The riverbank filtration (RBF) technique is widely used for drinking water production but may be sensitive to anthropogenic alterations of river systems. We investigated the early response of an RBF system in southern Poland to sustained river impoundment associated with a small hydropower plant (SHP) operation during the first 18 months following its commissioning. High-resolution monitoring integrated with hydrochemical analyses, including pharmaceuticals and personal care products (PPCPs), was applied to assess changes in river–groundwater interactions and water quality. The impoundment was accompanied by higher, more stable groundwater levels and shorter groundwater residence times in wells near the riverbank, and groundwater hydrochemistry suggested a shift towards more reducing conditions within the aquifer. Nitrate and sulphate concentrations decreased by 70–82% and 48–50%, respectively, while ammonium and manganese increased by up to 56%. Groundwater from more distant wells became more similar to river water following impoundment, suggesting an increased contribution of bank filtrate to aquifer recharge. PPCP concentrations increased in production wells, including a previously unaffected one, in which up to 17 PPCPs were detected after the SHP commissioning. These changes, which may indicate reduced system attenuation capacity, coincided with episodic increases in estimated environmental and human health risks. Deterioration of raw water quality was followed by a reduction of about 50% in groundwater abstraction. The results indicate that even small hydrotechnical structures may alter hydraulic conditions and groundwater quality within the adjacent aquifer and should be considered in water resource management and environmental impact assessment.
Oilfield produced water is the largest liquid by-product of hydrocarbon extraction, yet hypersaline brines carrying emulsified oil, colloids and trace metals remain difficult to pretreat, since high chloride levels accelerate electrode passivation and alter coagulant chemistry. In Saudi Arabia, recovery of such water is attractive in view of extreme freshwater scarcity. Batch electrocoagulation with sacrificial aluminium electrodes was therefore evaluated as a pretreatment stage for a laboratory-formulated synthetic hypersaline produced water containing 48,420 mg L−1 of total dissolved solids, 1247 mg L−1 of chemical oxygen demand, 213 mg L−1 of oil and grease and a turbidity of 465 NTU. A Box–Behnken design was applied to current density (5–20 mA cm−2), electrolysis time (10–40 min) and initial pH (5–9), with the removal of chemical oxygen demand, oil and grease, and turbidity as dependent variables. Quadratic regression models yielded coefficients of determination of 0.9965, 0.9994 and 0.9994, and current density was the dominant factor for each output. Operation at 18.6 mA cm−2, 38.5 min and pH 6.2, located in the region of composite desirability of 0.92, gave measured removals of 89.2 ± 0.6% for chemical oxygen demand, 91.8 ± 0.5% for oil and grease and 95.1 ± 0.4% for turbidity, and removals of 90.1% for Ba2+, 88.1% for Sr2+, 95.9% for total Fe and 93.8% for Zn2+. Electrochemical impedance spectroscopy showed a 3.85-fold increase in the charge-transfer resistance of the anode, from 2.14 to 8.23 Ω, after 40 min of operation, accompanied by a decrease in double-layer capacitance from 18.5 to 12.3 μF, which quantifies progressive anodic passivation. X-ray diffraction of the recovered sludge revealed a transition from amorphous aluminium hydroxide to crystalline bayerite and gibbsite, with the crystallinity index rising from 8.2% to 34.6%. At the selected conditions, the specific energy consumption was 2.29 kWh m−3, the anodic current efficiency was 114.6%, the electricity and electrode cost was 0.661 $ m−3, and a mass balance placed dry sludge generation at 0.77–1.14 kg m−3.
Treatment of textile wastewater is challenging because dyes, salts, and organic matter can strongly affect advanced oxidation processes (AOPs). This study evaluated azo-dye decolorization in a 14 L hydrodynamic cavitation (HC) system previously characterized for nanobubble generation, focusing on sodium chloride (NaCl) effects on performance, kinetics, oxidant demand, and operating cost. Hydrogen peroxide (H2O2) and sodium persulfate (PS) were tested at pH 2–7 and oxidant-to-dye ratios of 50:1–230:1. HC was first assessed for Reactive Red 120 (RR120) and Congo Red (CR) in deionized water, while NaCl effects were investigated for RR120 at 2.5 g/L because CR precipitated under acidified saline conditions. In deionized water, RR120 decolorization reached 95% with both oxidants, whereas CR reached 94% with PS and 69% with H2O2. PS remained effective across the pH range, while H2O2 was most effective at pH 2. Concentration profiles showed an initial rapid decrease followed by one or two slower intervals, potentially reflecting reduced oxidant availability, mass-transfer limitations, competition from transformation products, and changing cavitation conditions. NaCl reduced RR120 decolorization under all investigated conditions, especially at pH 5–7, slowing down the initial and intermediate kinetic stages. Under saline conditions, H2O2 generally outperformed PS at equivalent oxidant-to-dye ratios. Screening-level cost analysis showed that PS-based systems were mainly constrained by oxidant cost, whereas H2O2-based systems were more sensitive to treatment time and energy demand. Overall, NaCl affected removal efficiency, kinetics, oxidant selection, dosage requirements, and treatment economics, identifying salinity as a key design parameter for HC treatment of textile wastewater.
Managing arsenic (As) in acidic metallurgical effluents requires both removal from solution and formation of a stable As-bearing solid. At lower As concentrations, however, scorodite (FeAsO4·2H2O) crystallization can be kinetically constrained. This study investigated how Fe source and initial pH govern biogenic scorodite formation by the thermo-acidophilic archaeon Acidianus brierleyi. At 220 mg/L As(III), waste Fe-sludge supported scorodite crystallization at all tested pH values (1.3–2.0), whereas soluble Fe(II) produced no precipitation at pH 1.5 and poorly ordered Fe–As phases at pH 2.0. A clear contrast emerged at pH 1.5: schwertmannite dissolved extensively but achieved only 23% As removal with negligible XRD evidence of crystalline scorodite, whereas jarosite combined moderate Fe release with 91% As removal and clear crystalline scorodite formation. The pattern reversed at pH 2.0: schwertmannite supported crystallization, whereas jarosite persisted with negligible Fe release and As removal. Thus, neither extensive Fe release nor solid-phase persistence alone ensured crystallization. Under their respective selected conditions, schwertmannite formed scorodite at 220 mg/L but not at ≤150 mg/L As(III), whereas jarosite maintained crystallization down to 90 mg/L. Time-resolved structural analyses indicated progressive jarosite dissolution and scorodite precipitation while residual jarosite persisted. Appropriate matching of Fe-source mineralogy and pH can therefore extend biogenic scorodite crystallization toward lower As concentrations.
Night-time water consumption (NWC) – typically used in the Minimum Night Flow (MNF) method for leakage assessment in water distribution networks (WDNs) – is a key but still poorly investigated parameter, especially in relation to the non-residential sector. This study analyses hourly smart-meter data from 44 small-scale service-industry (SI) users located in Northern Italy, each monitored over a one-year period across distinct monitoring campaigns conducted between January 2017 and January 2026. The dataset includes six user categories: shops, offices, catering services, wellness activities, recreational activities, and police stations. A multi-phase methodology is applied to address: (i) NWC characterization across SI categories; (ii) NWC seasonal variability; and (iii) NWC relationship with yearly billed consumption. Overall, results show low average values of NWC (average 2.8 L/user/h), lower than benchmark value of 7.4 L/user/h reported in the technical literature for the non-residential sector. Strong heterogeneity is observed across categories, with shops and offices exhibiting negligible consumption, whereas catering services show higher and more variable NWC. Seasonal effects are also observed, with higher NWC in warmer months for most users. A statistically significant correlation is found between yearly billed consumption and NWC, indicating the possibility of predicting NWC based only on billing data in the absence of category information. By providing insights into category-specific NWC and individual user's behaviours, the findings can support an improved MNF-based leakage assessment.
