Cover illustration
In the paper concepts for wastewater treatment of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for Nremoval in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e.de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow di [Detail] ...
Without considering the ecosystem-dependence of agricultural production, irrational use of agricultural technologies could bring only short-term economic benefits but leave long-term environmental deterioration. If some agricultural lands have to be abandoned because of these technologies such as chemical films or groundwater depletion, it will aggravate the burden of remaining lands for maintaining or enhancing production. Thus, agricultural production should be a part of public services, requiring the consideration of interests of different stakeholders and sustainability.
Continuous pulsed plate bioreactor (PPBR) was used for phenol biodegradation.
Pseudomonas desmolyticum cells immobilized on granular activated carbon was used.
Dynamic and steady state biofilm characteristics depend on dilution rate (DR).
Lower DR favour phenol degradation and uniform, thick biofilm formation.
Exo polymeric substance production in biofilm are favoured at lower dilution rates.
Pulsed plate bioreactor (PPBR) is a biofilm reactor which has been proven to be very efficient in phenol biodegradation. The present paper reports the studies on the effect of dilution rate on the physical, chemical and morphological characteristics of biofilms formed by the cells of Pseudomonas desmolyticum on granular activated carbon (GAC) in PPBR during biodegradation of phenol. The percentage degradation of phenol decreased from 99% to 73% with an increase in dilution rate from 0.33 h?1 to 0.99 h?1 showing that residence time in the reactor governs the phenol removal efficiency rather than the external mass transfer limitations. Lower dilution rates favor higher production of biomass, extracellular polymeric substances (EPS) as well as the protein, carbohydrate and humic substances content of EPS. Increase in dilution rate leads to decrease in biofilm thickness, biofilm dry density, and attached dry biomass, transforming the biofilm from dense, smooth compact structure to a rough and patchy structure. Thus, the performance of PPBR in terms of dynamic and steady-state biofilm characteristics associated with phenol biodegradation is a strong function of dilution rate. Operation of PPBR at lower dilution rates is recommended for continuous biologic treatment of wastewaters for phenol removal.
A bio-electrochemical fuel cell reactor with cathodic Fe0/TiO2 generates electricity.
It destroys recalcitrant pollutants in cathode chamber without photocatalysis.
Fe0/TiO2 generates reactive oxygenated species in the dark or under photocatalysis.
Cathodic produced ROS (hydroxy radical/superoxide radical) can degrade tetracycline or dyes.
Electricity generation is enhanced by semiconductor catalyzed cathodic degradation of pollutants.
In this study, a new water treatment system that couples (photo-) electrochemical catalysis (PEC or EC) in a microbial fuel cell (MFC) was configured using a stainless-steel (SS) cathode coated with Fe0/TiO2. We examined the destruction of methylene blue (MB) and tetracycline. Fe0/TiO2 was prepared using a chemical reduction-deposition method and coated onto an SS wire mesh (500 mesh) using a sol technique. The anode generates electricity using microbes (bio-anode). Connected via wire and ohmic resistance, the system requires a short reaction time and operates at a low cost by effectively removing 94% MB (initial concentration 20 mg·L−1) and 83% TOC/TOC0 under visible light illumination (50 W; 1.99 mW·cm−2 for 120 min, MFC-PEC). The removal was similar even without light irradiation (MFC-EC). The EEo of the MFC-PEC system was approximately 0.675 kWh·m−3·order−1, whereas that of the MFC-EC system was zero. The system was able to remove 70% COD in tetracycline solution (initial tetracycline concentration 100 mg·L−1) after 120 min of visible light illumination; without light, the removal was 15% lower. The destruction of MB and tetracycline in both traditional photocatalysis and photoelectrocatalysis systems was notably low. The electron spin-resonance spectroscopy (ESR) study demonstrated that ·OH was formed under visible light, and ·O2− was formed without light. The bio-electricity-activated O2 and ROS (reactive oxidizing species) generation by Fe0/TiO2 effectively degraded the pollutants. This cathodic degradation improved the electricity generation by accepting and consuming more electrons from the bio-anode.
Syntrophic propionate-oxidizing microflora B83 was enriched from anaerobic sludge.
The bioaugmentation of microflora B83 were evaluated from wastewater treatment.
Methane yield and COD removal were enhanced by bioaugmentation of microflora B83.
Hydrogen-producing acetogensis was a rate-limiting step in methane fermentation.
Methane fermentation process can be restricted and even destroyed by the accumulation of propionate because it is the most difficult to be anaerobically oxidized among the volatile fatty acids produced by acetogenesis. To enhance anaerobic wastewater treatment process for methane production and COD removal, a syntrophic propionate-oxidizing microflora B83 was obtained from an anaerobic activated sludge by enrichment with propionate. The inoculation of microflora B83, with a 1:9 ratio of bacteria number to that of the activated sludge, could enhance the methane production from glucose by 2.5 times. With the same inoculation dosage of the microflora B83, COD removal in organic wastewater treatment process was improved from 75.6% to 86.6%, while the specific methane production by COD removal was increased by 2.7 times. Hydrogen-producing acetogenesis appeared to be a rate-limiting step in methane fermentation, and the enhancement of hydrogen-producing acetogens in the anaerobic wastewater treatment process had improved not only the hydrogen-producing acetogenesis but also the acidogenesis and methanogenesis.
pH values of the BSA solution significantly impact the process of membrane fouling.
Dramatic flux decline is caused by membrane–BSA adhesion force at start of filtration.
XDLVO theory shows the polar or Lewis acid–base interaction plays a major role in membrane fouling.
To further determine the fouling behavior of bovine serum albumin (BSA) on different hydrophilic PVDF ultrafiltration (UF) membranes over a range of pH values, self-made atomic force microscopy (AFM) colloidal probes were used to detect the adhesion forces of membrane–BSA and BSA–BSA, respectively. Results showed that the membrane–BSA adhesion interaction was stronger than the BSA–BSA adhesion interaction, and the adhesion force between BSA–BSA-fouled PVDF/PVA membranes was similar to that between BSA–BSA-fouled PVDF/PVP membranes, which indicated that the fouling was mainly caused by the adhesion interaction between membrane and BSA. At the same pH condition, the PVDF/PVA membrane–BSA adhesion force was smaller than that of PVDF/PVP membrane–BSA, which illustrated that the more hydrophilic the membrane was, the better antifouling ability it had. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory predicts that the polar or Lewis acid–base (AB) interaction played a dominant role in the interfacial free energy of membrane–BSA and BSA–BSA that can be affected by pH. For the same membrane, the pH values of a BSA solution can have a significant impact on the process of membrane fouling by changing the AB component of free energy.
A novel photocatalytic Ag-Cu-TiO2 nanowire membrane was fabricated.
Bacteria and virus disinfection was improved by co-depositing Ag and Cu onto membrane.
Synergetic photocatalytic effects and free metal ions of Ag and Cu contribute to disinfection.
7.68 log removal of E. coli and 4.02 log removal of bacteriophage MS2 were achieved.
Titanium dioxide (TiO2) is a widely used photocatalyst that has been demonstrated for microorganism disinfection in drinking water. In this study, a new material with a novel structure, silver and copper loaded TiO2 nanowire membrane (Cu-Ag-TiO2) was prepared and evaluated for its efficiency to inactivate E. coli and bacteriophage MS2. Enhanced photo-activated bactericidal and virucidal activities were obtained by the Cu-Ag-TiO2 membrane than by the TiO2, Ag-TiO2 and Cu-TiO2 membranes under both dark and UV light illumination. The better performance was attributed to the synergies of enhanced membrane photoactivity by loading silver and copper on the membrane and the synergistic effect between the free silver and copper ions in water. At the end of a 30 min test of dead-end filtration under 254 nm UV irradiation, the Cu-Ag-TiO2 membrane was able to obtain an E. coli removal of 7.68 log and bacteriophage MS2 removal of 4.02 log, which have met the US EPA standard. The free metal ions coming off the membrane have concentrations of less than 10 ppb in the water effluent, far below the US EPA maximum contaminant level for silver and copper ions in drinking water. Therefore, the photo-activated disinfection by the Cu-Ag-TiO2 membrane is a viable technique for meeting drinking water treatment standards of microbiological water purifiers.
The Green House program reduced the amount of waste by 34%.
The Green House is now running with a monthly loss of 1982 CNY.
Involve government, expand scale, use professional technology are main suggestions.
Improved program can reduce the amount of waste by 37% (33.8 tons monthly).
Improved program can flip the loss into a profit worth 35034 CNY monthly.
Although Beijing has carried out municipal solid waste (MSW) source separation since 1996, it has largely been ineffective. In 2012, a “Green House” program was established as a new attempt for central sorting. In this study, the authors used material flow analysis (MFA) and cost benefit analysis (CBA) methods to investigate Green House’s environment and economic feasibility. Results showed that the program did have significant environmental benefits on waste reduction, which reduced the amount of waste by 34%. If the Green House program is implemented in a residential community with wet waste ratio of 66%, the proportion of waste reduction can reach 37%. However, the Green House is now running with a monthly loss of 1982 CNY. This is mainly because most of its benefits come from waste reduction (i.e., 5878 CNY per month), which does not turn a monetary benefit, but is instead distributed to the whole of society as positive environmental externalities. Lack of government involvement, small program scale, and technical/managerial deficiency are three main barriers of the Green House. We, thus, make three recommendations: involve government authority and financial support, expand the program scale to separate 91.4 tons of waste every month, and use more professional equipment/technologies. If the Green House program can successfully adopt these suggestions, 33.8 tons of waste can be reduced monthly, and it would be able to flip the loss into a profit worth 35034 CNY.
Phenol removal by n/m Fe in the presence of H2O2 was highly effective.
Increasing the amounts of n/m Fe and H2O2?increased the phenol removal rate.
Phenol removal was decreased with an increase in the concentration of phenol.
The natural pH (6.9) of the solution was highly effective for phenol removal.
The pseudo-first-order kinetics was best fitted for the degradation of phenol.
The study investigates the magnetic separation of Fe from automobile shredder residue (ASR) (<0.25 mm) and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe (n/m Fe) was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The effects of the dosages of n/mFe, pH, concentration of phenol and amount of H2O2 on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H2O2; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant (k) was increased as the amounts of n/m Fe and H2O2 increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H2O2 and n/m Fe.
Industrial waste mixed with MSW is the main source of heavy metal in bottom ash.
Chlorine content in bottom ash is controlled both by plastic and kitchen waste.
Insoluble chlorine in Chinese MSWI bottom ash exists primarily as AlOCl.
Bottom ash is an inevitable by-product from municipal solid waste (MSW) incineration plants. Recycling it as additives for cement production is a promising disposal method. However, the heavy metals and chlorine are the main limiting factors because of the potential environmental risks and corrosion of cement kilns. Therefore, investigating heavy metal and chlorine characteristics of bottom ash is the significant prerequisite of its reuse in cement industries. In this study, a correlative analysis was conducted to evaluate the effect of the MSW components and collection mode on the heavy metal and chlorine characteristics in bottom ash. The chemical speciation of insoluble chlorine was also investigated by synchrotron X-ray diffraction analysis. The results showed that industrial waste was the main source of heavy metals, especially Cr and Pb, in bottom ash. The higher contents of plastics and kitchen waste lead to the higher chlorine level (0.6 wt.%–0.7 wt.%) of the bottom ash. The insoluble chlorine in the MSW incineration bottom ash existed primarily as AlOCl, which was produced under the high temperature (1250℃) in incinerators.
Nitrogen-cycling microbial communities in municipal WWTPs were characterized.
Numbers of amoA, nirK and nirS genes were quantified by MPN-PCR.
Diversity of whole nitrogen-cycling communities was analyzed with DNA microarray.
CAS process retained diverse nitrogen cycling populations.
Specific, limited populations may be dominated in nitrogen removal processes.
To improve nitrogen removal performance of wastewater treatment plants (WWTPs), it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods:most probable number-polymerase chain reaction (MPN-PCR) and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional activated sludge processes (CAS) are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern:the nirS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectively. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes (AO), whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.
The use of PLA/starch blends for nitrogen removal was achieved.
The influence of different operating parameters on responses was verified using RSM.
The conditions for desired responses were successfully optimized simultaneously.
Blends material may have a promising application prospect in the future.
Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid (PLA)/starch blends as carbon source and carrier for functional bacteria. The exclusive and interactive influences of operating parameters (i.e., temperature, pH, stirring rate, and PLA-to-starch ratio (PLA proportion)) on nitrification (Y1), denitrification (Y2), and COD release rates (Y3) were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous nitrification and denitrification. The carbon release rate of the blends was controllable. The sensitivity of Y1, Y2, and Y3 to different operating parameters also differed. The sequence for each response was as follows: for Y1, pH>stirring rate>PLA proportion>temperature; for Y2, pH>PLA proportion>temperature>stirring rate; and for Y3, stirring rate>pH>PLA proportion>temperature. In this study, the following optimum conditions were observed: temperature, 32.0°C; pH 7.7; stirring rate, 200.0 r·min-1; and PLA proportion, 0.4. Under these conditions, Y1, Y2, and Y3 were 134.0 μg-N·g-blend-1·h-1, 160.9 μg-N·g-blend-1·h-1, and 7.6 × 103 μg-O·g-blend-1·h-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.
The bioactivity was enhanced by preozonation under low temperature conditions.
Higher level of BDOC/AOC and DO may enhance the nitrifying performance.
High level of biodiversity and bioactivity may help maintain the stability of filters.
Water quality and DO could selectively enhance different microbial communities.
The combination of preozonation and subsequent biological granular activated carbon (O3/BAC) filtration is well known as a promising method for the removal of many pollutants. Temperature and nutrients are the dominant factors in external conditions to influence the biological communities. To explore the influence of preozonation under low temperature, the factors such as dissolved oxygen (DO), dissolved organic carbon (DOC) and NH4+-N were analyzed from the sampling ports every week; triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) and the nitrifying activity were detected along the bed height of biofilter at four levels (10, 40, 70 and 110 cm) on the 90th, 110th, and 130th day; microbial community, based on 16S rRNA gene-denaturing gradient gel electrophoresis (DGGE), was monitored on the 130th day of the operation. The observed microbial property showed that preozonation had a positive influence on bioactivity, biomass and nitrifying activity. Community analysis showed no significant difference on the biodiversity of nitrifying bacteria between the parallel filters in the inlet end based on the method employed. This result showed that biofilters’ performance is not correlated well with microbial biodiversity. The elevated functionality in O3/BAC filters can be a result of increased microbial activity, which was promoted by preozonation.
Utilizing electrochemical depassivation to recovery Fe0 activity was effective, and minerals were cleaned layer by layer, with no ions secondary contamination, and no transformation from Cr(III) to Cr(VI).
Electrochemical depassivation process under various electrolysis conditions was revealed.
Electro-PRB configuration for caisson excavation construction technique was designed.
Permeable reactive barriers (PRBs) show remarkable Cr(VI) removal performance. However, the diminished removal rate because of mineral fouling over time is the bottleneck for application of PRBs. The present study demonstrated that electrochemical depassivation was effective for recovering the Fe0 reactivity, and minerals can be cleaned layer by layer with no secondary ion contamination and no transformation from Cr(III) to Cr(VI). The removal recovery rate increased with increasing electrolysis voltage before reaching the optimal electrolysis voltage, and then decreased as the electrolysis voltage further increased. The recovery effect at electrolysis voltages of 5, 10, and 15 V show the same trend as a function of electrolysis time, where recovery rate first increased and then decreased after reaching the optimal electrolysis time. The Cr(VI) removal rate significantly decreased with increasing electrolysis distance. Furthermore, Fe0 brush meshes electrode, Fe0 fillings, and polyvinyl chloride (PVC) meshes separators were combined to create an Electro-PRB configuration for the caisson excavation construction technique, which lays the foundation for establishment of promising Electro-PRB systems to treat Cr(VI)-contaminated groundwater.
Iron water treatment residues are a free by-product with high concentration of iron oxides
Iron water treatment residues has a large potential for arsenic sorption
Soils are highly contaminated by arsenic at wood preservation sites
Iron water treatment residues were added to hot spots contaminated with arsenic
The addition led to significant decrease in leaching of arsenic from the contaminated soil
Iron water treatment residues (Fe-WTR) are a free by-product of the treatment of drinking water with high concentration of iron oxides and potential for arsenic sorption. This paper aims at applying Fe-WTR to a contaminated site, measuring the reduction in contaminant leaching, and discussing the design of delivery and mixing strategy for soil stabilization at field scale and present a cost-effective method of soil mixing by common contractor machinery. Soil contaminated by As, Cr, and Cu at an abandoned wood impregnation site was amended with 0.22% (dw) Fe-WTR. To evaluate the full scale amendment a 100 m2 test site and a control site (without amendment) were monitored for 14 months. Also soil analysis of Fe to evaluate the degree of soil and Fe-WTR mixing was done. Stabilization with Fe-WTR had a significant effect on leachable contaminants, reducing pore water As by 93%, Cu by 91% and Cr by 95% in the upper samplers. Dosage and mixing of Fe-WTR in the soil proved to be difficult in the deeper part of the field, and pore water concentrations of arsenic was generally higher. Despite water logged conditions no increase in dissolved iron or arsenic was observed in the amended soil. Our field scale amendment of contaminated soil was overall successful in decreasing leaching of As, Cr and Cu. With minor improvements in the mixing and delivery strategy, this stabilization method is suggested for use in cases, where leaching of Cu, Cr and As constitutes a risk for groundwater and freshwater.
In the paper concepts for wastewater treatment of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration.
In the paper concepts for domestic wastewater treatment plants of the future are discussed by the use of a) one flow diagram based on established, compact, proven technologies (i.e. nitrification/denitrification for N-removal in the mainstream) and b) one flow diagram based on emerging, compact technologies (i.e. de-ammonification in the main stream).The latter (b) will give an energy-neutral wastewater treatment plant, while this cannot be guaranteed for the first one (a). The example flow diagrams show plant concepts that a) minimize energy consumption by using compact biological and physical/chemical processes combined in an optimal way, for instance by using moving bed biofilm reactor (MBBR) processes for biodegradation and high-rate particle separation processes, and de-ammonification processes for N-removal and b)maximize energy (biogas) production through digestion by using wastewater treatment processes that minimize biodegradation of the sludge (prior to digestion) and pretreatment of the sludge prior to digestion by thermal hydrolysis. The treatment plant of the future should produce a water quality (for instance bathing water quality) that is sufficient for reuse of some kind (toilet flushing, urban use, irrigation etc.). The paper outlines compact water reclamation processes based on ozonation in combination with coagulation as pretreatment before ceramic membrane filtration.
We modeled the impact of haze radiative effects on precipitation in North China.
Shortwave heating induced by haze radiative effects would reduce heavy rainfalls.
Convection was the key factor that whether precipitation was enhanced or suppressed.
Precipitation was often suppressed where CAPE, RH and updraft velocities were high.
The impact of haze radiative effect on summertime 24-h convective precipitation over North China was investigated using WRF model (version 3.3) through model sensitivity studies between scenarios with and without aerosol radiative effects. The haze radiative effect was represented by incorporating an idealized aerosol optical profile, with AOD values around 1, derived from the aircraft measurement into the WRF shortwave scheme. We found that the shortwave heating induced by aerosol radiative effects would significantly reduce heavy rainfalls, although its effect on the post-frontal localized thunderstorm precipitation was more diverse. To capture the key factors that determine whether precipitation is enhanced or suppressed, model grids with 24-h precipitation difference between the two scenarios exceeding certain threshold (>30 mm or<-30 mm) were separated into two sets. Analyses of key meteorological variables between the enhanced and suppressed regimes suggested that atmospheric convection was the most important factor that determined whether precipitation was enhanced or suppressed during summertime over North China. The convection was stronger over places with precipitation enhancement over 30 mm. Haze weakened the convection over places with precipitation suppression exceeding 30 mm and caused less water vapor to rise to a higher level and thus further suppressed precipitation. The suppression of precipitation was often accompanied with relatively high convective available potential energy (CAPE), relative humidity (RH) and updraft velocities.
