Search

Iron (Fe) amended ceramic filters (CFs) have been proven to be the sustainable, low-cost method for arsenic (As) removal from groundwater. The impact of seasonal fluctuations in groundwater composition on CFs’ performance has not been passably investigated. The present study assessed the seasonal variability of groundwater quality influencing removal by CFs. Five ceramic filter units made of low-cost ceramic filters and iron netting were installed and monitored in rural households in the Southeastern region of Bangladesh during wet and dry seasons. Raw groundwater and CFs effluents were randomly sampled and analyzed in both seasons. The groundwater redox potential (Eh) and electrical conductivity (EC) decreased by 13–40% and 5–13% in the wet season and shifted toward more reducing conditions. A significant increase of As (20–58%), Fe (13–57%), and P (20–55%) concentrations was observed in the wet season. A strong positive correlation (R2= 0.778) was identified between changing concentrations of As and Fe in both wet and dry seasons. The As, Fe, and P concentration fluctuations were likely associated with changes in the groundwater recharge pattern over the monitoring seasons. Despite the seasonal changes in groundwater composition, the CFs were successful in removing As, Fe, P, and Mn from the groundwater. Higher levels of Fe were required during the wet season, and iron netting was used to ensure the removal of As below the Bangladesh standard limit of 50 µg/L. The low-cost CFs can be implemented in As-affected regions with varying groundwater characteristics to comply with the drinking water demand in rural areas.

Membrane fouling is one of the main factors that hinders the wide application of ultrafiltration (UF) processes. Limited research on the influence of temperature condition on reversible and irreversible natural organic matter (NOM) fouling has been conducted. Fouling and cleaning of a submerged polymeric UF with different NOM components were examined at 5°C, 20°C, and 35°C. Fouling was evaluated using the modified fouling index-UF (MFI-UF) and unified membrane fouling index (UMFI) indices, analysis of cake layer properties, and specific flux recovery. Results showed that fouling increased by 15%–35% when water temperature decreased from 20°C to 5°C, whereas fouling decreased by 15%–25% when the temperature increased to 35°C. The UMFIffouling order was consistent across all temperature conditions with the NOM mixture and bovine serum albumin (BSA) fouling more severely than the alginate and humic acid. The UMFI and MFI-UF exhibited the same fouling order and can be used in complement to each other. BSA was found to be more sensitive to temperature changes and irreversibly fouling more than humic acid and alginate. The ratio of irreversible to reversible fouling (UMFIhir/UMFIhr) increased by 15%–25% from 35°C to 20°C and by 30%– 40% from 20°C to 5°C indicating the need for altered cleaning strategies at cold water 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.

•Water temperature demonstrated impacts on ceramic UF permeability and fouling.•The impact of temperature on fouling was over and beyond simple viscosity changes.•Cold water temperature 5 °C resulted in higher irreversible fouling compared to 20 °C.•At 5 °C condition fouling transitioned from standard to intermediate pore blocking.•Cleaning strategies with NOM impacted water must be altered at cold water condition.