Application of MFI-UF fouling index with NOM fouling under various operating conditions

Fouling research with polymeric membranes has demonstrated that various natural organic matter (NOM) fractions contribute differentially to membrane fouling behavior. However, limited studies exist analyzing the sensitivity of the MFI-UF to be used as a tool to differentiate NOM fouling components. The results here indicate that MFI-UF is a suitable tool for assessing NOM fouling. Specifically, NOM fouling potential was in the order of organic proteins (as BSA), polymers (alginate), and humic acid, respectively. Further, a mixed solution containing BSA, alginate and humic acid fouled similarly to the BSA solution indicating the high fouling potential of organic proteins in membrane systems. The MFI-UF value was found to increase by > 30% with increasing pressure (1–3 bar) and decreasing temperature (35°C–5°C). The filtered water volume was found to correlate with the MFI-UF values indicating the dependency of the method on testing conditions. Incorporating water viscosity and pressure values against normalized conditions (20°C and 2 bar) with the standard MFI-UF equation was found to be useful to estimate MFI-UF values at variable operating conditions, thus, enhances the potential application range of MFI-UF as a fouling index for NOM

Comparative analysis of physical cleaning operations for fouling control of hollow fiber membranes in drinking water treatment

The combined effect of air scouring, backwashing and relaxation on the fouling reduction of a hollow fiber PVDF ultrafiltration membrane was investigated using factorial designs of experiments. The investigation was carried out to test and compare the efficiency of three physical cleaning operational regimes, specially: air scour, backwashing, and relaxation. Beneficial dependencies between the operations for fouling reduction were identified and examined in this study. The use of a three operation regime under continuous flow conditions was found to be more effective for fouling reduction compared air assisted backwashing and air assisted relaxation with fouling reductions 2.5 and 3 times lower, respectively. While the use of a short backwash duration showed negligible impact on fouling reduction, a longer backwash duration was found to work in synergy with a high air flow rate and a short relaxation duration for the reduction of fouling. The use of a regime involving long backwash duration (20. s), short relaxation duration (5. min.) and high air flow rate (15. LPM) was identified as the optimal regime for fouling reduction while minimizing permeate production losses due to backwash and relaxation operations in this study

Effects of feed water temperature on irreversible fouling of ceramic ultrafiltration membranes

Temperature is known to influence the filtration performance of membrane systems through its direct impact on water viscosity. This research demonstrates that the changes in natural organic matter (NOM) fouling behavior with temperature are over and beyond simple viscosity changes in water. Constant flux experiments were performed in a tubular ceramic ultrafiltration (UF) system at 5, 20, and 35 °C. The unified membrane fouling index (UMFI) was used to identify NOM reversible and irreversible fouling mechanisms; while the modified UF fouling index (MFI-UF) was used to predict the fouling potential of NOM. The results showed that after correcting for viscosity to standard 20 °C compared to 5 °C, UMFI values were higher than expected and reflected the higher fouling irreversibility observed at the lower temperature. The lower water temperature resulted in an increase in NOM retention along with decrease in backwash and chemical cleaning effectiveness as determined by the UMFI and FEEM analyses. However, increased water temperature did not adversely impact existing backwash or chemical cleaning protocols. In addition, The MFI-UF exhibited the same trend as UMFI for establishing NOM fouling and retention, and therefore, the MFI-UF method is suitable for use as fouling predictor with ceramic membrane systems

Mechanisms and efficacy of disinfection in ceramic water filters: A critical review

Diarrheal illnesses claim the lives of hundreds of thousands of children each year, most of whom liv

Investigation into alternative raw material for cement production

This paper presents an investigation into the use of water works and wastewater (W & WW) sludge as an alternative raw material for cement production. The goal of this research was to provide a preliminary evaluation of the cementitious properties of W & WW sludge when used in the production of concrete after being sintered at different temperatures (800°C and 1100°C). Heat-treated sludge was incorporated into the manufacturing stage of concrete mortar as a replacement for a percentage of Portland cement. A series of 50 mm cube concrete prisms were cast containing different concentrations of W & WW sludge, ranging from 0 to 10%. The prisms were tested for compressive strength after curing periods of 7, 28 and 56-days. The highest heat treatment level of 1100°C showed some improvement in compressive strength up to 7.5%, however the trends were not consistent since results fluctuated between the 2.5% and 10% replacement levels. Results of wastewater sludge treated at 800°C also fluctuated between those levels. Water works sludge treated at 800°C proved to have the most beneficial effect, with compressive strengths for all replacement levels higher than the control specimens. Additional prisms were then cast using 800°C waterworks sludge and the tensile strength of the concrete was determined after seven days by means of a double-punching test. This study contributes to the increasing body of research regarding the use of W &WW in building materials, and suggests the potential benefits of its use in concrete for the purpose of sustainable infrastructure renewal

Influence of nutrient supplementation on DOC removal in drinking water biofilters

Analysis of the impacts of nitrogen, phosphorus and potassium supplementation on biofilter performance for organic carbon removal was studied on laboratory-scale biofilter columns. Three dual media biofilter columns were fed with synthetic raw water C:N:P ratios of 546:24:1, 100:10:1, and 25:5:1 (w/w) to simulate nutrient limited and two nutrient supplemented conditions, respectively. Research found that air-scour versus water only backwash improved the nutrient limited dissolved organic carbon (DOC) removal by 8%. In addition, nutrient supplementation and backwash alteration improved DOC removals by 19% for the 25:5:1 column and 14% for the 100:10:1 column. Potassium supplementation with the 25:5:1 C:N:P ratio column had no discernible effect on DOC removal. No correlation with phospholipid (7-474 nmol P/g media) and adenosine triphosphate (ATP) (0.6×105-32.74×105 pg ATP/g media) values with DOC removal were found. Nutrient availability was found to influence DOC removal, demonstrating its importance when utilizing biofiltration for treatment of source waters

Comparisons of NOM fouling and cleaning of ceramic and polymeric membranes during water treatment

This research examines the effect of various NOM fractions on ceramic and polymeric UF membranes performance in terms of fouling and cleaning. Fouling experiments were performed using five model solutions, humic acid, protein as bovine serum albumin (BSA), alginate with and without calcium, and a combined NOM mixture. Two chemical agents were selected: an oxidant (NaOCl) and caustic (NaOH). Fouling and cleaning behavior were assessed using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and fluorescence excitation and emission matrix (FEEM) analysis. The results demonstrated that NOM fouling order of the ceramic UF was similar to polymeric UF with the following trend: NOM mixture ≈BSA > alginate ±Ca+2 > humic acid. However, the backwash efficiency was 1.5×–2× higher for the ceramic UF in comparison to the polymeric UF, indicating a much higher hydraulic reversibility for the ceramic UF. A carbon mass balance in compliment with FEEM plots determined that NOM removal by the ceramic UF was ≈ 10% higher than the polymeric UF. Chemical cleaning was found to be effective for both membrane types. Thus, it was not possible to conclude, that the ceramic membrane demonstrated an advantage for chemical cleaning under the conditions studied