Water Treatment Performance Research Articles

Nanomaterials Based Drinking Water Purification: Comparative Study with a Conventional Water Purification Process

One of the ways of fully securing the presence of fresh water is water treatment process. Nanomaterials and nanotechnology offers an innovative solution for water treatment. In this study, physical, chemical and microbiological improvement rates of raw water were analyzed after filtration with graphene oxide. Graphene oxide's water treatment performance; silver nanoparticles, silver nanoparticles & graphene oxide composites that are commonly used in water treatment were compared with a traditional treatment method. When compared to the traditional method, there were improvements of 50 %, 40.7 %, 86.8 % and 45.5 % for color, TIC, TOC and hardness properties, respectively in water treatment by GO-based filtration with solid liquid ratio of 0.7 % (v/v). In water treatment with GO-Ag based filtration, 39.8 %, 69.8 %, 10.3 % and 28.6 % of improvements were obtained for TIC, TOC, hardness and LSI value compared to the conventional method. Both GO at 0.7 % (v/v) solid-liquid ratio and GO-Ag nanocomposites were successful in the number of total viable microorganisms and inhibiting microorganisms such as Escherichia coli fecal (gaita-infected), Salmonella typhi, Enterococcus faecalis, Pseudomona aeruginosa and Staphylococcus aureus. Among the studied parameters GO-Ag nanocomposites found to be the most suitable for drinking water treatment.

Optimisation and improvement of in-line filtration performance in water treatment for a typical low turbidity source water

ABSTRACTForest catchments can produce high quality source water with a low turbidity. However, the combination of low turbidity, low organic carbon, and low temperature water conditions presents operating challenges in conventional water treatment processes. In this study, in-line filtration was tested using pilot-scale filter columns, and was found to be an appropriate option to treat a typical low turbidity water originating from the Rocky Mountains near Calgary, Alberta, Canada. When alum and cationic polymer were dosed simultaneously, in-line filtration produced high quality effluent with a turbidity and a particle count value of less than 0.1 NTU and 50 counts/mL, respectively. However, the alum and polymer doses and their ratios played important roles in the filtration efficiency. In general, short filter ripening times (i.e. <15 min) required an alum dose of at least 3 mg/L and an alum to polymer dose ratio of less than 180:1. A longer filter stable period was associated with lower alum and polymer doses, as long as their doses were at least 2 and 0.024 mg/L, respectively, and their dose ratio was maintained in the range of 30:1 to 130:1. The optimal alum and polymer doses were observed to be 3 and 0.072 mg/L, respectively. Filter performance was enhanced when higher alum and polymer doses were used for ripening, and lower doses were applied during the stable filtration period. In addition, in-line filtration resulted in the reduction of microspheres by 3.6 logs under the tested water conditions. Hence, a similar removal efficiency is anticipated for Cryptosporidium.

A separation-free polyacrylamide/bentonite/graphitic carbon nitride hydrogel with excellent performance in water treatment

Abstract 3D-hydrogels have broad potential for wastewater treatment, for they are separation-free and have excellent adsorption capacity. However, the process of adsorption is only the enrichment of pollutants rather than elimination. Development of 3D-hydrogel/photocatalyst composite materials is a promising strategy for achieving the enrichment and mineralization of organic pollutants. This paper describes a facile and environmentally friendly synthesis of separation-free polyacrylamide/bentonite/graphitic carbon nitride 3D-hydrogel. When the mass of graphitic carbon nitride is 1/10 of acrylamide, the composite hydrogel displays excellent removal of tetracycline in both static and flowing state. The total removal efficiency is higher than that of adsorption or degradation. The enhanced removal of organic pollutants is attributed to the synergistic effect of adsorption and photocatalytic degradation, the enhanced light absorption and the accelerated separation of photogenerated charge carriers. More importantly, it has excellent stability and can be easily separated from water and reused. This 3D-hydrogel/photocatalyst composite materials has broad application potential to the elimination of organic pollutants in water.

Comparison of photo-Fenton, O3/H2O2/UV and photocatalytic processes for the treatment of gray water

This research was carried out to compare and optimize the gray water treatment performance by the photo-Fenton, photocatalysis and ozone/H2O2/UV processes. Experimental design and optimization were carried out using Central Composite Design of Response Surface Methodology. The results of experiments showed that the most effective and influencing factors in photo-Fenton process were H2O2/Fe2+ ratio, in ozone/H2O2/UV experiment were O3 concentration, H2O2 concentration, reaction time and pH and in photocatalytic process were TiO2 concentration, pH and reaction time. The highest COD removal in photo-Fenton, ozone/H2O2/UV and photocatalytic process were 90%, 92% and 55%, respectively. The results were analyzed by design expert software and for all three processes second-order models were proposed to simulate the COD removal efficiency. In conclusion the ozone/H2O2/UV process is recommended for the treatment of gray water, since it was able to remove both COD and turbidity by 92% and 93%, respectively.

An automated on-line turbulent flow liquid-chromatography technology coupled to a high resolution mass spectrometer LTQ-Orbitrap for suspect screening of antibiotic transformation products during microalgae wastewater treatment

The evaluation of wastewater treatment capabilities in terms of removal of water pollutants is crucial when assessing water mitigation issues. Not only the monitoring of target pollutants becomes a critical point, but also the transformation products (TPs) generated. Since these TPs are very often unknown compounds, their study in both wastewater and natural environment is currently recognized as a tedious task and challenging research field. In this study, a novel automated suspect screening methodology was developed for a comprehensive assessment of the TPs generated from nine antibiotics during microalgae water treatment. Three macrolides (azithromycin, erythromycin, clarithromycin), three fluoroquinolones (ofloxacin, ciprofloxacin, norfloxacin) and three additional antibiotics (trimethoprim, pipemidic acid, sulfapyridine) were selected as target pollutants. The analysis of samples was carried out by direct injection in an on-line turbulent flow liquid chromatography-high resolution mass spectrometry (TFC-LC-LTQ-Orbitrap-MS/MS) system, followed by automatic data processing for compound identification. The screening methodology allowed the identification of 40 tentative TPs from a list of software predicted intermediates created automatically. Once known and unknown TPs were identified, degradation pathways were suggested considering the different mechanisms involved on their formation (biotic and abiotic). Results reveal microalgae ability for macrolide biotransformation, but not for other antibiotics such as for fluoroquinolones. Finally, the intermediates detected were included into an in-house library and applied to the identification of tentative TPs in real toilet wastewater treated in a microalgae based photobioreactor (PBR). The overall approach allowed a comprehensive overview of the performance of microalgae water treatment in a fast and reliable manner: it represents a useful tool for the rapid screening of wide range of compounds, reducing time invested in data analysis and providing reliable structural identification.

Improving the biological treatment of waste water using pressurised sequencing batch reactor

Pollution is one of the major problems that mankind faces nowadays. Society’s expectations of waste water treatment have evolved over time. While protecting aquatic environment and public health continues to be a paramount concern, the desire to recover clean water, energy and useful resources from waste water is getting increasingly stronger today. The current study aims to reduce the pollution of water and air resulting from the biological treatment process by using a new technique (pressurised sequencing batch reactor (SBR) model) through improvement of waste water treatment performance and control of the surplus air resulting from the aeration process and reusing it more than once in the aeration process. The results showed that the pressurised SBR model compared with conventional SBR model enhanced the biochemical oxygen demand removal, the total suspended solids removal and total dissolved solids removal by 6, 8 and 12%, respectively, at a gauge pressure of 0·5 atm and by about 9, 15 and 19%, respectively, at a gauge pressure of 2 atm. In addition, the enhancement in the nitrogen and phosphorus removal was remarkable.

The electro-peroxone process for the abatement of emerging contaminants: Mechanisms, recent advances, and prospects

The electro-peroxone (E-peroxone) process is an emerging electrochemical advanced oxidation process (EAOP) that combines ozonation with in situ cathodic hydrogen peroxide (H2O2) production to drive the peroxone reaction for water and wastewater treatment. Over the past several years, the E-peroxone process has quickly emerged as a promising EAOP for the abatement of emerging contaminants (ECs) in water. Because of the enhanced ozone (O3) transformation to hydroxyl radicals (OH) by electro-generated H2O2, the E-peroxone process can considerably increase the efficiency and decrease the energy demand for the abatement of ozone-resistant ECs compared with conventional ozonation. Meanwhile, the E-peroxone process can substantially mitigate the formation of bromate during the treatment of bromide-containing water, which has been a major concern of conventional ozonation for water treatment. Hence, by simply installing electrodes in ozone contactors, the E-peroxone process can remarkably enhance the performance of water and wastewater treatment in various aspects. Compared with other ozone-based AOPs such as the conventional peroxone (O3/H2O2) and UV/O3 processes, the E-peroxone process also represents a more convenient, cost-effective, energy-efficient, and safer option for EC abatements. This paper reviews recent research of the E-peroxone process, with focus on the abatement of ECs in real water matrices. The fundamental reaction mechanisms that are essential to the understanding, design, and operation of the E-peroxone process are described. The abatement of various ECs in natural water and wastewater by the E-peroxone process are critically reviewed. The challenges in scaling-up the E-peroxone process and integrating it in water and wastewater treatment trains for practical applications are discussed.

Application and mechanism of polysaccharide extracted from Enteromorpha to remove nano-ZnO and humic acid in coagulation process

Enteromorpha polysaccharide (Ep) extracted from alga a novel green coagulant aid for nanoparticles (NPs) and heavy metal ions removal and the structure of EP was intensively studied in this study. The integration of Ep with polyaluminum chloride (PAC-Ep) coagulants exhibited higher coagulation performance than that of the polyaluminum chloride (PAC) because of the negatively charged NPs suspension and humic aid (HA) solution. Significant high removal efficiencies of dissolved organic matter (94.1%), turbidity (99.3%) and Zn ions (69.3%) were achieved by the PAC-Ep coagulants. The dual-coagulation properties of PAC-Ep for different pollutants was based on multiple mechanisms, including (i) Al3+ charge neutralization; (ii) hydroxy aluminum hydroxyl bridging formed polynuclearhydroxy complexes bridge and sweep colloidal particles; (iii) adsorption and bridging of Ep chain for the NPs and heavy metal ions. Results indicated that the destabilization of colloid was induced by the coexisting HA and higher removal was achieved as ions adsorption was enhance in the presence of HA complexation. On the basis of that, the extraction of polysaccharide is a promising candidate for its high coagulation performance in water treatment.

Human health impact of non-potable reuse of distributed wastewater and greywater treated by membrane bioreactors

We assessed the annual probability of infection resulting from non-potable exposures to distributed greywater and domestic wastewater treated by an aerobic membrane bioreactor (MBR) followed by chlorination. A probabilistic quantitative microbial risk assessment was conducted for both residential and office buildings and a residential district using Norovirus, Rotavirus, Campylobacter jejuni, and Cryptosporidium spp. as reference pathogens. A Monte Carlo approach captured variation in pathogen concentration in the collected water and pathogen (or microbial surrogate) treatment performance, when available, for various source water and collection scale combinations. Uncertain inputs such as dose-response relationships and the volume ingested were treated deterministically and explored through sensitivity analysis. The predicted 95th percentile annual risks for non-potable indoor reuse of distributed greywater and domestic wastewater at district and building scales were less than the selected health benchmark of 10−4 infections per person per year (ppy) for all pathogens except Cryptosporidium spp., given the selected exposure (which included occasional, accidental ingestion), dose-response, and treatment performance assumptions. For Cryptosporidium spp., the 95th percentile annual risks for reuse of domestic wastewater (for all selected collection scenarios) and district-collected greywater were greater than the selected health benchmark when using the limited, available MBR treatment performance data; this finding is counterintuitive given the large size of Cryptosporidium spp. relative to the MBR pores. Therefore, additional data on MBR removal of protozoa is required to evaluate the proposed MBR treatment process for non-potable reuse. Although the predicted Norovirus annual risks were small across scenarios (less than 10−7 infections ppy), the risks for Norovirus remain uncertain, in part because the treatment performance is difficult to interpret given that the ratio of total to infectious viruses in the raw and treated effluents remains unknown. Overall, the differences in pathogen characterization between collection type (i.e., office vs. residential) and scale (i.e., district vs. building) drove the differences in predicted risk; and, the accidental ingestion event (although modeled as rare) determined the annual probability of infection. The predicted risks resulting from treatment malfunction scenarios indicated that online, real-time monitoring of both the MBR and disinfection processes remains important for non-potable reuse at distributed scales. The resulting predicted health risks provide insight on the suitability of MBR treatment for distributed, non-potable reuse at different collection scales and the potential to reduce health risks for non-potable reuse.

Analisis Pengelolaan Air Bekas Wudhu’ Jamaah Mesjid Jamik Lambaro Kabupaten Aceh Besar

Used water has the potential to be processed and recycled based on its continuous volume and quality that allows processing in place. The need for the importance of water is not balanced with consciousness to conserve water, so that many sources of water are polluted by human actions themselves. The purpose of this study is to determine the level of waste water usage of ablution activities, to know the performance of water treatment using ablution water through a combination of slow sand filter; and analyze the content of BOD5, E.colli / total coliform, pH and ablution water temperature. This research took samples at Jamik Lambaro Mosque, Regency of Aceh Besar, then tested in Environmental Engineering Laboratory of Environment of Serambi Mekkah University. The results showed that the use of ablution water increased at the time of five daily prayers, especially on Friday reached 1,579 people with the use of water ablution reached 4747 liters. Currently, there is no water treatment for the former Mosque of Jami’ Lambaro Mosque, the waste water is dumped into the mosque’s drainage ditch. Based on ablution water treatment with sand combination has decrease efficiency of BOD5 equal to 95%. The results of laboratory tests showed that the BOD5 content of 17 mg / l, its value under the standard quality of 50 mg / l. E.colli / total coliform that is 0 from 100 ml that meets the quality standard in accordance with Kep.Men LH RI No. 5 year 2014. The result of temperature / temperature analyst is 28,9 oC and pH is 7,34

Optimisation of lightweight green wall media for greywater treatment and reuse

Green walls are increasingly being considered as a suitable greywater treatment technology. Nevertheless, until now there have been no clear recommendations for the use of effective lightweight media in greywater treating green walls. Previous studies of potentially suitable growing media have suggested that a combination of perlite and coco coir might be the most effective for these novel systems. However, there is no clear understanding of what proportion of perlite and coir should be used and how different mixes would affect greywater treatment. This work tested the hydraulic and pollutant removal performance of six different perlite and coco coir media mixes in an unvegetated column experiment. The results suggested that there is a point between 2:1 and 3:1 ratios of perlite to coir where the infiltration rate significantly increases, as the result of perlite dominance. As the infiltration rate increases, the mix gets less prone to clogging, but this negatively affects pollutant removal performance, with insufficient time for biological processes. We therefore optimised the mix for effective long-term treatment of total suspended solids, total nitrogen, chemical oxygen demand and Escherichia coli. Unfortunately, total phosphorus removal from greywater was limited for all tested mixes. This study also showed that attention should be given to greywater inflow dynamics and expected daily water treatment capacity; e.g. systems with a lower hydraulic loading were able to use greater proportion of coir in the mix achieving greater water treatment performance, while systems with higher hydraulic loadings require faster flowing mixes with lower coir proportion.

Hydrothermal fabrication of TiO2-MoO3 nanocomposites with superior performance for water treatment

TiO2-MoO3 nanocomposites have been hydrothermally fabricated at 180 °C using (NH4)6Mo7O24⋅ 4H2O and TiCl4 as the Mo and Ti source, respectively. The TiO2 and MoO3 nanocrystalline can be confirmed in the products with the X-ray diffraction (XRD). Transmission electron microscopy (TEM) clear showed that the size of MoO3becomes smaller with the increase of the Ti-doping amount. The MoO3 was embraced by anatase TiO2 nanoparticles with an average size of 10 nm. The TiO2-MoO3 nanocomposites showed good adsorption activity for Rhodamine B (RhB) is approximately 290 mg g−1, Methylene blue (MB) and the Cr(VI) of heavy metal ion are 180 mg g−1 and 59 mg g−1, respectively.

Biogas Productivity as Renewable Energy and Performance of Waste Water Treatment in Tofu Small Scale Industry using an AnSBR Reactor

A research that analyzed the relationship between biogas production as renewable energy and performance of waste water treatment in tofu small industry using AnSBR reactor has been conducted. This research used system operation method in batches in to get a description of how the biogas production system works as it was operated in the batch mode, which is applied in tofu industry. An instrument capable of operation in batch mode using AnSBR reactor was designed as it does not require sludge re-circulation. An AnSBR reactor includes five stages of; filling, reaction, settling, decanting, and stabilization (idling state). The research was run for 24 days using biogas collected in a tank. Biogas was measured for each HRT starting on the second day HRT to 24th day HRT. Biogas characteristics were monitored on day 16th for contents of CH4, CO2 and heat value. Results show that CH4 content in the biogas amounts to 78.26 %, while CO2 comprises 20.16 %. Meanwhile, the heat value, which depends on acid methane and CO2 content, is 4,246.55 kkal/kg.

The investigation of the specific behavior of a cationic block structure and its excellent flocculation performance in high-turbidity water treatment.

The fabrication of a cationic polyacrylamide (CPAM) with high efficiency and economy has been highly desired in the field of high-turbidity water treatment. This study introduced an ultrasound (US)-initiated template polymerization (UTP) method to develop a novel cationic templated polyacrylamide (TPAA) with a microblock structure. TPAA was prepared using acrylamide (AM) and sodium (3-acrylamidopropyl)trimethylammonium chloride (ATAC) as the monomers and sodium polyacrylate (NaPAA) as the template. Factors that affected polymerization such as the ultrasound power, ultrasound time, initiator concentration, pH, and mAM : mATAC and nNaPAA : nATAC values were investigated. The properties of the polymers were characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicated the successful formation of a cationic microblock structure in TPAA. In addition, TPAA displayed favorable thermal decomposition properties and a rough and coarse surface morphology, as shown by analyses using TGA and SEM, respectively. Moreover, a zip (type I) template polymerization mechanism was identified via analyses of the association constant (KM), conversion (Cv) and polymerization rate (Rp). The flocculation performance of the templated copolymer TPAA was evaluated by treating high-turbidity water. According to the results for the zeta potentials and FTIR spectra of the generated flocs, it was indicated that the cationic microblocks in the templated copolymer could greatly enhance its charge neutralization, patching and bridging ability, and therefore excellent flocculation performance (residual turbidity: 5.8 NTU, Df: 1.89, floc size d50: 608.404 μm and floc kinetic: 15.86 × 10−4 s−1) for treating high-turbidity water was achieved.

One-step fabrication of boron nitride fibers networks

The three dimensional boron nitride monolith with fibers network architecture was fabricated through directly pyrolyzing the assembly of the C3N6H6·2H3BO3 green fibers. This one-step way is superior to the typical techniques using hydrophobic and agglomerate BN micro-/nano- materials to construct architectures. The obtained BN monolith exhibited low density of 92mgcm−3 with high porosity (94.45vol%), as well as robust skeleton with high compressive strength (σf = 42.54kPa) and stiffness (E = 0.475MPa). The BN network also displayed hydrophobicity with water contact angle of 136.9° and oleophilicity with rapid oil permeation. It showed great performance in oily water treatment. Furthermore, the robust BN network would also be potential as catalyst supports, composites reinforcements and filters in many practical applications.

Preparation and Application of Carboxylated Graphene Oxide Sponge in Dye Removal.

Spongy graphene is a newly developed adsorbent of high performance for water treatment. Proper functionalization is an efficient approach to improve the adsorption capacity of graphene adsorbents. In this study, we prepared graphene oxide (GO), functionalized it with carboxyl groups to produce carboxylated GO (GO-COOH) dispersion, and lyophilized the GO-COOH dispersion to obtain the GO-COOH sponge. The adsorption isotherm, kinetics, thermodynamics, influencing factors, and regeneration of the adsorption of dye methylene blue (MB) on GO-COOH sponge were evaluated in batch experiments. The adsorption capacity of GO-COOH sponge was measured as 780 mg/g, which was nearly twice that of GO sponge (446 mg/g). The adsorption isotherm could be well described by the Freundlich model with a KF of 508 (L/mg)1/n. The adsorption kinetic was nicely fitted by pseudo-first-order model with a k1 of 0.00157·min−1. In thermodynamics analysis, the negative ΔG indicated the spontaneous nature of adsorption on GO-COOH sponge. The adsorption process was endothermic and was driven by the increase of entropy. Higher pH benefited the removal of MB by GO-COOH sponge and the ionic strength had no meaningful effect. The regeneration was poor due to the strong electrostatic interaction between MB and the GO-COOH sponge. The results collectively suggested that carboxylation increased the adsorption performance of GO sponge.

Assessing pre-adsorption time impact on ultrafiltration performance for surface water treatment

Abstract This study was to assess the effect of powdered activated carbon (PAC) pre-adsorption time on ultrafiltration performance for surface water treatment. Experimental results demonstrated that membrane fouling could be mitigated by extending the pre-adsorption time. The molecular weight (MW) distribution of water samples was determined by liquid chromatography – organic carbon detector (LC-OCD) and results showed that the mechanism of PAC controlling fouling was attributed to a decrease in the low molecular weight (LMW) fraction of raw water via extending the pre-adsorption time. Fouling indexes (FIs) were used to evaluate membrane fouling potential and the results showed that polysaccharides (PS) and proteins (PN) were greatly responsible for membrane fouling. Therefore, prolonging the PAC pre-adsorption time and decreasing the PS and PN content in raw water are the main measurement for the alleviation of membrane fouling when PAC is used as the pretreatment in waterworks.

Fabrication of nanostructured flowerlike p-BiOI/p-NiO heterostructure and its efficient photocatalytic performance in water treatment under visible-light irradiation

Bismuth-related nanomaterials have received intense attention as potential promising photocatalysts for environment remediation. BiOI is well-known due to efficient photocatalytic activity, high stability, low cost and nontoxicity. In this study, novel nanostructured high-yield visible-light-induced photocatalyst p-BiOI/p-NiO was synthesized by a facile solvothermal method. Several characterization methods, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), Fourier Transform Infrared Spectroscopy (FTIR), the Brunauer–Emmett–Teller (BET) surface area, photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS) were employed to study the phase structures, morphologies and optical properties of the samples. The photocatalytic properties of the as-prepared products were measured with the degradation of acid orange 7 (AO7) at room temperature under visible light illumination. It was found that the NiO amount in the BiOI/NiO composites played an important role in the corresponding photocatalytic properties. The best performance was achieved at 10% content. Enhanced photocatalytic activity of the composites was due to the improved photogenerated carrier separation capacity due to suitable heterojunction formation. In addition the mechanism was proposed for the coupled semiconductors. The reusability of nanophotocatalyst and effects of pH, dye concentration and photocatalyst dosage were also investigated.

Analysis of Microbial Diversity in a Fluidized-Sand Biofilter Based on High-Throughput Sequencing Technology

In order to understand the microbial community composition and mechanism of purifying aquaculture water with a biofilter that was been applied to spotted parrotfish recirculating aquaculture systems with microglass beads as the biofilter filler, the changes in the nutrients of different biological filter beds and the water treatment performance of a fluidized-sand biofilter were analyzed. By using high-throughput sequencing technology, the microbial community structure of the surface area and bottom area at different times were studied. The results show that the fluidized-sand biofilter successfully start-up after one month under marine culture. Nitrification of the biofilter occurred mainly in the lower bed layer; the surface area played a small role in eliminating the NH4+-N. The average removal rates of NH4+-N, TN, BOD5, and SS were 68.3%±2.24%, 49.54%±3.56%, 60.35%±4.98%, and 45.21%±2.11%, respectively. The average NH4+-N removal load reached (343.28±75.5) g·(m3·d)-1, which showed a better performance of wastewater treatment. In this experiment, 31 phyla and 490 genera were identified, thus the biological diversity was significantly higher than that of the other conventional microbial biofilter. Start-stop cycling of the self-cleaning device in the biofilter had no effect on the microbial diversity of different regional, but had some effect on the dominant bacterial community of the microglass beads surface. Under opening self-cleaning device regularly condition, the microbial species of the surface and bottom areas became significantly similar. With time, the microbial species of the superficial area and bottom area had no significant change, and the microbial population structure was relatively stable. In the biofilm training period, the diversity of microbial communities was significantly lower than it was after biofilm maturation. At the time of biofilter stable operation, the dominant bacteria of the superficial zone essentially remained unchanged and mainly included Anaerolineaceae_uncultured (8.4%-28%), Flavobacteriaceae_unclassified (1.1%-32%), Rhodobacteraceae_uncultured (2.3%-17%), Nitrospira(1%-7%), and Caldilineaceae_uncultured (1%-6%). The dominant bacteria of the bottom zone changed over time and mainly include Nitrospira (12.45%-17.06%), Candidatus_Microthrix (2.6%-8.8%), Muricauda (4.8%-6.3%), Defluviimonas (6%-7%), and Rhodobacteraceae_uncultured (2%-6.2%). Among them, the abundance of Nitrospira was significantly higher than that in the other biofilter.

Effect of feed water characteristics on nanofiltration separating performance for brackish water treatment in the Huanghuai region of China

In this paper, one brackish groundwater quality, which represented typically the water quality in the Huanghuai region of China, was simulated and used to run a bench-scale ultrafiltration (UF)–nanofiltration (NF) system. The influences of feed pH (3.0–10.0), feed total dissolved solids (TDS) (1182–5319mgL−1) and feed dissolved organic carbon (DOC) (0.54–2.43mgL−1) on the separating efficiencies of two different NF membranes (Thin-Film Composite (DL) and Polyamide (DK)) were investigated. In addition, long-term operation for 580h was also conducted by the superior NF membrane to evaluate the performance stability and fouling potential after a number of subsequent cleaning cycles. Within the scope of the test, NF separating performance in terms of salt rejection showed different changing tendencies: V-shaped curve for pH, inverted V-shaped curve for TDS and linear curve for DOC. While in general, specific permeate flux was reduced in different degrees except for DK membrane with feed pH variation. The observed separating performance decline with operating time was mainly due to the scale formation on the NF membrane surface, which was rinsed effectively (FR1=97.80% and RR1=61.63%; FR2=95.40% and RR2=49.35%) by chemical cleaning, as certified by FESEM−EDX and AFM images.