A bioretention unit (BRU) or cell is a green infrastructure practice that is widely used as a low impact development (LID) technique for urban stormwater management. Bioretention is considered a good fit for use in China’s sponge city construction projects. However, studies on bioretention design, which incorporates site-specific environmental and social-economic conditions in China are still very much needed. In this study, an experimental BRU, consisted of two cells planted with Turf grass and Buxus sinica,was tested with eighteen synthesized storm events. Three levels (high, median, low) of flows and concentrations of pollutants (TN, TP and COD) were fed to the BRU and the performance of which was examined. The results showed that the BRU not only delayed and lowered the peak flows but also removed TN, TP and COD in various ways and to different extents. Under the high, medium and low inflow rate conditions, the outflow peaks were delayed for at least 13 minutes and lowered at least 52%. The two cells stored a maximum of 231 mm and 265 mm for turf grass and Buxus sinica, respectively. For both cells the total depth available for storage was 1,220 mm, including a maximum 110 mm deep ponding area. The largest infiltrate rate was 206 mm/h for both cells with different plants. For the eighteen events, TP and COD were removed at least 60% and 42% by mean concentration, and 65% and 49% by total load, respectively. In the reservoir layer, the efficiency ratio of removal of TN, TP and COD were 52%, 8% and 38%, respectively, within 5 days after runoff events stopped. Furthermore, the engineering implication of the hydrological and water quality performances in sponge city construction projects is discussed.
This paper presents an investigation of the feasibility of recycling silicon carbide waste (SCW) as a source of mixture materials in the production of cement mortar. Mortars with SCW were prepared by replacing different amounts of cement with SCW, and the properties of the resulting mortars, such as the fluidity, strength and shrinkage, were studied in this work. Thermogravimetry-differential scanning calorimetry and scanning electron microscopy were employed to understand the reasons for the property changes of the mortars. The results indicate that SCW decreases the initial and 1-h fluidity of fresh mortar but improves the loss of fluidity. The mortar with SCWexhibits a lower strength at 3 d and 7 d but a higher strength at 28 d and 56 d compared to the control. The shrinkage rate of cement mortar with SCW shows an obvious decrease as the replacement ratio increases. In addition, the content of calcium hydroxide in hardened paste also shows that SCW has some impact on the hydration of the cement-SCW system. The microstructures of the hardened paste also show evidence for a later strength change of mortar containing SCW. This work provides a strategic reference for possibly applying SCW as a mixture material in the production of cement mortar.
Mercury enrichment in response to elevated atmospheric mercury concentrations in the organs of rape (Brassica napus) was investigated using an open top chamber fumigation experiment and a soil mercury enriched cultivation experiment. Results indicate that the mercury concentration in leaves and stems showed a significant variation under different concentrations of mercury in atmospheric and soil experiments while the concentration of mercury in roots, seeds and seed coats showed no significant variation under different atmospheric mercury concentrations. Using the function relation established by the experiment, results for atmospheric mercury sources in rape field biomass showed that atmospheric sources accounted for at least 81.81%of mercury in rape leaves and 32.29% of mercury in the stems. Therefore, mercury in the aboveground biomass predominantly derives from the absorption of atmospheric mercury.
Sulfamethoxzole (SMX) and trimethoprim (TMP), two combined-using sulfonamide antibiotics, have gained increasing attention in the surface water, groundwater and the drinking water because of the ecological risk. The removal of TMP and SMX by artificial composite soil treatment system (ACST) with different infiltration rates was systematically investigated using K+, Na+, Ca2+, Mg2+ hydrogeochemical indexes. Batch experiments showed that the sorption onto the low-cost and commercially available clay ceramsites was effective for the removal of SMX and TMP from water. The column with more silty clay at high infiltration rate (1.394 m·d–1) had removal rates of 80% to 90% for TMP and 60% to 70% for SMX. High SMX and TMP removal rates had a higher effluent concentration of K+, Ca2+ and Mg2+ and had a lower effluent Na+ concentration. Removal was strongly related to sorption. The results showed that the removal of SMX and TMP was related to hydrogeochemical processes. In this study, ACST is determined to be applicable to the drinking water plants.
Benzotriazole (BTA) is an emerging contaminant that also is a recalcitrant compound. Sequential and intimate coupling of UV-photolysis with biodegradation were investigated for their impacts on BTA removal and mineralization in aerobic batch experiments. Special attention was given to the role of its main photolytic products, which were aminophenol (AP), formic acid (FA), maleic acid (MA), and phenazine (PHZ). Experiments with sequential coupling showed that BTA biodegradation was accelerated by photolytic pretreatment up to 9 min, but BTA biodegradation was slowed with longer photolysis. FA and MA accelerated BTA biodegradation by being labile electron-donor substrates, but AP and PHZ slowed the rate because of inhibition due to their competition for intracellular electron donor. Because more AP and PHZ accumulated with increasing photolysis time, their inhibitory effects began to dominate with longer photolysis time. Intimately coupling photolysis with biodegradation relieved the inhibition effect, because AP and PHZ were quickly biodegraded and did not accumulate, which accentuated the beneficial effect of FA and MA.
The objective of this study was to provide insight into human exposure to trace contaminants bearing red mud, derived precipitates and geopolymeric blocks due to inhalation contact and/or hand-to-mouth ingestion. The in vitro bioaccessibility behavior of trace contaminants was investigated with the PBET (physiologically based extraction test), ALF (artificial lysosomal fluid) and MGS (modified Gamble’ solution) methods. The results showed that total contents of trace contaminants and operation parameters, such as pH and chelating properties of simulated gastrointestinal phases (PBET), played a joint role in controlling the bioaccessibility efficacy for size-fractionated red mud particles. As for airborne particles (<38 μm size fractions), trace contaminants concentrations extracted by MGS was significantly higher than those by ALF. Additionally, higher bioaccessibility (PBET) values of Cu, Pb, Zn, As, V and U were obtained from red mud derived precipitates compared with those of red mud itself. Even though short-term and long-term leaching values of trace contaminants were relatively lower in the prepared geopolymeric blocks, the health risk could be significantly higher due to the more pronounced bioaccessibility characteristics.
Effect of different carbon sources on purification performance and change of microbial community structure in a novel A2N-MBR process were investigated. The results showed that when fed with acetate, propionate or acetate and propionate mixed (1:1) as carbon sources, the effluent COD, NH4+-N, TN and TP were lower than 30, 5, 15 and 0.5 mg?L–1, respectively. However, taken glucose as carbon source, the TP concentration of effluent reached 2.6 mg?L–1. Process analysis found that the amount of anaerobic phosphorus release would be the key factor to determine the above effectiveness. The acetate was beneficial to the growth of Candidatus Accumulibacter associated with biological phosphorus removal, which was the main cause of high efficiency phosphorus removal in this system. In addition, it could eliminate the Candidatus Competibacter associated with glycogen-accumulating organisms and guarantee high efficiency phosphorus uptake of phosphorus accumulating organisms in the system with acetate as carbon source.
The quantification and effects of system pH value on the interactions between Pb(II) and the biopolymer in activated sludge were investigated. The biopolymer had two protein-like fluorescence peaks (Ex/Em = 280 nm/326–338 nm for peak A; Ex/Em = 220–230 nm/324–338 nm for peak B). The fluorescence intensities of peak B were higher than those of peak A. The fluorophores of both peaks could be largely quenched by Pb(II), and the quencher dose for peak B was about half of that for peak A. The modified Stern-Volmer equation well depicted the fluorescence quenching titration. The quenching constant (Ka) values for both peaks decreased with rising system pH value, and then sharply decreased under alkaline conditions. It could be attributed to that the alkaline conditions caused the reduction of available Pb(II) due to the occurrence of Pb(OH)2 sediments. The Ka values of peak B were bigger than those for peak A at the same system pH values. Accordingly, the aromatic proteins (peak B) played a key role in the interactions between metal ions and the biopolymer.
The diffusion of municipal wastewater treatment technology is vital for urban environment in developing countries. China has built more than 3000 municipal wastewater treatment plants in the past three decades, which is a good chance to understand how technologies diffused in reality.We used a data-driven approach to explore the relationship between the diffusion of wastewater treatment technologies and collaborations between organizations. A database of 3136 municipal wastewater treatment plants and 4634 collaborating organizations was built and transformed into networks for analysis. We have found that: 1) the diffusion networks are assortative, and the patterns of diffusion vary across technologies; while the collaboration networks are fragmented, and have an assortativity around zero since the 2000s. 2) Important projects in technology diffusion usually involve central organizations in collaboration networks, but organizations become more central in collaboration by doing circumstantial projects in diffusion. 3) The importance of projects in diffusion can be predicted with a Random Forest model at a good accuracy and precision level. Our findings provide a quantitative understanding of the technology diffusion processes, which could be used for waterrelevant policy-making and business decisions.
With the increasing concern about the serious global energy crisis and high energy consumption during high content solid wastes (HCSWs) treatment, microbial fuel cell (MFC) has been recognized as a promising resource utilization approach for HCSW stabilization with simultaneous electrical energy recovery. In contrast to the conventional HCSW stabilization processes, MFC has its unique advantages such as direct bio-energy conversion in a single step and mild reaction conditions (viz., ambient temperature, normal pressure, and neutral pH). This review mainly introduces some important aspects of electricity generation from HCSWand its stabilization in MFC, focusing on: (1) MFCs with different fundamentals and configurations designed and constructed to produce electricity from HCSW; (2) performance of wastes degradation and electricity generation; (3) prospect and deficiency posed by MFCs with HCSWas substrates. To date, the major drawback of MFCs fueled by HCSW is the lower power output than those using simple substrates. HCSW hydrolysis and decomposition would be a major tool to improve the performance of MFCs. The optimization of parameters is needed to push the progress of MFCs with HCSW as fuel.
The toxic and recalcitrant polychlorinated biphenyls (PCBs) adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs (70 mmol·L–1) and lactate (10 mmol·L–1), the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively (all in moL ratio). This dechlorination process led to tetra-CBs (46.4%) as the predominant dechlorination products, followed by penta-(22.1%) and tri-CBs (5.4%). The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 ×105±0.5 × 105 to 4.99 × 107±0.32 × 107 copies mL–1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is prior to be applied for in situ bioremediation of notorious halogenated compounds.
Conventional biological removal of nitrogen and phosphorus is usually limited due to the lack of biodegradable carbon source, therefore, new methods are needed. In this study, a new alternative consisting of enhanced biological phosphorus removal (EBPR) followed by partial nitritationanammox (PN/A), is proposed to enhance nutrients removal from municipal wastewater. Research was carried out in a laboratory-scale system of combined two sequencing batch reactors (SBRs). In SBR1, phosphorus removal was achieved under an alternating anaerobic-aerobic condition and ammonium concentration stayed the same since nitrifiers were washed out from the reactor under short sludge retention time of 2–3 d. The remaining ammonium was further treated in SBR2 where PN/A was established by inoculation. A maximum of nitrogen removal rate of 0.12 kg N?m–3?d–1 was finally achieved. During the stable period, effluent concentrations of total phosphorus and total nitrogen were 0.25 and 10.8 mg?L–1, respectively. This study suggests EBPR-PN/A process is feasible to enhance nutrients removal from municipal wastewater of low influent carbon source.
A novel, functionalized bubble surface can be obtained in dissolved air flotation (DAF) by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter (NOM) removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the DAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for DAF to enhance NOM removal.
As the Electrical and Electronic Equipment (EEE) are upgraded more frequently in China, a large quantity of Waste Electrical and Electronic Equipment (WEEE) was and will be generated. It becomes an urgent issue to develop and adopt an effective End-of-Life (EoL) strategy for EEE in order to balance the resource recovery and environmental impacts. In an EoL strategy hierarchy for EEE, reuse strategy is usually deemed to be prior to materials recovery and other strategies. But in practice, the advantages and disadvantages of different strategies are always context-dependent. Therefore, main EoL strategies for EEE in China need to be evaluated in environment and resources aspects from the life cycle perspective. In this study, the obsolete refrigerator and Power Supply Unit (PSU) of desktop PC are both taken as the target products. Life Cycle Assessment (LCA) is applied to assess the environmental impacts of different EoL scenarios in China: Unit Reuse Scenario (URS), Component Reuse Scenario (CRS) and Materials Recovery Scenario (MRS). The LCA results show that the EoL strategies hierarchy is reasonable for the part of computer, but not necessarily suitable for obsolete refrigerators. When the policy makers promote or demote one EoL strategy especially reuse, it is necessary to take subsequent impacts into consideration.
The considerable compounds content, abundance, and low costs involved has led to the proposal to use sewage sludge as raw material for biodiesel production. The transesterification reaction is catalyzed using an acid catalyst instead of base catalysts because of the high free fatty acid concentration. However, the use of a base catalyst, particularly a solid base catalyst, has certain advantages, including faster reaction speed and easier separation. In this study, we utilize in situ transesterification by base catalyst (KOH, KOH/activated carbon (AC) and KOH/CaO) with sewage sludge as raw material. Many conditions have been tested to increase biodiesel yield through single-factor tests, including mass fraction and catalyst dosage. Preliminary experiments have optimized reaction time and temperature. However, the three catalysts did not work better than H2SO4, which had a maximum yield of 4.6% (dry sewage sludge base) considering the purity by KOH, KOH/CaO, and KOH/AC. The features of the catalyst were analyzed using XRD, BETand SEM. As to BETof KOH/AC and the good spiculate formation of KOH crystal appears to be essential to its function. As for KOH/CaO, the formation of K2O and absorption points is likely essential.
Exploration of heavy metals and organic pollutants, their leaching capacity along with health and environmental risks in contaminated industrial construction and demolition waste (ICDW) within a pesticide manufacturing plant were investigated. A maximum content of 90.8 mg?kg–1 Cd was found present in the wastes, which might originate from phosphorus rocks and industrial sulfuric acid used in pesticide production processes. An average concentration of 979.8 mg?kg–1 dichlorovos and other 11 organophosphorus pesticide were also detected. Relatively high leaching rates of around 4.14‰were obtained from laboratory simulated ICDW using both glacial acetic acid-sodium hydroxide and deionized water. Pesticide pollutants had the strongest tendency to retaining on dry bricks (leaching rate 1.68‰) compared to mortar-coatings, etc. due to their different physical characteristics and octanol-water partioning coefficient. Mobility of pesticide from on-site ICDW by water was spatially correlated to waste types, process sections and human activities, with a flux of leaching rate between 5.9‰ to 27.4%. Risk-based corrective action (RBCA) model was used to simulate the risk of contaminated ICDW debris randomly scattered. Oral and dermal ingestion amount by local workers was 9.8 × 10–3 and 1.9 × 10–2 mg?(kg?d)–1, respectively. Potential leaching risk to aquatic systems exceeded the limit for nearly 75% waste. Environmental and health risk exceedance was found in most ICDW, while the risk value of the most severely contaminated brick waste was 660 times beyond critical level. Implications for waste management involving construction and deconstruction work, waste transferring and regulation supplying were also provided.
The gene for the catalytic domain of thermostable endo-β-1,3-glucanase (laminarinase) LamA was cloned from Thermotoga maritima MSB8 and heterologously expressed in a bioengineered Synechococcus sp. PCC 7002. The mutant strain was cultured in a photobioreactor to assess biomass yield, recombinant laminarinase activity, and CO2 uptake. The maximum enzyme activity was observed at a pH of 8.0 and a temperature of 70°C. At a CO2 concentration of 5%, we obtained a maximum specific growth rate of 0.083 h–1, a biomass productivity of 0.42 g?L–1?d–1, a biomass concentration of 3.697 g?L–1, and a specific enzyme activity of the mutant strain of 4.325 U?mg–1 dry mass. All parameters decreased as CO2 concentration increased from 5% to 10% and further to 15% CO2, except enzyme activity, which increased from 5% to 10% CO2. However, the mutant culture still grew at 15% CO2 concentration, as reflected by the biomass productivity (0.26 g?L–1?d–1), biomass concentration (2.416 g?L–1), and specific enzyme activity (3.247 U?mg–1 dry mass).
Catalytic pyrolysis of thermoplastics extracted from waste electrical and electronic equipment (WEEE) was investigated using various fly ash-derived catalysts. The catalysts were prepared from fly ash by a simple method that basically includes a mechanical treatment followed by an acid or a basic activation. The synthesized catalysts were characterized using various analytical techniques. The results showed that not treated fly ash (FA) is characterized by good crystallinity, which in turn is lowered by mechanical and chemical treatment (fly ash after mechanical and acid activation, FAMA) and suppressed almost entirely down to let fly ash become completely amorphous (fly ash after mechanical and basic activation FAMB). Simultaneously, the surface area resulted increased. Subsequently, FA, FAMB and FAMA were used in the pyrolysis of a WEEE plastic sample at 400°C and their performance were compared with thermal pyrolysis at the same temperature. The catalysts principally improve the light oil yield: from 59 wt.% with thermal pyrolysis to 83 wt.% using FAMB. The formation of styrene in the oil is also increased: from 243 mg/g with thermal pyrolysis to 453 mg/g using FAMB. As a result, FAMB proved to be the best catalyst, thus producing also the lowest and the highest amount of char and gas, respectively.
The effect of microwave pretreatment on the anaerobic degradation of hyacinth was investigated using response surface methodology (RSM). The components of lignin and the other constituents of hyacinth were altered by microwave pretreatment. Comparison of the near-infrared spectra of hyacinth pretreated by microwave irradiation and water-heating pretreatment revealed that no new compounds were generated during hyacinth pretreatment by microwave irradiation. Atomic force microscopy observations indicated that the physical structures of hyacinth were disrupted by microwave pretreatment. The yield of methane per gram of the microwave-irradiated substrate increased by 38.3% as compared to that of the substrate pretreated via water-heating. A maximum methane yield of 221 mL?g-sub–1 was obtained under the optimum pretreatment conditions (substrate concentration (PSC) = 20.1 g?L–1 and pretreatment time (PT) = 14.6 min) using RSM analysis. A maximum methane production rate of 0.76 mL?h–1?g-sub–1 was obtained by applying PSC = 9.5 g?L–1 and PT = 11 min. Interactive item coefficient analysis showed that methane production was dependent on the PSC and PT, separately, whereas the interactive effect of the PSC and PT on methane production was not significant. The same trend was also observed for the methane production rate.
Aromatics-contaminated soil is of particular environmental concern as it exhibits carcinogenic and mutagenic properties. Bioremediation, a biological approach for the removal of soil contaminants, has several advantages over traditional soil remediation methodologies including high efficiency, complete pollutant removal, low expense and limited or no secondary pollution. Bioaugmentation, defined as the introduction of specific competent strains or consortia of microorganisms, is a widely applied bioremediation technology for soil remediation. In this review, it is concluded which several successful studies of bioaugmentation of aromatics-contaminated soil by single strains or mixed consortia. In recent decades, a number of reports have been published on the metabolic machinery of aromatics degradation by microorganisms and their capacity to adapt to aromatics-contaminated environments. Thus, microorganisms are major players in site remediation. The bioremediation/bioaugmentation process relies on the immense metabolic capacities of microbes for transformation of aromatic pollutants into essentially harmless or, at least, less toxic compounds. Aromatics-contaminated soils are successfully remediated with adding not only single strains but also bacterial or fungal consortia. Furthermore several novel approaches, which microbes combined with physical, chemical or biological factors, increase remediation efficiency of aromatics-contaminated soil. Meanwhile, the environmental factors also have appreciable impacts on the bioaugmentation process. The biostatistics method is recommended for analysis of the effects of bioaugmentation treatments.
