Developing sustainable, metal-free catalysts for persulfate (PDS) activation is crucial for antibiotic removal in water environments. In this work, boron-sulfur-nitrogen co-doped biochar (BS4C) was synthesized via one-step pyrolysis of walnut shell, boric acid, and thiourea. The introduction of B, N, and S atoms synergistically modulated the electronic structure of carbon, creating abundant electron-deficient sites for PDS activation. As a result, BS4C exhibited excellent catalytic performance toward sulfadiazine (SDZ) degradation, achieving 83.8% removal within 60 min, and maintained strong resistance under the coexistence of various anions and natural organic matter. Radical quenching and EPR analyses confirmed that the process followed a 1O2-dominated non-radical oxidation pathway. These findings highlight the potential of biomass-derived, heteroatom-doped carbon materials as sustainable, metal-free catalysts for antibiotic degradation and water purification.

As a well-known photocatalyst, TiO2 still suffers from rapid electron–hole recombination and limited visible light absorption. To overcome these challenges, the combination of graphene and TiO2 has been proposed. However, traditional methods such as ball milling and hydrothermal synthesis face limitations, including high energy consumption and complex procedures. Here, we develop a simple and industrially feasible method to prepare reduced graphene oxide (rGO)-coated TiO2 nanoparticles, referred to as rGO-TiO2 composites. The optimized rGO-TiO2 composites exhibit an enhanced photocatalytic degradation of rhodamine B (RhB) under simulated sunlight conditions, about 99.95% for 4% rGO-TiO2 within 80 min. The first-order reaction rate constant (k) of 4% rGO-TiO2 (0.0867 min−1) is 5.42 times higher than that of nano TiO2 (0.0135 min−1). The key reactive species involved in the degradation process are identified. Additionally, the effects of pH and NaCl concentration on the degradation efficiency of rGO-TiO2 are also investigated. The 4% rGO-TiO2 composite exhibits an excellent photocatalytic activity within the pH range of 3.87–11.89, and the NaCl concentration does not affect its photocatalytic efficiency. After characterization, the enhanced photocatalytic activity is ascribed to the introduction of rGO and the generation of surface oxygen vacancies (OV) and Ti3+ in TiO2 crystals.

Wastewater treatment makes a non-negligible source of greenhouse gas (GHG) emissions, accounting for one to two percent of global emissions. Up to date, many studies have been undertaken to optimize operations of wastewater treatment plants (WWTPs), however, few have explicitly incorporated GHG emission reductions, and even fewer have real-world applications. This study presented a novel WWTP operation optimization framework that integrates process-based modeling with the genetic algorithm to simultaneously reduce effluent pollutant load, operation costs, and GHG emissions of the WWTPs. The framework was successfully tested at an industry-scaled WWTP located in Eastern China. Seasonal optimization of the WWTP operation in 2017 has revealed greater alignment between reducing greenhouse gas emissions and operating cost, however there was a constant tradeoff between lowering these two targets and reducing effluent pollutant load. Nonetheless, optimized operation strategies were identified that might reduce both the greenhouse gas emissions and operating cost of the WWTP without compromising effluent quality nor exceeding the nation’s sewage discharge standard. Furthermore, the simulation results of 2018 validated the performance of the optimized operation strategies, resulting in considerable reductions in all three targets. The proposed multi-objective WWTP optimization framework is well applicable to WWTPs utilizing different treatment procedures to investigate their potentials for simultaneously reducing effluent pollutant load, operation costs, and GHG emissions.

Due to the advantages of convenient operation and low cost, the use of coagulants is considered a promising method for algae bloom harvesting. However, large dosages, poor algal bloom control rates, and limited phosphorus removal efficiency restrict the usage of most coagulants. In this study, a novel polyaluminum lanthanum silicate (PALS) coagulant was used to remove phosphorus and control algal bloom. The results of isotherm study showed that phosphorus adsorption on PALS fitted Freundlich model, indicating chemisorption and heterogeneous multilayer adsorption were the mechanisms of phosphorus adsorption by PALS. The maximum phosphorus adsorption capacity of PALS by Langmuir model was 485.30 mg/g. According to the algal bloom control experiments, the removal of algae and phosphorus was slight at low dosages of PALS (2 mg/L and 5 mg/L). Shortterm control of the algal bloom was observed within 2 days in PALS-10 group, but the bloom recovered afterward, while phosphorus and algae were almost completely removed in PALS-15 and PALS-20. When the dosage of PALS was <= 10 mg/L, PALS coated the algal cell surfaces and induced mild oxidative stress, showing a little damage to cell integrity. However, the PALS dose over 15 mg/L could effectively capture algal cells through charge neutralization, cause severe oxidative stress, strongly upregulate the expression of selected five genes, significantly damage cell integrity, and lead to algae lysis. These findings demonstrated that PALS is a promising coagulant for phosphorus removal and algal bloom control in eutrophic waters, and the minimum threshold of its usage was 15 mg/L.

Global climate change has led to an increase in both the frequency and magnitude of extreme events around the world, the risk of which is especially imminent in tropical regions. Developing hydrological models with better capabilities to simulate streamflow, especially peak flow, is urgently needed to facilitate water resource planning and management as well as climate change mitigation efforts in the tropics. In view of the need, this paper explores the feasibility of improving streamflow simulation performance in the tropical Kelantan River Basin (KRB) of Peninsular Malaysia through coupling a conceptual process-based hydrological model -Soil and Water Assessment Tool (SWAT) with a deep learning model -Bidirectional Long Short-Term Memory (Bi-LSTM) in two ways. All SWAT parameters were set as their default values in one hybrid model (SWAT-D-LSTM), whereas three most sensitive SWAT parameters were calibrated in the other hybrid model (SWAT-T-LSTM). Comparison of daily streamflow simulation results have shown that SWAT-T-LSTM consistently performs better than SWAT-D-LSTM as well as the stand-alone SWAT and Bi-LSTM model throughout the simulation period. Particularly, SWAT-T-LSTM performs considerably better than the other three models in simulating daily peak flow. Based on the latest projection results of five GCMs from the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6) under three emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5), the best-performed SWAT-T-LSTM was run to assess the potential impacts of climate change on streamflow in the KRB. Ensemble assessment results have concluded that both average and extreme streamflow is much likely to increase considerably in the already wet northeast monsoon season from November to January, which has surely raised the alarm for more frequent flood occurrence in the KRB.

Effective treatment of sewage by wastewater treatment plants (WWTPs) are essential to protecting water environment as well as people's health worldwide. However, operation of WWTPs is usually intricate due to precarious influent characteristics and nonlinear sewage treatment processes. Effective modeling of WWTPs can provide valuable decision-making support to facilitate their daily operations and management. In this study, we have built a novel hybrid model by combining a process-based WWTP model (GPS-X) with a data-driven machine learning model (Random Forest) to improve the simulation of long-term hourly effluent ammonium-nitrogen concentration of a WWTP. Our study results have shown that the hybrid GPS-X-RF model performs the best with a coefficient of determination (R2) of 0.95 and root mean squared error (RMSE) of 0.23 mg/L, followed by the GPS-X model with a R2 of 0.93 and RMSE of 0.33 mg/L and last the Random Forest model with a R2 of 0.84 and RMSE of 0.41 mg/L. Capable of incorporating wastewater treatment mechanisms and utilizing superior data mining capabilities of machine learning, the hybrid model adapts better to the large fluctuations in influent and operating conditions of the WWTP. The proposed hybrid modeling framework may be easily extended to WWTPs of various size and types to simulate their operations under increasingly variable environmental and operating conditions.

In order to address the growing problem of water pollution caused by the excessive discharge of contaminants and provide a better aquatic ecosystem for the public, increasing attention has been paid to the harmlessness and efficiency of coagulation. In this study, polyaluminum lanthanum silicate (PALS) was synthesized through co-polymerization as a novel coagulant to treat wastewater. FTIR, XRD, and SEM were used to analyze the morphology and structure of the material, which further confirmed that the PALS was successfully synthesized. The results indicated that PALS had a great performance in the treatment of a kaolin–humic acid suspension under the optimal synthesis conditions with Al/Si = 3, La/Si = 0.1, and basicity = 0.7. Compared with conventional coagulants, PALS exhibited a better performance at a low coagulant dose and could achieve a good removal effect for an ultraviolet wavelength less than 254 nm (UV254) (83.87%), residual turbidity (0.49 NTU), and dissolved organic carbon (DOC) (69.57%) at the optimal conditions. Additionally, the PALS showed a better effect on phosphate removal than other coagulants did, where the removal efficiency could reach 99.60%. Charge neutralization and adsorption bridging were the potential wastewater treatment mechanisms employed by the PALS, which showed varied contributions under different pH levels. The results indicated that PALS can be a promising coagulant in water treatment.

The outbreak of algae in freshwater bodies poses an important threat to aquatic ecosystems, making finding an effective method for controlling algal blooms imperative. Numerous key factors influence algal bloom outbreaks, with nutrient levels in the water body being the decisive factor. Current research regarding the effect of nutrient levels on algal growth shows that phosphorus is a nutrient that influences algal blooms. Herein, we propose the concept of a modified Monod model for the relationship between algal specific growth rate and phosphorus concentration. Through this improved Monod model, we inferred that the phosphorus concentration at a specific growth rate of zero is the lower threshold of phosphorus concentration that limits algal growth and can effectively control algal outbreaks. This lower threshold is denoted as S′. On the basis of this concept, we designed algal growth experiments. Our results provided an equation that effectively describes the relationship between algal growth and nutrient concentration. When three algal species grow under phosphorus-limited conditions, the corresponding phosphorus concentrations at which they maintain a growth rate of 0 are 0.0565, 0.0386, and 0.0205 mg/L as reflected by the following order of their S′ values: Microcystis wesenbergii S′ < Microcystis aeruginosa S′ < Chlorella vulgaris S′. Furthermore, with the increase in phosphorus concentration, the growth of M. aeruginosa becomes faster than that of M. wesenbergii and C. vulgaris. Consequently, M. aeruginosa becomes the dominant population in the water, leading to its predominance in algal blooms. This situation explains the common occurrence of cyanobacterial blooms. Our findings provide a theoretical basis for regulating the concentration of phosphorus to control algal outbreaks. Therefore, our study is of great importance for controlling the eutrophication of water bodies.

水中天然有机污染物作为致癌消毒副产物的已知前体物,会增强配水系统的生物活性,对人类健康产生严重危害.本研究旨在提高澄清工艺处理水库原水的净化效能,降低中小型水厂出厂水中NOM的含量.试验首先考察了澄清工艺中上升流速对絮体层形成的影响,确定了工艺的最佳上升流速,在此基础上探究了投加粉末活性炭对澄清工艺去除有机物的强化效能.研究结果表明,在3.60 m/h的上升流速下,悬浮泥渣澄清工艺可将原水浊度去除至0.37 NTU,此工况对UV254和CODMn的去除率分别为57.92％和50.53％.在投加粉末活性炭后,工艺对有机物的去除率明显提高,其中在投加量为15.0 mg/L时对UV254和CODMn的去除率分别达到88.69％和63.38％.分子量分级实验结果表明,水库水中小分子量有机物含量最多,其中小于3 kDa的有机物占比59％,经沉淀工艺和澄清工艺处理后,此部分有机物含量分别降低了 30.71％和38.80％,在投加活性炭后沉淀工艺和澄清工艺去除率分别提升了 26.38％和19.07％.三维荧光光谱表明投加粉末活性炭显著提升了对原水中溶解性微生物产物类、芳香族蛋白质Ⅱ类物质的去除效果.

针对上海南汇自来水有限公司惠南水厂和航头水厂受青草沙水库季节性藻类生长影响,出现原水pH值升高导致出厂水铝含量升高的问题,开展了投加二氧化碳调节原水pH值控制余铝的生产性试验.结果 表明:投加二氧化碳调节原水pH值的控铝效果稳定,出厂水铝含量可稳定在0.1 mg/L以内.其中,"气/液"投加装置的二氧化碳利用率为94.3％,二氧化碳投加量为9.02 mg/L,PAC投加量减少了13.1 mg/L;"液/液"投加装置的二氧化碳利用率为92.9％,二氧化碳投加量为8.47 mg/L,PAC投加量减少了17.9 mg/L,有效降低了水厂投加加酸PAC调节原水pH值控铝的运行费用.

稳定的絮体层是决定澄清池工艺效果的关键.国内外对于利用澄清工艺处理原水过程中的絮体层形成机理和净化效果研究十分有限.本文系统研究了表面负荷和絮体层高度分别对澄清柱絮体层形成和处理效果的影响,并进一步分析了絮体层的形成机制.结果 表明,澄清系统相对于传统的沉淀工艺,可有效提高对原水CODMn和藻类的去除率.在表面负荷在2.16～3.60 m/h工况下,澄清系统出水浊度均低于1.0 NTU,计算预测表面负荷大于3.77 m/h和小于1.51 m/h时出水浊度将大于1.0 NTU;表面负荷过低亦会引起出水水质恶化.当絮体层高度小于0.9m,澄清工艺对浊度的处理效果开始出现下降,絮体受到水流剪切力的影响而无法形成稳定的絮体层,出水浊度大于1.0 NTU.

In this research, a novel packed anoxic/oxic moving bed biofilm reactor (MBBR) was established to achieve high-organic matter removal rates, despite the carbon/nitrogen (C/N) ratio of 2.7–5.1 in the influent. Simultaneous nitrification–denitrification (SND) was investigated under a long sludge retention time of 104 days. The system exhibited excellent performance in pollutant removal, with chemical oxygen demand and total nitrogen (TN) enhanced to 93.6–97.4% and 34.4–60%, respectively. Under low C/N conditions, the nitrogen removal process of A/O MBBR system was mainly achieved by anaerobic denitrification. The increase of C/N ratio enhanced SND rate of the aerobic section, where dissolved oxygen was maintained at the range of 4–6 mg/L, and resulted in higher TN removal efficiency. The microbial composition and structures were analyzed utilizing the MiSeq Illumina sequencing technique. High-throughput pyrosequencing results indicated that the dominant microorganisms were Proteobacteria and Bacteroidetes at the phylum level, which contributes to the removal of organics matters. In the aerobic section, abundances of Nitrospirae (1.12–29.33%), Burkholderiales (2.15–21.38%), and Sphingobacteriales (2.92–11.67%) rose with increasing C/N ratio in the influent, this proved that SND did occur in the aerobic zone. As the C/N ratio of influent increased, the SND phenomenon in the aerobic zone of the system is the main mechanism for greatly improving the removal rate of TN in the aerobic section. The C/N ratio in the aerobic zone is not required to be high to exhibit good TN removal performance. When C/NH4+ and C/TN in the aerobic zone were higher than 2.29 and 1.77, respectively, TN removal efficiency was higher than 60%, which means that carbon sources added to the reactor could be saved. This study would be vital for a better understanding of microbial structures within a packed A/O MBBR and the development of cost-efficient strategies for the treatment of low C/N wastewater.

This study investigates the morphological changes in cyanobacterial and microbial distribution characteristics of surface sediments, throughout different cyanobacterial blooms periods in Zhushan Bay, Taihu Lake. Comparative microscopic analysis of cyanobacterial morphology (n = 36) was performed during the formation period (W-1), stationary period (W-2), decline period (W-3) and decomposition period (W-4). Simultaneously, sequence analysis was performed on microbial 16S rRNA genes in sediments (n = 36) by high-throughput sequencing. The coverage of the sequencing library was very high (100%) indicating that the sequencing results well represented the microbes present in samples, among which the species richness in W-4 was the highest, while the species distribution uniformity was low. The microbial abundance distribution in all four periods showed that Firmicutes (33.45%), Cyanobacteria (30.44%), Proteobacteria (27.17%) and Bacteroidetes (7.2%) were the dominant flora, with W-1 dominated by Cyanobacteria, W-2 dominated by Firmicutes, W-3 dominated by Proteobacteria and Cyanobacteria, and W-4 dominated by Proteobacteria. There were significant differences in microbial species abundance and distribution observed during each cyanobacterial bloom period and synchronous microorganisms in the sediment regulated bacterial abundance and distribution through signal transduction of various proteases. The findings of this study help to establish the impact of cyanobacteria blooms on the sediment environment and benefit the comprehensive assessment of hazard presented by cyanobacteria to the aquatic environment.

Cyanobacterial blooms pose a serious threat to aquatic environmental health and have emerged as a primary issue in the recovery of eutrophic lakes. In order to comprehensively establish the effects of cyanobacterial blooms on nutrients in the aquatic environment, nutrient migration and transformation were studied in freshwater and sediments during cyanobacterial bloom decomposition. Cyanobacteria and sediments were collected from Zhushan Bay, in Taihu Lake, and the process of cyanobacterial decomposition was simulated in the laboratory. The focus of this research was to assess the effects of cyanobacterial decomposition on physicochemical parameters and nutrient concentrations in water, the vertical distribution of nutrients in sediments. We also determined the moisture content (ΔCw) and organic matter content (ΔOM) in surface sediments. Correlations were assessed between cyanobacterial decomposition and nutrient concentrations in water, with ΔCw and ΔOM in surface sediments simultaneously analyzed. In the water column, electric conductivity (Ec) was found to significantly increase, while dissolved oxygen (DO) and oxidation reduction potential (ORP) rapidly reduced. In addition, pH initially decreased and then increased, while ultraviolet light (UV254) exhibited an opposite trend, which was related to the release and degradation of organic matter during the decomposition of cyanobacteria. Other nutrient concentrations were found to increase gradually with time, with the exception of nitrate nitrogen (NO3−–N), indicating that nutrients undergo temporal transitions between forms during cyanobacterial decomposition. Cyanobacterial decomposition causes ΔOM and ΔCw to increase in surface sediment layers, affecting the vertical distribution of nutrient species in the sediment. The water-sediment interface nutrient flux intensity was ranked in the order total nitrogen (TN) > ammonia nitrogen (NH4+–N) > NO3−–N > total phosphorus (TP), which was related to the settlement of cyanobacterial debris during cyanobacterial decomposition. Good binomial relationships (R2 > 0.90, p < 0.05) were found between cyanobacterial density and nutrient concentrations in the waterbody, as well as between cyanobacterial density and ΔOM or ΔCw in the surface sediment. Cyanobacterial decomposition affected various water quality parameters, leading to nutrient migration and transformation in the water-sediment interface, providing nutrients to drive cyanobacterial bloom development.

To investigate the deleterious ecological effects of cyanobacteria on submerged macrophytes, this study investigated the effects of different concentrations of fresh cyanobacteria (FC) and cyanobacteria decomposition solution (CDS) on an experimental group of submerged macrophytes (Vallisneria natans (Lour.) Hara and Myriophyllum verticillatum Linn.). The results showed that FC and CDS not only lead to decrease in biomass and significant changes in enzyme activity and chlorophyll content in tissue, but also affected the permeability of cell membranes. The extent of damage was in the order CDS > FC, and the comprehensive stress resistance of Vallisneria natans (2.994) was more than that of Myriophyllum verticillatum (2.895). In addition, semi-permeable membranes can reduce plant damage by FC and CDS, but cannot completely prevent it. FC and CDS mainly affected the relative distribution of microbial genera on the surface of aquatic plants (p < 0.05). Furthermore, CDS caused irreversible damage to plant cells and induced programmed cell death (PCD) of plants to accelerate their decline. Therefore, FC and CDS may be one of the main reasons for the decline in submerged vegetation. This study provides a scientific basis for evaluating the harmful effects of cyanobacteria on submerged macrophytes.

Phthalate esters (PAEs) are widely used industrial raw materials that are well known for their environmental contamination and toxicological effects as "endocrine disruptors." In this study, environmental levels of PAEs and eco-toxicological risk assessments were determined in the eight estuaries of the Pearl River (Estuaries), main upstream tributary (Xijiang River), urban river network (River network), and nature reserve reservoir (Reservoirs). Water and sediment samples from the above water systems were collected during the low-water period (May) and the high-water period (August) between 2012 and 2014. Solid phase and ultrasonic methods were used to extract 14 different PAEs that were analyzed by gas chromatography. The analytical average recovery of PAEs in water and sediment was 75.4% ± 4.9% and 121.5% ± 8.9%, respectively. The results showed that PAEs were detected in all of the samples, and the di-n-butyl phtalate (DBP) and benzyl butyl phthalate (BBP) monomers had a detection rate of 100% in water. Similarly, in sediment samples, the detection rates of diisobutyl phthalate (DiBP), DBP, dimethoxyethyl phthalate (DMEP), BBP, di-n-octyl phthalate (DnOP), and DNP ranged from 66.7 to 100%. Among these, in sediment samples, di(2-ethylhexyl) phthalate (DEHP) and phthalic acid bis(2-butoxyethyl) ester (DBEP) had detection rates of 95.8% to 100% in the Estuaries, Xijiang River, and River network. The concentrations of Σ14PAEs in water samples and sediments ranged from 12.95 ± 1.97 to 6717.29 ± 112.37 ng/L and 71.99 ± 8.72 to 17,340.04 ± 227.83 ng/g-dw, respectively. During the low-water period, the average concentration of Σ14PAEs in water and sediment was 1159.58 ± 97.22 ng/L and 2842.50 ± 178.21 ng/g-dw, respectively, and during the high-water period, 822.83 ± 53.19 ng/L and 1936.42 ± 111.31 ng/g-dw, respectively. In water, the average concentration of Σ14PAEs in 2013 and 2014 was 963.39 ± 19.55 ng/L and 2815.35 ± 176.32 ng/L, respectively. In sediment, the average concentrations of Σ14PAEs in 2012 to 2014 were 990.10 ± 23.33 ng/g-dw, 1084.20 ± 112.12 ng/g-dw, and 1816.89 ± 79.97 ng/g-dw, respectively, with concentrations showing an increasing trend year after year (2014 > 2013 > 2012). Potential risk assessment of water ecological, the results show that exceeding environmental risk level (ERL) value in higher molecular weight plasticizer (DEHP, DMEP, DNOP, DNP) was mainly distributed in water, the lower molecular weight plasticizer (BMP, DiBP) was mainly distributed in sediment.

Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn-5(OH)(8)Cl-2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 mu m, respectively.

The use of aquatic plants has recently become a popular technique for ecological restoration and purification of eutrophic rivers and lakes. In this paper, various technologies were studied and designed against the background of research and demonstration projects for pollution control in Dianchi Lake and comprehensive improvement of water quality. Different technical units were designed in the horizontal and vertical spaces of the water body. Horizontal spaces included plant buffers on the surface, algae enrichment and diversion, innovative floating beds, and emerging plant zones at the shoreline. Vertical spaces include ecological floating beds, ecological jellyfish, and ecological membrane coverings. Spatial growth patterns of aquatic plants were constructed with rational use of water space and integration with various techniques to maximize the absorption of nutrients in the lake, increase the transparency of the water, and alleviate lake eutrophication. The previous technologies were combined, and technical demonstrations were conducted using experiments. We set up an integrated technical demonstration district with an area of 0.25 km2 on the north shore of Dianchi Lake, and the results demonstrated the following: water transparency increased by >50 cm; algae biomass decreased by >70%; and the percent removal of total phosphorous (TP), total nitrogen (TN), and chemical oxygen demand (CODMn) was >30%.

Given the high ammonia nitrogen (NH3-N) concentration and low biological oxygen demand/chemical oxygen demand (BOD/COD) ratio (<0.1) in mature landfill leachate, it is hard to treat it with the membrane bioreactor (MBR) system to meet the discharge standard for Pollution Control of the Municipal Solid Waste Landfills" (GB16889-2008) without additional carbon source. This pilot-scale study evaluated the use of negative pressure steam-stripping technology for the pretreatment of mature landfill leachate. Our study results have shown that NH3-N concentrations of raw leachate and treated effluent from steam-stripping tower were respectively 2941-3648 mg/L and 401-710 mg/L, yielding an average NH3-N removal efficiency of 82.03%. Nitrogen (N) was recovered via the formation of NH4HCO3 in the ammonia recovery tower, and the effluent of steam-stripping tower was further treated by MBR system. Economic evaluation results showed that initial investment in pretreatment could be offset by respectively reducing energy consumption and operational costs of the MBR system by 60% and 80%. Furthermore, most of Ca2+ and mg(2+) in mature leachate was removed through the formation of CaCO3 and MgCO3 after pretreatment, which avoided membrane fouling and increased the membrane filtration efficiency of MBR system. To conclude, this pilot-study has indicated that negative pressure steam-stripping pretreatment is an efficient and cost-effective technology for the removal of NH3-N, making MBR technology viable without the need for additional carbon source. (C) 2018 Elsevier Ltd. All rights reserved.

The biological slow filtration (BSF) system as a simple and efficient environmental technology has been widely applied in treatment of ‘micro-polluted’ water. At present, many related studies have focused on the removal efficiency of biological indicators (such as bacteria and viruses). However, there is less research on the removal performance of nutrients and organics in the BSF system. In this paper, we employed a lab-scale biological slow filter to study the removal efficiency and degradation mechanism of nutrients and organics. We proved through adsorption of filter layer at the early running stage and biodegradation at the later stage, the BSF system could achieve effective removal of NH3-N, TN, TP, CODMn and turbidity and the corresponding removal rates are 83.65%, 42.45%, 42.94%, 60.41% and 83.55%, respectively. Furthermore, we also explored the influence of four main factors (filtration rate, filter depth, hydraulic head and temperature) and their interactions on removal rates of nutrients and organics in the BSF system and obtained the optimal operating parameters as follows: filtration rate 0.1 m/h, filter depth 0.8 m, hydraulic head 0.64 m, temperature 26.06 °C. This study would provide a theoretical foundation for the actual application of biological slow filter in treatment of micro-polluted water in developing countries and offer an optimized basis for the design of operating conditions.