Geosmin and 2-methylisoborneol (MIB) are the most common causes of unpleasant odours in drinking water. A method was proposed to detect and recognise these compounds in water and determine their concentrations. The method utilises commercial solid-state gas sensors and data analysis. Sample preparation plays an important role. The aqueous solution is converted into a gas sample using a specially designed dynamic headspace. The responses of the sensors are recorded during exposure to headspace vapours in a dynamic mode. The best limit of detection for geosmin, LOD = 6.20 µg/L, was attained with a TGS2602 sensor. The best limit of detection for MIB, LOD = 0.52 µg/L, was attained with a TGS826 sensor. Geosmin and MIB recognition was 100% successful based on TGS826 and TGS2602 response classifications. Geosmin and MIB concentrations were effectively determined in solutions containing one or both compounds. The respective mathematical models utilised the responses of TGS826 and TGS2602. The smallest concentration prediction error was RMSE = 2.19 µg/L (for geosmin) and RMSE = 0.33 µg/L (for MIB). The study demonstrated the application potential of non-specific gas sensors for the early warning monitoring of geosmin and MIB presence in water. Further studies are needed to develop a system that can be tested in field conditions.

The necessity of rational water resource management and reduction of water consumption demandsthat water utilities address water losses during water treatment. Therefore, the backwash water generated during the filtration process is often the focus of research aimed at its reuse within the water treatment system. The studies outlined here were conducted in a large water treatment plant (100,000 m3), focusing on the backwash water produced from sand bed filter flushing. Prior to its reintroduction into the treatment train, the backwash water underwent pre-treatment using ultrafiltration (UF) process with two different modules: a spiral module with a PVFD (200kDa) membrane and a capillary module with a PES (80kDa) membrane. The effectiveness of the process was evaluated based on the degree of retention of organic substances and microorganisms, which pose health risks in backwash water recirculation. The capillary membrane exhibited greater effectiveness in retaining these contaminants, thereby ensuring the complete elimination of pathogenic microorganisms. The study findings indicate that pre-treating backwash water using UF membranes and reintroducing it into the water treatment system before the ozonation process can lead to a reduction of environmental fees. However, this process results in a 1.5% increase in water treatment costs

The growing water deficit around the world contributes to the need to reduce water losses and implement a circular economy. This is the main reason for searching for additional water sources or limiting water losses. In the case of water supply companies, apart from water losses in the distribution system, the greatest amounts of water are used for filter backwashing.The returning of backwash to the drinking water system can be suitable method for recycling of 3–10% of water treated in water treatment plants (WTPs), but high levels of backwash pollution make pretreatment necessary prior to recirculation. Backwash from surface and infiltration water treatment plants is characterized by different level of pollution and types of contaminants, except for microorganisms, which are present in both backwash types. The aim of this study was to evaluate the effectiveness of coagulation as a method of pre-treating backwash before recirculation to the main water treatment system. Prehydrolized coagulant is characterized by a higher removal efficiency for all pollutants, which allows the use of smaller doses. Optimal doses were 5 mg/L and 7 mg/L for PAX XL3 and ALS coagulants respectively. Independent of doses and type of coagulants, coagulation and sedimentation processes did not provide enough efficiency of microorganism removal. The results of this study have found that it is necessary to include other processes, especially disinfection, for pre-treating backwash prior to recirculating it to the treatment system. On the other hand, the cost of backwash recirculation is higher than the cost of intake water.

Tests of microfiltration efficiency used for the pretreatment of backwash water from sand filters were conducted at two water treatment plants treating surface water and infiltration water. Microfiltration efficiency was evaluated for three membrane modules: two with polymeric membranes and one with a ceramic membrane. This study showed that the contaminants that limit the reuse of backwash water from both plants by returning them to the water treatment line are mostly microorganisms, including pathogenic species (Clostridium perfringens). Additionally, in the case of backwash water from infiltration water treatment, iron and manganese compounds also had to be removed before its recirculation to the water treatment system. Unexpectedly, organic carbon concentrations in both types of backwash water were similar to those present in intake waters. Microfiltration provided for the removal of organic matter, ranging from 19.9% to 44.5% and from 7.2% to 53.9% for backwash water from the treatments of surface water and infiltration water, respectively. Furthermore, the efficiency of the iron removal from backwash water from infiltration water treatment was sufficient to ensure good intake water quality. On the other hand, manganese concentrations in the backwash water, from infiltration water treatment, pretreated using the microfiltration process exceeded the levels found in the intake water and were, therefore, an additional limiting factor for the reuse of the backwash water. In both types of backwash water, the number of microorganisms, including Clostridium perfringens (a pathogenic one), was a limiting parameter for backwash water reuse without pretreatment. The results of the present study showed the possibility for using microfiltration for the pretreatment of backwash water, regardless of its origin but not as the sole process. More complex technological systems are needed before recirculating backwash water into the water treatment system. The polyvinylidene fluoride (PVDF) membrane proved to be the most effective for DOC and microorganism removal from backwash water.

Microfiltration membranes are widely used in drinking water treatment due to their high efficiency. However, long-term operation of polymeric membranes may lead to deterioration of hydraulic properties as a result of fouling and material aging. This study aims to determine the impact of long-term aging on hydraulic permeability and separation properties, and to determine the lifespan of microfiltration polyvinylidene fluoride (PVDF) membranes. The practical and industrial novelty of this study lies in providing an authentic, 11-year operational baseline for a full-scale microfiltration system treating highly variable surface water. The study evaluates membranes installed in a full-scale plant in Jarosław (Poland), treating surface water from the San River. The system includes 120 PVDF capillary modules (0.1 μm). After 11 years, the membranes maintained very high separation efficiency, ensuring almost complete removal of turbidity and microorganisms. However, membrane resistance increased nearly threefold, while permeability decreased by about 86%. Maintaining capacity required a gradual increase in transmembrane pressure. The permeability loss exceeded the commonly accepted replacement threshold of 70%, suggesting that membrane replacement after more than a decade of operation is technically and economically justified.