Sustainable wastewater treatment and reuse in space

Exploring the vast extraterrestrial space is an inevitable trend with continuous human development.Water treatment and reuse are crucial in the limited and closed space that is available in spaceships or long-term use space bases that will be established in the foreseeable future.Dedicated water treatment technologies have experienced iterative development for more than 60 years since the first manned spaceflight was successfully launched.Herein,we briefly review the related wastewater characteristics and the history of water treatment in space stations,and we focus on future challenges and perspectives,aiming at providing insights for optimizing wastewater treatment technologies and closing the water cycle in future.

Changes of composition and antibiotic resistance of fecal coliform bacteria in municipal wastewater treatment plant

The dynamics of the composition and antibiotic resistance of the fecal coliform bacteria(FCB)in a typical wastewater treatment plant(WWTP)were investigated concerning the seasonal changes.Results showed that WWTP could remove the FCB concentration by 3∼5 logs within the effluent of 10^(4)∼10^(5)CFU/L,but the antibiotic resistant rate of FCB species increased significantly after WWTP.The dominant FCB changed from Escherichia coli in the influent(∼73.0%)to Klebsiella pneumoniae in the effluent(∼53.3%)after WWTP,where the Escherichia coli was removed the most,while Klebsiella pneumoniae was the most persistent.The secondary tank removed the most of FCB(by 3∼4 logs)compared to other processes,but increased all the concerned antibiotic resistant rate.The potential super bugs of FCB community showing resistance to all the target antibiotics were selected in the biological treatment unit of WWTP.The FCB showed the highest multiple antibiotic resistance(92.9%)in total which even increased to 100%in the effluent.Klebsiella has the highest antibiotic resistant rate in FCB,with a multiple antibiotic resistance rate of 98.4%.These indicated that the Klebsiella pneumoniae not just Escherichia coli should be specially emphasized after WWTP concerning the health risk associated with FCB community.

Chemical characteristics and water stability evaluation of groundwater in the CKDu Zone of Sri Lanka

Groundwater is the main source of drinking water for the rural population in the chronic kidney disease of unknown etiology(CKDu)zone of the North Central Province(NCP)in Sri Lanka.In this study,a total of 334 groundwater samples(311 dug wells,21 tube wells and 2 springs)during the wet season from two aquifers in the NCP were collected,and inves-tigated their chemical characteristics and evaluate their water quality,including ground-water chemistry,main ion sources,the corrosion and scaling potential of groundwater.The results showed that the two hydrochemical types of groundwater in the NCP were mainly of the Ca-HCO_(3),Na·Ca-HCO_(3)types,with the main HCO_(3)−,Na^(+)and Ca^(2+)ions in both types of groundwater originating from silicate and evaporite salt dissolution and influenced by alternating cation adsorption,while the presence of NO_(3)−was mainly anthropogenic.Eval-uation ofwater stability using namely Langelier saturation index(LSI),Ryznar stability index(RSI),Puckorius scaling index(PSI)and Larson-Skold index(LS),indicated that most ground-water presents corrosion potential and has corrosion behavior tendency of metals to some degrees.The water quality of Polonnaruwa was better than that of Anuradhapura in the NCP,and when the groundwater was worse than the“good”grade,which must be properly treated before it is used as drinking water.

Optimization of H_2O_2 dosage in microwave-H_2O_2 process for sludge pretreatment with uniform design method

A microwave-H202 process for sludge pretreatment exhibited high efticiencies of releasing organics, nitrogen, and phosphorus, but large quantifies of H202 residues were detected. A uniform design method was thus employed in this study to further optimize H202 dosage by investigating effects of pH and H202 dosage on the amount of 1-I202 residue and releases of organics, nitrogen, and phosphorus. A regression model was established with pH and H202 dosage as the independent variables, and H202 residue and releases of organics, nitrogen, and phosphorus as the dependent variables. In the optimized microwave-H202 process, the pH value of the sludge was firstly adjusted to 11.0, then the sludge was heated to 80~C and H202 was dosed at a H202 ：mixed liquor suspended solids （MLSS） ratio of 0.2, and the sludge was finally heated to 100~C by microwave irradiation. Compared to the microwave-H202 process without optimization, the H202 dosage and the utilization rate of H202 in the optimized microwave-H202 process were reduced by 80% and greatly improved by 3.87 times, respectively, when the H202：MLSS dosage ratio was decreased from 1.0 to 0.2, resulting in nearly the same release rate of soluble chemical oxygen demand in the microwave-H202 process without optimization at H202：MLSS ratio of 0.5.

Optimized pre-treatment of high strength food waste digestate by high content aluminum-nanocluster based magnetic coagulation

Coagulation-based pre-treatment efficiency of high strength digestate of food waste(HSDFW) anaerobic digestion is negated by organic ligand-catalyzed decomposition of coagulants. In this study, an efficient HSDFW pre-treatment method, magnetic seeds(MS) coagulation, was employed by using highly stable Keggin Al_(30) nanocluster(PAC_(30)), MS and polyacrylamide(PAM), and its operation was optimized by evaluating the performance of removing turbidity, total suspended solids(TSS), chemical oxygen demand(COD), and total phosphorous(TP) phosphate. Results showed that at the optimum dosage of 4.82 g/L, PAC_(30) demonstrated excellent removals as high as 98.93% ± 0.1% of turbidity, 98.04% ± 0.1% of TSS, 58.28% ± 0.3% of total COD, 99.98% ± 0.01% of TP and 99.50% ± 0.01% of dissolved phosphate, respectively. Apparent molecular weight(AMW) and three-dimensional excitation-emission matrix(3 D-EEM) fluorescence spectroscopy analyses demonstrated more efficient removal of dissolved organic matter(DOM), particularly non-biodegradable and hydrophobic components by PAC_(30) than commercial coagulant. The sedimentation was much improved from 40 min by coagulation/flocculation to about 5 min settling by MS coagulation. The PAC_(30) based magnetic coagulation(MC) presents theoretical guidance on a cost-effective and much less footprint pre-treatment alternative for high strength wastewater.

Effects of chlortetracycline,Cu and their combination on the performance and microbial community dynamics in swine manure anaerobic digestion

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline（CTC）, Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2 L anaerobic digestion reactors were established including reactor A（control）, B（CTC spiked by 0.5 g/kg dry weight, dw）, C（Cu spiked by 5 g/kg dw） and D（combination of CTC, 0.5 g/kg dw, and Cu, 5 g/kg dw）, and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion（by 30.3%）. Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C.

Advanced treatment of municipal wastewater by nanofiltration： Operational optimization and membrane fouling analysis

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration（NF） in this study. The NF performance was optimized, and its fouling characteristics after different operational durations（i.e., 48 and 169 hr） were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, p H = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight（MW） protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost.Different hydraulic retention times(72-24 h)were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater.Field experimental data from the membrane bioreactor,both full-scale(500 m/d)and pilot(1.0 m3/d),were used to calculate the net present value(NPV),incorporating both capital expenditure(CAPEX)and operating expenditure.The results showed that the tank cost was estimated above membrane cost in the 38.2%,where capital expenditure contributed 24.2%more than operational expenditure.Tank construction cost was decisive in determining the net present value contributed 62.1%to the capital expenditure.The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane,while flux decline was tolerable.The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent.The upgrade to the membrane bioreactor also benefited further treatments by 10.1%-44.7%lower direct investment.

Influence of carbon sources on nutrient removal in A2/O-MBRs： Availability assessment of internal carbon source

Both intemal carbon source and some external carbon sources were used to improve the nutrient removal in Anaerobic-Anoxic-Oxic-Membrane Bioreactor （A2/O-MBRs）, and their technical and cost analysis was investigated. The experimental results showed that the nutrient removals were improved by all the carbon source additions. The total nitrogen and phosphorus removal efficiency were higher in the experiments with external carbon source additions than that with internal carbon source addition. It was found that pathways of nitrogen and phosphorus transform were different dependent on different carbon source additions by the mass balance analysis. With extemal carbon source addition, the simultaneous nitrification and denitrification occurred in aerobic zone, and the P-uptake in aerobic phase was evident. Therefore, with addition of C-MHP （internal carbon source produced from sludge pretreatment by microwave-H2O2 process）, the denitrification and phosphorus-uptake in anoxic zone was notable. Cost analysis showed that the unit nitrogen removal costs were 57.13 CNY/kg N of C-acetate addition and 54.48 CNY/kgN of C-MHP addition, respectively. The results indicated that the C-MHP has a good technical and economic feasibility to substitute extemal carbon sources partially for nutrient removal.

Ca^2+ and SO4^2- interactions with dissolved organic matter: Implications of groundwater quality for CKDu incidence in Sri Lanka

It has recently been proposed that recalcitrant dissolved organic carbon(DOC) in groundwater plays a potent etiological role in the peculiar distribution of chronic kidney disease of unknown etiology(CKDu).This study aims to elucidate the interactions of Ca^2+and SO4^2-with a model organic fraction of humic acid(SHA) to determine the possible relationship of CKDu incidence with the DOC in drinking water.XPS and FT-IR methods respectively determined the surface functional groups and chemical composition of protonated dissolved organic carbon(HDOC) in a CKDu high-risk zone(HR) of Sri Lanka and in SHA.Higher surface C composition(87.9%) and lower O(11.4%) were observed for HDOC from the HR region than for SHA(C: 73.8%, O: 24.7%).Aromatic C with less Ocontaining functional groups was observed in HDOC.The IR band at 1170 cm^-1 confirms the formation of organic sulfonate(C–SO3^-) on SHA.A band at 1213 cm^-1 due to organic sulfonate in HDOC from the CKDu HR region was also identified.The IR band at 866 cm^-1 evidenced the formation of CaCO3 on SHA above pH 7.4.XPS data confirmed the presence of sulfur oxidation states corresponding to SO3^2-and SO4^2-at 168.9 eV and 170.1 eV binding energies,respectively.The binding energies at 347 eV and 351 eV for Ca 2p3/2 and Ca 2p1/2 eV,respectively, confirmed the bidentate complexation of Ca^2+with COO-and sulfonate groups on SHA.The organic sulfonate formed is postulated as a uremic toxicant.

Effect of non-solvent additives on the morphology,pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes

Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H2 O were used to prepare poly（vinylidene fluoride-co-chlorotrifluoroethylene）（PVDF-CTFE） hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation（DCMD） of 3.5 g/L Na Cl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol（PEG）,organic acids, Li Cl, Mg Cl2, and Li Cl/H2 O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate（DBP） showed a nonporous surface and symmetrical cross-section. When H2 O and Li Cl/H2 O mixtures were also used as additives, they were beneficial for solid–liquid demixing, especially when Li Cl/H2 O mixed additives were used. The membrane prepared with 5% Li Cl ＋ 2% H2 O achieved a flux of24.53 kg/（m2·hr） with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes.

Water environment protection and sustainable development in townlet of China: A case study in Taicang

The Environmental Kuznets Curve(EKC) model was applied to investigate the relationship between economic growth and water environment quality based on panel data of Taicang during 2010–2017. The typical inversed-U shaped relationship has been obtained between GDP(gross domestic product) and indicators of ammonia, total nitrogen(TN) and total phosphorus(TP), respectively. The EKC turning point appeared when the GDP per capita was around US$2270, which was much lower than those in some developed countries(US$11,200). However, the decoupling between chemical oxygen demand(COD) and GDP per capita occurred even before this period, which should be attributed to the strict COD emission regulation being implemented since 2010. Further, analysis based on the Tapio decoupling coefficient elasticity model analyzed the ammonia nitrogen and economic development of each industry. We found that the agriculture no-point was strong decoupling in 2011–2014, then came to Recessive decoupling. The domestic wastewater had been in a strong decoupling state;Both urban non-point and industry experienced expansive negative decoupling, due to strict policy that prioritizes the environment over development and the investment in improvement of environment and techniques, both of them gradually came to strong decoupling. The result demonstrated that the EKC turning point could be appear in earlier economic stage and the decoupling coefficient elasticity could be improved through taking strong regulation measures.

Effect of organic matter on phosphorus recovery from sewage sludge subjected to microwave hybrid pretreatment

Microwave（MW） hybrid processes are able to disrupt the flocculent structure of complex waste activated sludge,and help promote the recovery of phosphorus as struvite.In this study,to optimize struvite yield,（1） the characteristics of matter released in MW-hybrid treatments were compared,including MW,MW-acid,MW-alkali,MW-H2O2,and MW-H2O2- alkali.The results showed that selective release of carbon,nitrogen,phosphorus,Ca^2＋,and Mg^2＋ achieved by sludge pretreatment using MW-hybrid processes.MW-H2O2 is the recommended sludge pretreatment process for phosphorus recovery in the form of struvite.The ratio of Mg^2＋：NH4^＋-N：PO4^3--P was 1.2：2.9：1 in the supernatant.（2） To clarify the effects of organic matter on struvite recovery,the composition and molecular weight distribution of organic matters were analyzed.Low molecular weight COD was found to facilitate the removal rate of NH4^＋-N and PO4^3-P via crystallization,and the amorphous struvite crystals（〈1 kDa） from the filtered solutions had high purity.Therefore,the present study reveals the necessity of taking into consideration the interference effect of high molecular weight organic matters during struvite crystallization from sewage sludge.

New concept of contaminant removal from swine wastewater by a biological treatment process

Pollution from concentrated animal feeding operations(CAFOs)are the most serious pollution source in China now,and swine wastewater contains high concentrations of nutrients such as chemical oxygen demand(COD),biochemical oxygen demand 5(BOD 5),ammonium,and emergent contaminants related to public health.Biological processes are the most popular treatment methods for COD and ammonium removal.Considering the low operation cost,easy maintenance and high removal rate of contaminants in recent years,nitrogen removal via nitrite and real-time control processes using oxidation-reduction potential(ORP)and/or pH as parameters to control the aerobic and anaerobic cycles of a system has received much attention for animal wastewater treatment.During the biological treatment process,the emergent contaminants such as estrogen,antibiotics,and disinfec-tion reagents have been the focus of research recently,and degradation bacteria and resistance bacteria have also been extracted from activated sludge.The microbial analysis technique is also advancement in the field of biodegrada-tion bacteria and resistance bacteria.All of these advance-ments in research serve to improve wastewater treatment and decrease environmental hazards,especially for using manure as a fertilizer source for crop production.