollution and carbon emissions in China.

Spatial pattern and driving factors of synergistic governance efficiency in pollution reduction and carbon reduction in Chinese cities

This paper is based on the construction of the evaluation system of urban pollution reduction and carbon reduction synergistic governance efficiency indicators. Firstly, we used the NDDF model to measure the efficiency of urban pollution reduction and carbon reduction synergistic governance. We then used the ArcGIS technology and spatial autocorrelation method to explore its spatial distribution pattern, and the spatial econometric model is used to explore its driving factors. The results show that from 2006 to 2020, the synergistic governance efficiency of Chinese cities in terms of pollution reduction and carbon reduction is in a state of continuous improvement, with an increase of 38.07 per cent in 2020 compared with 2006, and overall the synergistic governance efficiency of cities in terms of pollution reduction and carbon reduction shows a pattern of development in which the east is high and the west is low, but there is a tendency for the gap to narrow from one year to the next. There is a positive spatial aggregation of urban pollution reduction and carbon synergistic governance efficiency, which is further shown by the Lisa aggregation diagram that the spatial aggregation of urban pollution reduction and carbon synergistic governance efficiency in China is characterized by urban agglomerations, with the high and high aggregation zones being concentrated in the central and eastern urban agglomerations, such as the urban agglomerations of the middle reaches of the Yangtze River and Guangdong-Fujian-Zhejiang, and the low and low aggregation zones being concentrated in the western urban agglomerations, such as the Lanzhou-Western urban agglomerations and the Guanzhong Plain urban agglomerations. The results of the SDM model indicate that the efficiency of urban pollution reduction and carbon synergistic governance can significantly promote the process of pollution reduction and carbon synergistic governance in neighboring areas. The six drivers, namely, industrial structure, economic development level, innovation level, urbanization rate, population size and foreign direct investment, all have a significant impact on the efficiency of urban pollution reduction and carbon synergistic governance in a local area. The spatial spillover effects of the remaining variables, except for urbanization rate, on the efficiency of urban pollution reduction and carbon synergistic governance are significantly negative. Based on this, corresponding countermeasures are proposed to improve the synergistic governance of urban pollution reduction and carbon reduction.

Cooling and purification effect of permeable pavements

Abstract Permeable pavement is a widely used stormwater runoff blocking technology in sponge city construction. Its application to urban motorized/non-motorized roads is expected to reduce runoff and pollution loads. This study aimed to analyze the nutrient pollution, thermal pollution reduction efficiency and removal pathways of cement permeable bricks (CP-B-Cement), steel slag permeable bricks (SP-B), ceramic permeable bricks (CP-B-Ceramic) and permeable asphalt pavement (PAP) under different pollution loads and rainfall intensities by simulating the different stormwater runoffs. Results indicated that the effluent concentration of different permeable pavements increased with the extension of rainfall duration. Compared with impermeable pavements, the infiltration and water storage capacities of permeable pavements could effectively remove typical pollutants from stormwater runoff. However, the effluent concentrations of all pollutants did not reach the threshold of Class V according to the Environmental Quality Standards for Surface Water except for TP and Zn. Meanwhile, the thermal pollution removal capacity of the permeable pavements ranking from the highest to the lowest was SP-B > CP-B-Cement > CP-B-Ceramic > PAP. The findings in this study provide references for the selection of stormwater source reduction facilities and the development of surface source pollution countermeasures.

Comparative analysis of energy efficiency of electrostatic precipitator before and after ultralow emission in coal‐fired power plants in China

AbstractElectrostatic precipitator (ESP) is the main equipment for flue dust control of coal‐fired power plants in China, accounting for about 70% of the total currently. In this paper, energy efficiency data of ESP, including 202 sets before ultra‐low emission and 45 sets after ultra‐low emission are systematically studied and analyzed by using the research method of field testing and technical investigation. The results showed that after ultra‐low emission, the energy consumption and converted CO2 emission of ESP in coal‐fired power plants increased significantly, and the specific power consumption and energy consumption corresponding to unit mass particulate matter (PM) removal increased by 49.61% and 139%, respectively, and the converted CO2 emission increased by 1.67 × 10−4 kg CO2/m3 and 31.12 kg CO2/t PM on average. The energy consumption of low‐low‐temperature ESP (LLT‐ESP) was positively correlated with its emission reduction range. Before and after the gas cooler operation, the power consumption, specific power consumption and energy consumption corresponding to unit mass PM removal increased by 8.06%–38.68%, 10.66%–60.14% and 7.23%–62.98%, respectively, and the CO2 emissions corresponded increased by 26.29–691.81 kg CO2/h, 0.46–2.18×10−4 kg CO2/m3, 1.10–23.62 kg CO2/t PM, respectively. LLT‐ESP had a great possibility to optimize the operation for energy‐saving and carbon‐reduction, because when the high voltage power supply operated on the maximum output mode and the energy‐saving mode, the drop of power consumption and specific power consumption was around 52.00%–58.23%, 52.02%–58.29%, respectively, and the CO2 emission reductions corresponded was 1,039.25–1,359.35 kg CO2/h, 2.71–3.58×10−4 kg CO2/m3, respectively. LLT‐ESP also had the great optimizing possibility for energy‐saving and carbon‐reduction during low load operation, as when the load reduced from 100% to 50%, the specific power consumption and energy consumption corresponding to unit mass PM removal increased by 5.05%–45.50%, 6.59%–63.90%, respectively, and the CO2 emissions corresponded increased by 0.38–2.44×10−4 kg CO2/m3, 6.76–45.98 kg CO2/h, respectively. The operation energy consumption can be effectively reduced by integrated use of multiple electric dust removal technologies, such as compared with LLT‐ESP technology, the power consumption, specific power consumption and energy consumption corresponding to unit mass PM removal of “low‐low‐temperature + moving electrode+ electrostatic agglomeration” decreased by 37.88%, 30.08% and 45.29% respectively, and the corresponding CO2 emission decreased by 697.22 kg CO2/h, 1.87×10−4 kg CO2/m3 and 32.98 kg CO2/t PM, respectively. The current national standard GB 37484‐2019 is no longer applicable to the energy efficiency evaluation of the ESP in ultra‐low emission units. This study can provide data support for the revision of national standard GB 37484‐2019 and the collaborative efficiency of coal power plant pollution reduction and carbon reduction. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Multi-scale Analysis and Synergistic Scenario Simulation of Pollution and Carbon Reduction Efficiency in Guangdong-Hong Kong-Macao Greater Bay Area

In the context of China’s “double carbon” goal, pollution and carbon reduction is a consensus. As a demonstration area and model area for China’s development, how to take the lead in realizing the synergistic improvement of pollution and carbon reduction and embark on a green and low-carbon development path with Chinese characteristics is a common concern of the scientific community and the public. However, each city in Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is different regarding resource endowment, energy structure, development conditions, and technical level. The efficiency, ability, and potential of pollution and carbon reduction must differ. The mission objectives, methods, and methods of promoting the “double carbon” work are also different. Only by considering it from the perspective of system collaboration can the “double carbon” work be safe and sustainable. The study proposes that we can, from the dynamic perspective of the production network and industrial transfer, integrate multi-source and multi-mode data and use a multi-scale evaluation method to analyze the multi-dimensional features and driving factors of the interaction effect of pollution and carbon reduction in GBA. The research results can help cities in GBA to understand their weak links in pollution and carbon reduction in a timely, comprehensive, and accurate manner. In addition, this study is conducive to providing decision-making reference for China to formulate regional synergistic effects.

Analysis of Thermal Pollution Reduction Efficiency of Bioretention in Stormwater Runoff under Different Rainfall Conditions

The thermal pollution of stormwater runoff is an important factor in the degradation of the urban water environment. Bioretention is an effective way to control the thermal pollution of stormwater runoff. To understand the influence of different rainfall conditions on the reduction of thermal pollution load of rainwater runoff from bioretention facilities and the correlation between the parameters, an experimental study was carried out by using the Beijing P&C rainfall pattern to change the rainfall parameters. By proposing innovative evaluation index parameters and analysis methods, the correlation between different parameters was quantified. The results showed that the heat pollution load reduction rate (HR) had a strong negative correlation with rainfall inflow volume (IV), rainfall duration (RD), and the service area ratio of bioretention facilities (CAR), and the correlation coefficients were −0.95, −0.73, and −0.73, respectively. HR was weakly correlated with rainfall return period (RP), rainfall temperature (RT), and air temperature (At) during the experiment, and the correlation coefficients were −0.29, 0.20, and 0.20, respectively. The delay between the peak value of heat output from the bioretention and the peak value of heat input from rainfall was about 10 min. Through the research on the change of rainwater heat entering and exiting the facility, we can master some rules of heat reduction in bioretention facilities, which will provide a reference for subsequent research on the difference between the internal heat change and bioretention temperature change.

RESEARCH NEEDS IN AGRICULTURE AND OTHER LAND USES IN RESPONSE TO THE GREEN ECONOMY: A REVIEW

The United Nations Environment Programme defines a green economy as low-carbon, resource-efficient, and socially inclusive. The objective is to improve human well-being and social equity while significantly reducing environmental risks and ecological scarcity. The green economy is sustainable development without degrading the environment, developing around climate change, saving resources and management, circular economy, environmental and ecosystems protection, and natural disaster management and recovery. This paper aims to introduce discussions and brainstorm a way forward on how the Papua New Guinea University of Technology (PNGUoT) can use the expertise and resource centers and the technologies that are available to promote sustainable land and resource use and sustainable development; committing carbon emissions and pollution reduction, energy and resource use efficiency, and prevention of loss of biodiversity and ecological services. The specific roles of the PNGUoT in committing and contributing to sustainable development in agriculture, forestry, and fisheries are pointed out to improve rural livelihood. Several user-friendly sustainability concepts that are easy to promote by researchers are established as the way forward into the future.

A quantitative study on deposited fuel film and microscopic droplet characteristics of gasoline surrogate fuel and ethanol spray impingement

By applying down-sizing and high-pressure injection on gasoline direct injection (GDI) and dual-fuel spark ignition (DFSI) engines, the deposited fuel film caused by spray impingement would significantly increase engine soot emissions. In this study, laser-induced fluorescence (LIF) was used to initially explore the difference in deposited fuel film of gasoline surrogate fuel (GSF) and ethanol spray impingement. And, phase doppler anemometry (PDA) was used to further reveal the difference in deposited film formation mechanisms by analysing microscopic droplet characteristics quantitatively. The study could contribute novel insights to the fuel injection strategy optimisation, spray modelling research, pollution reduction and thermal efficiency improvement for GDI and DFSI engines. The results showed that 60% to 70% mass of the ethanol spray would deposit on the wall when vertical impingement, while that of GSF only is 40% to 60%. Moreover, due to ethanol's high viscosity, ethanol film is at least 39% thicker than GSF under the same injection condition. Thicker average film thickness easily results in pool fire and high soot emissions. Inclined impingement angle and high injection pressure could help reduce the deposited film mass of both fuels. Particularly, the film mass of GSF would decrease by 36% by increasing injection from 7 MPa to 15 MPa. Regarding microscopic droplet characteristics, a considerable difference can be seen for the incident droplets in different radial positions. Compared to ethanol, GSF spray droplet velocity is at least 13% higher, which would further enhance the reflection and secondary breakup.

Integrating synergistic control of pollutants and carbon dioxide into “Three Lines and One Permit” in China

In recent years, the impact of climate change on human society has become a popular research topic worldwide. To mitigate climate change, China established carbon emission peak and neutrality targets. Therefore, the synergistic control of pollutants and carbon dioxide has become a key objective for ecological and environmental protection in China. The “Three Lines and One Permit” (TLOP) system is an important policy that aims to increase environmental protection at the source and to integrate the advancement of high-quality development and high-level environmental protection. By integrating the synergetic control of pollutants and carbon dioxide into TLOP, planners and decision-makers may be better able to highlight the importance of carbon emission reduction and environmental quality management during the policy and planning stages. Therefore, by approaching the challenges associated with synergistic control of pollutants and carbon dioxide, this study explored the technical framework by combining the technical route and working basis of TLOP and clarified the appropriate technical methods and indicators. This study proposed a concrete path to achieving synergistic efficiency of pollution and carbon reduction in terms of ecological space, the Bottom Line of Atmospheric Environment Quality (BLAEQ), the Upper-limit Line for Energy Use (ULEU), the Integrated Environmental Unit (IEU) and the List of Environmental Permits for human activities (LEP). To promote the application of the technical framework, the research suggested that application should be performed from the following aspects: incorporating the TLOP into relevant laws, strengthening application between departments, and establishing a regional system.

Investigating the role of international industrial transfer and technology spillovers on industrial land production efficiency: Fresh evidence based on Directional Distance Functions for Chinese provinces

Participation in international industrial transfer (IIT) provides a significant opportunity and a motivation to improve China's industrial land production efficiency (ILPE). This study aims to investigate the overall role, heterogeneous impact and indirect mechanism of IIT in improving Chinese ILPE. This paper uses the Directional Distance Functions - Data Envelope Analysis (DDF-DEA) model to measure ILPE, economic output efficiency, and pollution reduction efficiency, the Global Malmquist Luenberger (GML) index to decompose the growth of ILPE into “technical efficiency change (EC)” and “technological change (TC)”. The panel data of Chinese provinces from 2003 to 2018 and the Fixed-Effect model is used to examine the impact of IIT on ILPE. The primary outcomes suggest that participation in IIT has generally improved the ILPE in China. This promotion effect is evident after 2010, and IIT has a significant impact on the improvement of ILPE in extensive and inefficient areas. Similarly, IIT promotes the economic output efficiency of industrial land from the perspective of expected output and reduces unexpected output. This impact helps in improving pollution reduction efficiency of industrial land. The technology spillover brought by IIT improves the Chinese ILPE from two channels, including promoting technological progress and improving technical efficiency. However, the technology spillover mainly promotes the ILPE in land use high-efficient areas by promoting technological progress. Likewise, the ILPE is promoted by improving technical efficiency from a regional perspective in extensive and inefficient areas. This study provides valuable insights for the improvement of ILPE to optimize land resources.

Introduction of IoT-Based Surrogate Parameters in the Ex-Post Countermeasure of Industrial Sectors in Integrated Permit Policy

New approaches and techniques are required for environmental management in workplaces that emit pollutants. The best available techniques (BATs) that are suggested by the integrated environmental permit system (IEPS) play a pivotal role in providing state-of-the-art approaches and techniques to workplaces. For the workplaces that install facilities with the BATs, it is necessary to perform real-time monitoring to determine whether pollutant emission facilities and treatment facilities are operating normally and whether such facilities can maintain the optimal condition during the emission of pollutants. The environmental management measures used before the IEPS had limitations for workplaces that are subjected to integrated environmental management because they consider the entire workplace as a single pollution source by combining all media. In addition, only the emission concentrations and amounts of pollutants were monitored because only the points at which most pollutants are discharged, i.e., stacks for air pollutant emission facilities and final effluent outlets for water pollutant emission facilities, are monitored. These monitoring approaches in a variety of facilities involve considerable costs, and most of them (95% for stacks in workplaces under IEPS, Korea) cannot perform real-time observation even though some of them are capable of it (5% for stacks managed by Tele Monitoring System, TMS). In this study, the applicability of a wireless sensor monitoring network was examined as a new approach for environmental management in workplaces. Based on the sensor monitoring network, surrogate parameters that can indirectly monitor the critical operating factors of pollutant emission and prevention facilities were developed and then measured in real time to examine the status of these facilities. Surrogate parameters can be used instead of directly measuring pollutants as the former has high efficiency, such as cost reduction, and can provide reliable data on the emission characteristics of pollutants. The wireless network is based on an Internet of Things (IoT) platform under real-time conditions in the emission and production facilities in a workplace. This study suggested that a wireless network using the IoT platform improves the BAT assessment methodology to understand the efficiency of environmental pollution reduction and the economic contribution to the workplace.

Green at source: an empirical examination of the effectiveness and sustainability of operational-level environmental management practices in U.S. industry

In this study, we examine the effectiveness of operational-level environmental management (EM) practices and their long-term impacts. Using data from the U.S. Environmental Protection Agency (EPA)’s Toxic Release Inventory, we assess how different source reduction practices utilised at the operational processes of U.S. industrial facilities affect their environmental performance. We find that those operational-level EM practices have varying impacts on immediate and long-term environmental improvements. Practices such as good operating practices, inventory control, process modification, spill/leak prevention, and cleaning/degreasing procedures are found to be able to help facilities improve their efficiency in pollution and waste reduction in the year of implementation. Additionally, good operating practices and spill/leak prevention can generate continuous improvement in pollution and waste reduction even after the implementation year. But at the facilities that adopt process modifications and cleaning/degreasing procedures, the improvements achieved from initial adoption can only be maintained at the same level afterwards. Moreover, the EM practice of inventory control only possesses temporary effectiveness limited to the implementation year while the efficiency of pollution and waste reduction at the facilities that applied this practice fell back to the level before the implementation. The implications of the results are discussed.

Impact of pH on Pollutional Parameters of Textile Industry Wastewater with Use of Chlorella pyrenoidosa at Lab‐Scale: A Green Approach

The current study focused on the pollution remediation of textile industry wastewater by using Chlorella pyrenoidosa in two different physical forms: free algal biomass and immobilized algal biomass. The hypothesis behind the present study was to analyze the pollution reduction efficiency of immobilized algal biomass and free algal biomass on comparative scale on the basis of the adsorption process which is directly proportional with the surface area of the adsorbate. So, in this context the immobilized form of algae could enhance the pollution reduction efficiency due to availability of more surface area. So, the textile industry wastewater was treated by both free algal biomass and immobilized algal biomass and the major wastewater contributors like nitrate, phosphate, Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were assessed before and after the treatment process. To conclude the optimum comparative results, the pH of wastewater was maintained constant, as it can capitalize or moderate the adsorption process (initial pH of was 8.2 ± 0.1, but it was maintained to 8). The contamination remediation was found to be effective with immobilized algal biomass (46.7% of nitrate, 59.4% of phosphate, 83.1% BOD and 83.0% of COD) than free algal biomass (43.2% of nitrate, 56.7% of phosphate, 71.4% of BOD and 78.0% COD).

Evaluation of coal mine pollution abatement benefit based on analytic hierarchy process

Due to the high energy consumption of China’s industrial structure, this has led to serious environmental pollution; in order to improve the efficiency of coal mine pollution reduction, the application of the basic principle of analytic hierarchy process (AHP) was used to select the evaluation index of coal mine pollution reduction, coal mine pollution reduction project, environment benefit evaluation, and target layer analysis. This paper takes the benefit composition and characteristics of coal mine pollution emission reduction project as the entry point, and the actual situation of coal mine pollution emission reduction as the basis; constructs the comprehensive evaluation model of technical and environment benefits of coal mine pollution emission reduction project; and establishes the corresponding comprehensive evaluation system. Through the case study of a mining area, the scientificity, practicality, and feasibility of the index system design are tested.

Impacts of industrial agglomeration on pollution and ecological efficiency-A spatial econometric analysis based on a big panel dataset of China’s 259 cities

In theory, the environmental positive externality of industrial agglomeration should be larger than its negative externality. However, from China’s reality, regions with a higher degree of industrial agglomeration often face various environmental problems, which raises the question whether industrial agglomeration helps or inhibits environmental quality improvement. Based on a big panel dataset of 259 cities from 2007 to 2016, this paper empirically tests the impacts of industrial agglomeration on pollution and ecological efficiency as well as the multidimensional urban heterogeneity using the spatial Durbin model. Moreover, it investigates the pollution reduction and green development effects by the common agglomeration of industry and services. We found that industrial agglomeration, pollution, and ecological efficiency have significant spatial spillover effects, with the agglomeration presenting a significant inverted U-shaped relationship with discharged wastewater, sulfur dioxide emission, and soot (dust) emission, and a significant U-shaped relationship with ecological efficiency. These results indicate that when the agglomeration level exceeds an inflection point, the agglomeration can generate pollution reduction and ecological efficiency improvement effects. Furthermore, the impacts of industrial agglomeration on pollution and ecological efficiency demonstrate obvious urban heterogeneity. In general, the "agglomeration inflection point" of eastern, large-sized, and major cities for environmental protection is smaller than that of central and western, medium-and small-sized, and non-major cities for environmental protection, respectively. In addition, the agglomeration among complementary and related industries can generate a noticeable pollution reduction effect, especially the common agglomeration of industry and producer services can effectively improve the coordination of economy, resources, and environment.

Dynamic and network slack-based measure analysis of China’s regional energy and air pollution reduction efficiencies

Abstract China’s rapid development over the past few decades has resulted in significant environmental pollution from CO2, SO2 and NO2 emissions amongst others, all of which can adversely affect human health. However, past efficiency analyses have tended to discuss energy efficiency and environmental efficiency separately, or have discussed ways in which governments can reduce pollution at the source. In other words, previous analyses of China’s energy efficiency have only been focused on one-stage, and very few studies have integrated the environment, government pollution reductions, and economic development in the analysis. Therefore, to fill this research gap, this study examined the first and second-stage energy and air pollution reduction efficiencies in thirty Chinese provinces and municipalities from 2013 to 2016 using a dynamic, network slack-based measure (DNSBM) model, in which labor, fixed assets and energy consumption were the input variables in the first production stage, GDP was the output variable, and CO2, SO2, and NO2 emissions were the link variables, and in the second treatment stage, pollution treatment investment was the input variable, the CO2, SO2, and NO2 emissions reductions were the output variables, and energy consumption/GDP was the carryover variable. It was found that; (1) Beijing, Shanghai, Guizhou, Hainan and Qinghai had the best performances over the 4 years, and Shaanxi, Shandong, Fujian, Jilin, Liaoning and Xinjiang had the worst performances and therefore had the greatest need for improvements; (2) the overall provincial efficiencies were generally relatively low and significant improvements were needed however, there were large differences between the provinces/municipalities; (3) the overall air pollution reduction efficiency governance in the second stage was low, indicating that more effective measures were needed to improve environmental efficiency and that the dynamic developments in government regulations and governance had resulted in a policy implementation lag; and (4) in 21 provinces, the first-stage productivity was significantly higher than the second-stage treatment productivity, indicating that the treatment stage needed to be strengthened.

Treatment of Balili River in Benguet, Philippines with constructed wetland planted with dominant local macrophytes

Phytoremediation using local macrophytes was explored in Balili River, Philippines. The macrophytes used were Amaranthus spinosus, Eichhornia crassipes, Eleusine indica and Pennisetum purpureum planted in pilot-scale constructed wetlands and subjected to varying hydraulic retention time (HRT) treatments. Results showed that these macrophytes have high phytoremediation performance in almost all water quality parameters. Also, HRT significantly affected the pollution reduction efficiency of the macrophytes. Significant pollution reduction was observed as early as HRT 1 day, but the optimal HRT for all the macrophytes was 3–4 days. At optimal HRT, the pollution reduction efficiency of the four macrophytes ranged from 96% to 99.9% for TSS, 87% to 95% for BOD, 85% to 99% for NO3, 85% to 96% for PO4 and 99.9% for total and fecal coliform. Also, Hg and Pb were significantly reduced. Results of TSS, DO and NO3 passed the water quality standard, while BOD and PO4 were slightly above. But total and fecal coliform, amidst the high reduction rate, was still not within the permissible level for Class A water. Among the macrophytes, P. purpureum generally have the best pollution reduction efficiency. Our study revealed comparable or even better pollution reduction efficiency of local macrophytes than commonly used ones such as Phragmites spp. and Typha spp.

Identification of Critical Source Areas (CSAs) and Evaluation of Best Management Practices (BMPs) in Controlling Eutrophication in the Dez River Basin

Best Management Practices (BMPs) are commonly used to control pollution in the river basins. Prioritization of BMPs helps improve the efficiency and effectiveness of pollution reduction, especially in Critical Source Areas (CSAs) that produce the highest pollution loads. Recently, the Dez River in Khuzestan, Iran, has become highly eutrophic from the overuse of fertilizers and pesticides. In this basin, dry and irrigated farming produce 77.34% and 6.3% of the Total Nitrogen (TN) load, and 83.56% and 4.3% of the Total Phosphorus (TP) load, respectively. In addition, residential, pasture, and forest land uses together account for 16.36% of the TN and 12.14% of the TP load in this area. The Soil and Water Assessment Tool (SWAT) was implemented to model the Dez River basin and evaluate the applicability of several BMPs, including point source elimination, filter strips, livestock grazing, and river channel management, in reducing the entry of pollution loads to the river. Sensitivity analysis and calibration/validation of the model was performed using the SUFI-2 algorithm in the SWAT Calibration Uncertainties Program (SWAT-CUP). The CSAs were identified using individual (sediment, TN, TP) and combined indices, based on the amount of pollution produced. Among the BMPs implemented, the 10 m filter strip was most effective in reducing TN load (42.61%), and TP load (39.57%).

Experimental study and simulation of phosphorus purification effects of bioretention systems on urban surface runoff.

Excessive phosphorus (P) contributes to eutrophication by degrading water quality and limiting human use of water resources. Identifying economic and convenient methods to control soluble reactive phosphorus (SRP) pollution in urban runoff is the key point of rainwater management strategies. Through three series of different tests involving influencing factors, continuous operation and intermittent operation, this study explored the purification effects of bioretention tanks under different experimental conditions, it included nine intermittent tests, single field continuous test with three groups of different fillers (Fly ash mixed with sand, Blast furnace slag, and Soil), and eight intermittent tests with single filler (Blast furnace slag mixed with sand). Among the three filler combinations studied, the filler with fly ash mixed with sand achieved the best pollution reduction efficiency. The setting of the submerged zone exerted minimal influence on the P removal of the three filler combinations. An extension of the dry period slightly promoted the P purification effect. The combination of fly ash mixed with sand demonstrated a positive purification effect on SRP during short- or long-term simulated rainfall duration. Blast furnace slag also presented a positive purification effect in the short term, although its continuous purification effect on SRP was poor in the long term. The purification abilities of soil in the short and long terms were weak. Under intermittent operations across different seasons, SRP removal was unstable, and effluent concentration processes were different. The purification effect of the bioretention system on SRP was predicted through partial least squares regression (PLS) modeling analysis. The event mean concentration removal of SRP was positively related to the adsorption capacity of filler and rainfall interval time and negatively related to submerged zones, influent concentration and volume.

Experimental and kinetics study for phytoremediation of sugar mill effluent using water lettuce (Pistia stratiotes L.) and its end use for biogas production.

In present study, the performance of phytoremediation by Pistia stratiotes on sugar mill effluent (SME) and its end use for biogas production are investigated. The objectives of the study are to determine the nutrient and pollution reduction efficiency of P. stratiotes from SME and evaluation of its biomass as a feedstock for biogas production. Various concentrations of SME (25, 50, 75, and 100%) were remediated by Pistia stratiotes (initial weight; 150g) outdoor for 60days under batch mode experimental setup. The results showed that P. stratiotes achieved marked reduction in nutrient (TKN, 72.86%; TP, 71.49%) and pollutant load (EC, 25.69%; TDS, 57.26%; BOD, 69.40%; COD, 61.80%; Ca2+, 56.79%; Mg2+, 55.01%; Na+, 42.86%; K+, 54.38%; MPN, 78.13%; SPC, 60.13%) from 75% SME at the end of the experiment. The highest biomass (328.48±2.04g) and chlorophyll content (3.62±3.04mg/g) were also achieved with 75% SME. The dried biomass of P. stratiotes (from 75% SME) was inoculated with cow dung (10% w/v) and diluted with distilled water (1:10). The whole content was used as a substrate for the biogas production within hydraulic retention time (HRT) of 30days at room temperature. Substrate parameters such as pH, TS (%), COD (mg/L), TKN (%), TOC (%), VS (%), and C/N ratio were reduced from 7.85 to 6.0, 66.65 to 28.65%, 12,900 to 2800mg/L, 0.95 to 0.75%, 45.54 to 19.5%, 76.87 to 28.78%, and 47.94 to 26.00, respectively, in 30days of HRT. About 8478.6mL of cumulative biogas production was evaluated by modified Gompertz equation. Thus, the present investigation not only achieved efficient nutrient and pollution reduction from SME but also proved the potential of P. stratiotes for biogas production.