Powdered activated carbon (PAC) is a promising technology to reduce organic micropollutants (OMPs) in drinking water treatment plants and combined with biological treatment processes such as rapid sand filters (RSFs), has the potential to remove a broad range of OMPs during water treatment. However, the removal of OMPs by a combination of two treatments (PAC-RSF) is not fully understood. 49 OMPs were spiked in PAC followed by RSF pilot plant treatment and the effluent was measured after 1, 4 and 7 day(s). Also, in a separate experiment 29 OMPs (out of 49) were dosed into the RSF column to assess the removal of OMPs by just RSF. Statistical analyses were performed and the OMPs were classified according to their charge and hydrophobicity. The results showed that OMPs were removed at the highest percentage after the first 24 h of dosing. The highest removal was observed for the neutral and hydrophobic compounds (80.0%–99.5%). The removal of neutral and hydrophilic compounds varied (0.14%–98.5%) depending on the possibility of forming π-π interactions and hydrogen bonds. Electrostatic repulsion between anionic OMPs and negatively charged PAC led to a decrease in the removal of anionic compounds. In contrast, electrostatic attraction led to an increase in the removal of cationic OMPs. Regarding OMPs removal by RSF, some compounds were removed by the sand filter depending partly on their physical-chemical properties and more dominantly on their functional groups. By comparing the OMPs removal by PAC-RSF with RSF, it was possible to determine the contribution of biological processes in the sand filter in the removal of some OMPs.

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Reverse osmosis (RO) is the most promising membrane technology in organic micropollutants (MPs) removal of drinking water treatment. For 78 MPs, passage and removal were evaluated with an ESPA3 RO membrane and the robustness of RO against MPs was studied. The MPs were classified according to their charge and hydrophobicity. The results showed that the size of neutral compounds was negatively correlated with their passage. This correlation was weaker for neutral hydrophobic MPs than neutral hydrophilic MPs. The lowest passage (0.2%–4%) was displayed by anionic MPs because of electrostatic repulsion between the negatively charged solute and negatively charged membrane surface. Cationic MPs showed a higher passage (around 0.4%–40%) due to electrostatic sorption and Donnan exclusion. The relationship between physical-chemical properties of MPs and their passage was evaluated by the one-way analysis of variance (ANOVA). We performed a qualitative analysis of variables using Principal Component Analysis (PCA) in order to examine the physical-chemical properties of compounds that affect the membrane removal of MPs. After analysis with Multiple Linear Regression (MLR), we concluded that properties such as molecular width, equivalent molecular width, pKa and solubility can be considered as significant descriptors for prediction of the membrane removal. The influence of feed water temperature on MPs passage was also assessed. The results revealed that a rise of water temperature from 5 to 19 °C, increases the average passage of MPs by 6.5%.@en

Groundwater monitoring and pumping wells set in anoxic aquifers require attention to keep the groundwater free of dissolved oxygen (DO). In properly constructed monitoring or pumping wells, two processes can however still introduce oxygen to anoxic groundwater: (1) permeation of oxygen through polymer materials such as silicone, PVC, HDPE or Teflon, and (2) thermally driven convection, which can occur in all types of piezometers or wells, regardless of construction material, when the water table or pressure head is close (

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Recent studies have indicated that wastewater contains relatively large amounts of thermal energy. Recovering this thermal energy can be used to decrease the CO2 footprint of the water cycle. This paper describes the development of a model to simulate the heat balance and predict the temperature in a sewer system. The model can be used to estimate the recoverable thermal energy and its dynamics. The model was verified with field data. It was concluded that the model is a powerful and accurate tool to simulate the heat balance of a sewer system at the urban district level. It was found that the recoverable heat show highly dynamic patterns, directly related to water consumption patterns. The recoverable heat depends on technical aspects as well as regulations for maximum acceptable temperature differences due to heat abstraction.@en