Micro-polluted Surface Water Research Articles

Nitrogen removal in micro-polluted surface water by the combined process of bio-filter and ecological gravel bed

Nitrogen removal in micro-polluted surface water by the combined process of a bio-filter and an ecological gravel bed was studied. Sodium acetate was added into micro-polluted surface water as carbon source and the nitrogen removal under different C/N ratio, hydraulic load and temperature were investigated. The results showed that the variations in C/N ratio, hydraulic load and temperature have significant influence on nitrogen removal in bio-filter. It was found that the denitrification rate was above 90% when C/N ratio reached 10; also, the denitrification was inhibited at low water temperature (2-10 °C); at the condition of water temperature above 20 °C, C/N ratio 10, hydraulic load 8 m(3)/(m(2) h), the combined process obtained the nitrogen removal of more than 90%, and the residual organics could be removed in ecological gravel bed.

Organic pollutants variation and antifouling enhancement with attapulgite clay addition in MBR treating micro-polluted surface water

Membrane bioreactor (MBR) is widely used in water treatment, while attapulgite clay is a kind of hydrated magnesium aluminum silicate mineral, which has a perfect sorptive quality. In order to study the effect of attapulgite clay dosed to a MBR-attapulgite clay system, compared experiments between the conventional MBR and MBR-attapulgite clay system were carried out, and the basic performance of those two MBRs was investigated. The results demonstrated that both of MBRs could remove CODMn, ammonia, UV254, TOC, and turbidity successfully. The membrane fouling in MBR-attapulgite clay system was much slight than that in MBR system, which has a longer operation time (more than 35days) before backwashing with chemical solution. While particle size distribution (PSD) showed that fine particles in mixed liquor had a strong deposit tendency on the membrane surface and membrane foulants in MBR-attapulgite clay system had much smaller size than that in the MBR. Moreover, the Zeta potential of sludge mixture in MBR-attapulgite clay system was about 11–34% lower than that in MBR. FT-IR indicates that the structure and composition of the organic matter in the mixture liquor were changed with the dosing of attapulgite. Moreover, the types and content of organic matter were also reduced, which resulted in the slow membrane fouling rate. Excitation–emission matrix (EEM) analysis proved that membrane foulants, such as aromatic amino acids, protein, and natural dissolved organic matter are decomposed more effectively by biomass in MBR-attapulgite system for a more suitable conditions supplied by attapulgite clay. SEM and component analysis demonstrated that membrane surface was covered with compact gel layer formed by organic substances and inorganic elements, such as Ca, Fe, Mg, Mn, and Si. The organic foulants coupled the inorganic precipitation enhanced the formation of gel layer and thus caused membrane fouling in the MBR.

Effect of different temperatures on performance and membrane fouling in high concentration PAC–MBR system treating micro-polluted surface water

A bench-scale immersed microfiltration coupled with 50 g/L PAC was developed to treat micro-polluted surface water (MPSW) under 10 and 20 °C and the effects of temperatures on the performance and the membrane fouling were also investigated. The low temperature (10 °C) delayed the time for the start-up by 9 days and the complete nitrification by 10 days. In the stable operation, two systems both had high NH₃-N removal efficiency (above 90%) and better removal of organic matters (10% DOC, 5% UV₂₅₄ and 4% SUVA) at 10 °C. Polysaccharides (SMP) were the main membrane fouling matters at low temperature (10 °C) and low temperature (10 °C) didn't cause serious chemical irreversible membrane fouling.

Pollutant removal mechanisms in a bio-diatomite dynamic membrane reactor for micro-polluted surface water purification

The bio-diatomite dynamic membrane (BDDM) reactor is an emerging micro-polluted surface water treatment technology that combines diatomite (the microorganism carrier) and a stainless steel mesh (the dynamic membrane support module). A constant water head of 20cm was designed to drive the BDDM filtration. The BDDM with sintered diatomite had good water penetration capacity, a filtration flux as high as 92L/m2h after a filtration time of 15,780min, and an effluent turbidity in the range of 0.15 NTU–0.20 NTU. The BDDM reactor effectively removed organic matter and ammonium nitrogen. The diatomite adsorption and the BDDM interception did not have high pollutant removal efficiencies. The dehydrogenase activity (DHA) of the bio-diatomite was in the range of 2.27–3.20(mg TF)/(gVSS)h, indicating good microorganism activity for organic matter removal. The PCR-DGGE analysis showed that the microbial community was very abundant. Bacteroidetes, Firmicutes, Proteobacteria (e.g. α-, β-, γ-proteobacteria), Verrucomicrobia, and Nitrospirae were dominant in the bio-diatomite mixed liquor and removed organic matter and ammonium nitrogen. The microbial degradation of pollutants by the bio-diatomite mixed liquor was primarily responsible for the pollutant removal in the BDDM reactor.

Pilot-Scale Test on Ozone Pre-Oxidation for Enhanced Coagulation Treatment of the Micro-Polluted Reservoir Water

Pilot scale tests are conducted to study the pre-ozonation effect of the micro-polluted surface water and its influence on the operation and treatment effects of the follow-up filtration units. The results showed that significant improvement of sand filtration performance was achieved through the use of ozone pretreatment, and the filtration cycle was nearly doubled. The THMFP removal rates of the pre-ozonation technology and the conventional technology are respectively 32% and 18%, and the former one has reduced obviously the particle number of sand filtration effluents which implied the reduced probability of detection rates of effluent microorganisms and pathogens. Long-term run effect showed that the pre-ozonation process was superior to conventional processes in CODMn and turbidity removal.

Pretreatment of micro-polluted surface water with a biologically enhanced PAC–diatomite dynamic membrane reactor to produce drinking water

Abstract This study developed a biologically enhanced powder activated carbon (PAC) diatomite dynamic membrane reactor (BPDDMR) to pretreat micro-polluted surface water for drinking water production at lab-scale in continuous mode. In the start-up operation period, the BPDDMR required approximately 26 and 31 d to achieve stable removal efficiency of CODMn and NH3–N, respectively. Turbidity was always below 0.5 NTU throughout the operation experiment in the permeate flux range of 21−54lm−2 h−1. The BPDDMR could effectively remove the hydrophilic portion of dissolved organic materials (DOM) present in the raw water. The temperature affected pollutant removal (especially CODMn), which was mainly ascribed to microbial degradation and was also enhanced by PAC and diatomite adsorption. During the precoating period, the stainless steel support mesh (aperture 74 μm) first intercepted the large PAC (50−100 μm), and then diatomite particles (5−20 μm) were intercepted to form a two-layer structure of the biologicall...

Pretreatment of micro-polluted surface water with a biologically enhanced PAC–diatomite dynamic membrane reactor to produce drinking water

Pretreatment of micro-polluted surface water with a biologically enhanced PAC–diatomite dynamic membrane reactor to produce drinking water

Removal of Cr(VI) from low-temperature micro-polluted surface water by tannic acid immobilized powdered activated carbon

In this study, food-grade tannic acid-immobilized powdered activated carbon (TA-PAC) was prepared, and adsorption of Cr(VI) (0.500mg/L) onto TA-PAC as a function of pH, contact time, adsorption capacities and adsorption isotherms at 280K was investigated. The results indicated that the immobilization process introduced abundant acid functional groups. The adsorption capacity of TA-PAC was found to be pH-dependent, and the optimal pH value was found to be 4.0. The equilibrium time was 240min for TA-PAC. Adsorption data for total chromium were modeled using both two-parameter and three-parameter isotherm models. Freundlich and linear forms of three-parameter models yielded the best results for all of the data. Desorption studies of immobilized material suggested that the immobilization of food-grade tannic acid is steady. The adsorption mechanism of Cr(VI) on TA-PAC was assumed to be a comprehensive process consisting of surface reduction of Cr(VI), esterification between catechol and chromate, and ion exchange.

Treatment of Micro-Polluted Surface Water by the Nanomaterials Modified PVDF Ultrafiltration Membrane

The PVDF ultrafiltration membrane was modified by step in situ polymerization coupled with TiO2-PANI membrane surface modifying. It has been prepared by different oxidants, such as ammonium persulfate (APS) and ferric chloride (FeCl3). Meanwhile, application of the modified PVDF ultrafiltration membrane on treating micro-polluted surface water was studied. Turbidity removal efficiency, organic compounds and ammonia nitrogen (NH3-N) were mainly concerned. The results show that the modified PVDF UF membranes can remove 95% turbidity, UV254higher than 50% which was increased greater than the original film. When FeCl3was taken as oxidant with 0.03mol/L, less by-product, NH4+, was generated than APS. Thus, the ammonia nitrogen removal rate is as high as 85.2% and is 20% more than the original film.

Bio-diatomite dynamic membrane reactor for micro-polluted surface water treatment

This work investigated the feasibility of treating micro-polluted surface water for drinking water production with a bio-diatomite dynamic membrane reactor (BDDMR) at lab-scale in continuous-flow mode. Results indicate that the BDDMR was effective in removing COD Mn, DOC, UV 254, NH 3-N and trihalomethanes' formation potential (THMFP) at a hydraulic retention time (HRT) of 3.5 h due to its high concentrations of mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS). The removal of pollutants was mainly ascribed to microbial degradation in BDDMR because the dynamic membrane alone was much less effective in pollutant removal. Though the diatomite particles (5–20 μm) were much smaller in size than the aperture of the stainless steel support mesh (74 μm), microorganisms and their extracellular polymer substances could bind these particles tightly to form bio-diatomite particles which were completely retained by the support mesh. The analysis of molecular weight (MW) distribution by gel permeation chromatography (GPC) shows that the BDDMR could effectively remove the hydrophilic fraction of dissolved organic materials present in the raw water.

Fabrication of Mesoporous N-TiO<sub>2</sub> Membrane and its Spectral Characteristics

Ceramic ultrafiltration membrane, pore size from 2 to 50nm, is of growing interest in separation and purification processes because of their higher chemical, thermal and mechanical stability compared to organic membranes. TiO2 mesoporous membranes have gained tremendous popularity due to their photocatalytic activity and because they possess high water flux and chemical resistance. In recent years, visible-light-induced nitrogen-doped titanium dioxide (N-TiO2) materials have been attracted extensive attention. We synthesized asymmetric N-TiO2 membrane based on this material via sol-gel method, in which titanium tetrabutoxide was used as Ti-precursor and formamide as nitrogen resource. A -alumina support with macropores was used and its diameter, thickness and pore size were 28.5 mm, 2.2 mm and 0.10μm, respectively. The alumina supports were pretreated using PVA to prevent permeation of sol into the supports. Sol was coated on this treated supports, and then formed gel under 60°C. The resulting membrane posseses a pore size of 4nm and its pure water permeability is 3.3L/(m2•h•bar). The influences of formamide on the microstructrue and the spectral characteristics were also analyzed by means of BET, UV-vis. As indicated by results, when the molar ratios of formamide and titanium terabutoxide were near 4, the materials had excellent visible light absorption, the absorption band was shifted to about 545nm and the band gap was reduced to 2.65eV. The band gap was 0.55eV less than that of pure TiO2. The membrane has potential application in purifing of micro-polluted surface water under visible-light environment.