Removal In Water Treatment Plants Research Articles

An Overview of the Progress made in Research on Odor Removal in Water Treatment Plants

Odor is one of the most intuitive indicators for assessing drinking water quality in waterworks. Removing odors is of great importance to improve the quality of tap water, ensure people’s health, and address public perception. The effective identification of odors in drinking water and the exploration of the source of the odor are the prerequisites for eliminating odors. Therefore, this article first discusses the sources and types of odors that are typical in current drinking water, focuses on reviewing the research progress of odor removal technologies in water treatment plants, including adsorption technology, chemical oxidation technology, biodegradation technology and combined technology, and explains the advantages, disadvantages, principles, research progress, practical application scenarios, considerations and application prospects of each odor-removal technology. It is expected to provide a reference for controlling odor pollution in drinking water.

Biotransformation and detoxification of saxitoxin by Bacillus flexus in batch experiments.

Saxitoxins (STXs) are carbamate alkaloid neurotoxins produced by some species of cyanobacteria. They are water soluble and relatively stable in the natural environment, and thereby represent a risk to animal and human health through a long-time exposure. STXs cannot be sufficiently removed by conventional water treatment methods. Therefore, this study investigates the potential STX biodegradation and detoxification by bacteria as a promising method for toxin removal. STX biodegradation experiments were conducted using Bacillus flexus SSZ01 strain in batch cultures. The results revealed that SSZ01 strain grew well and rapidly detoxified STX, with no lag phase observed. STX detoxification by SSZ01 strain was initial-toxin-concentration-dependent. The highest biotransformation rate (10µg STX L-1day-1) the pseudo-first-order kinetic constant (0.58 d-1) were obtained at the highest initial toxin concentration (50µg L-1) and the lowest ones (0.06µg STX L-1day-1 and 0.14 d-1, respectively) were recorded at the lowest initial concentration (0.5µg L-1). STX biotransformation rate increased with temperature, with highest occurred at 30ºC. This rate was also influenced by pH, with highest obtained at pH8 and lowest at higher and lower pH values. HPLC chromatograms showed that STX biotransformation peak is corresponding to the least toxic STX analog (disulfated sulfocarbamoyl-C1 variant). The Artemia-based toxicity assay revealed that this biotransformation byproduct was nontoxic. This suggests the potential application of this bacterial strain in slow sand filters for cyanotoxin removal in water treatment plants. Being nontoxic, this byproduct needs to be assayed for its therapeutic effects toward neurodegenerative diseases.

PARAFAC model as an innovative tool for monitoring natural organic matter removal in water treatment plants.

The increase of fluorescent natural organic matter (fNOM) fractions during drinking water treatment might lead to an increased coagulant dose and filter clogging, and can be a precursor for disinfection by-products. Consequently, efficient fNOM removal is essential, for which characterisation of fNOM fractions is crucial. This study aims to develop a robust monitoring tool for assessing fNOM fractions across water treatment processes. To achieve this, water samples were collected from six South African water treatment plants (WTPs) during winter and summer, and two plants in Belgium during spring. The removal of fNOM was monitored by assessing fluorescence excitation-emission matrices datasets using parallel factor analysis. The removal of fNOM during summer for South African WTPs was in the range 69-85%, and decreased to 42-64% in winter. In Belgian WTPs, fNOM removal was in the range 74-78%. Principal component analysis revealed a positive correlation between total fluorescence and total organic carbon (TOC). However, TOC had an insignificant contribution to the factors affecting fNOM removal. Overall, the study demonstrated the appearance of fNOM in the final chlorinated water, indicating that fNOM requires a customised monitoring technique.

Molecular surveillance of human rotaviruses in drinking water and investigation of the efficiency of their removal in Isfahan water treatment plant.

Enteric viruses, especially human rotaviruses present in aquatic environments, are microbial criteria in quality assessment of water resources. The present research aimed to investigate molecular monitoring of human rotavirus and efficacy evaluation of Isfahan water treatment plant (WTP) in the elimination of viruses. In total, 60 water samples were collected from different units of WTP. Zeta plus electropositive Virosorb cartridge filter and elution buffer was used for concentrating water samples. Enzyme-linked immunosorbent assay (ELISA) was used for detecting rotavirus antigen. Quantitative real-time reverse transcription PCR (qRT-PCR) with SYBR Green I fluorescent dye was performed for molecular detection of rotavirus. Multiplex nested reverse transcription-polymerase chain reaction (RT-PCR) was used for rotavirus G genotyping. Total coliform count varies from 102-103 CFU/mL in the raw water resources. Rotavirus antigen was detected in 17 samples (28.33%) by ELISA, and 13 samples (21.67%) were found positive by RT-PCR. These included 41.18% (7 cases) of raw water influent, 29.41% (5 cases) after sedimentation, 23.52% (4 cases) after ozonation, and 5.88% (1 case) after filtration in ELISA method. The highest number of rotaviruses was detected by qRT-PCR in autumn (46.15% (6 cases)). The commonest circulating G type in the sampling points was the mixed types, which was identified in 6 samples (46.15%), followed by non-typeable (23.07%), G3 (15.38%), G1 (7.69%), and G8 (7.69%), respectively. Despite the presence of rotavirus in raw water, after clarification and ozonation, filtration and treated water did not show the presence of rotavirus. The results of this study showed that multi-stage treatment has a positive effect on virus removal in WTP.

Effect of container geometry on colloids removal from water in oscillation-based flocculation

Abstract Colloid removal in water treatment plants is commonly done by a sequence of processes that includes coagulation, flocculation, sedimentation, and filtration. The current study presents an innovative technique, termed grouping, for the removal of these suspended particles based on physical flow manipulation, which causes the particles to aggregate. Previous results showed that gentle oscillation in a cylindrical container facilitates simultaneous flocculation and sedimentation in the same reactor over shorter periods of time than are possible using the conventional treatment approach. This finding may confer marked improvements on the processes used today by enabling the use of both smaller reactors and less energy. Based on the findings with the cylindrical vessel, here the grouping technique is further examined in a rectangular container and over a range of different initial turbidities. The results indicate that the removal efficiency is higher in the rectangular container under the different initial turbidities tested. In addition, the removal efficiency was shown to remain robust with the decreases in initial turbidity and alum concentrations that occur during treatment. The positive results of our previous study taken together with this finding hint at the strong potential of the grouping technique to improve common flocculation processes.

Manganese-oxidizing bacteria isolated from natural and technical systems remove cylindrospermopsin

The cyanotoxin cylindrospermopsin was discovered during a drinking water-related outbreak of human poisoning in 1979. Knowledge about the degradation of cylindrospermopsin in waterbodies is limited. So far, only few cylindrospermopsin-removing bacteria have been described. Manganese-oxidizing bacteria remove a variety of organic compounds. However, this has not been assessed for cyanotoxins yet. We investigated cylindrospermopsin removal by manganese-oxidizing bacteria, isolated from natural and technical systems. Cylindrospermopsin removal was evaluated under different conditions. We analysed the correlation between the amount of oxidized manganese and the cylindrospermopsin removal, as well as the removal of cylindrospermopsin by sterile biogenic oxides. Removal rates in the range of 0.4–37.0 μg L−1 day−1 were observed. When MnCO3 was in the media Pseudomonas sp. OF001 removed ∼100% of cylindrospermopsin in 3 days, Comamonadaceae bacterium A210 removed ∼100% within 14 days, and Ideonella sp. A288 and A226 removed 65% and 80% within 28 days, respectively. In the absence of Mn2+, strain A288 did not remove cylindrospermopsin, while the other strains removed 5–16%. The amount of manganese oxidized by the strains during the experiment did not correlate with the amount of cylindrospermopsin removed. However, the mere oxidation of Mn2+ was indispensable for cylindrospermopsin removal. Cylindrospermopsin removal ranging from 0 to 24% by sterile biogenic oxides was observed. Considering the efficient removal of cylindrospermopsin by the tested strains, manganese-oxidizing bacteria might play an important role in cylindrospermopsin removal in the environment. Besides, manganese-oxidizing bacteria could be promising candidates for biotechnological applications for cylindrospermopsin removal in water treatment plants.

Removal of Natural Organic Matter (NOM), Turbidity, and Color of Surface Water by Integration of Enhanced Coagulation Process and Direct Filtration

This work assesses the efficiency of integrated enhanced coagulation and direct filtration processes for the removal of color, turbidity, and natural organic matter (NOM) from surface water. The processes were conducted in a simulated pilot. The operating conditions of the treatment process, including pH, FeCl3 dose, and influent flow, were investigated. Following that, its efficiency was evaluated by measuring specific water quality parameters in the output stream including NOM, turbidity, and color. The results showed that under optimum conditions (pH, FeCl3 dose, and influent flow of 6.2, 95 L/h, and 40 mg/l, respectively), the color and turbidity were removed 96% and 95% respectively. According to factors analysis by the Taguchi method, the influence of these factors on the removal of pollutants decreased as follows: pH → FeCl3 dose → influent flow. The results revealed that the integrated enhanced coagulation process and direct filtration can improve the efficiency of colors, turbidity, and NOM removal in water treatment plants.

A review on bisphenol A occurrences, health effects and treatment process via membrane technology for drinking water.

Massive utilization of bisphenol A (BPA) in the industrial production of polycarbonate plastics has led to the occurrence of this compound (at μg/L to ng/L level) in the water treatment plant. Nowadays, the presence of BPA in drinking water sources is a major concern among society because BPA is one of the endocrine disruption compounds (EDCs) that can cause hazard to human health even at extremely low concentration level. Parallel to these issues, membrane technology has emerged as the most feasible treatment process to eliminate this recalcitrant contaminant via physical separation mechanism. This paper reviews the occurrences and effects of BPA toward living organisms as well as the application of membrane technology for their removal in water treatment plant. The potential applications of using polymeric membranes for BPA removal are also discussed. Literature revealed that modifying membrane surface using blending approach is the simple yet effective method to improve membrane properties with respect to BPA removal without compromising water permeability. The regeneration process helps in maintaining the performances of membrane at desired level. The application of large-scale membrane process in treatment plant shows the feasibility of the technology for removing BPA and possible future prospect in water treatment process.

Impact of kaolinite clay particles on the filtration of Cryptosporidium-sized microspheres

Granular filtration remains a key barrier for Cryptosporidium removal in water treatment plants without UV irradiation. To assess the impact of clay particles in source water on Cryptosporidium removal efficiency by granular filtration, this study investigated the co-transport of Cryptosporidium-sized microspheres and kaolinite particles in sand columns. To investigate the influence of clay load on microsphere transport and deposition, varying influent kaolinite concentrations (0–106particles/mL) and microsphere concentrations (102–106microspheres/mL) were tested. The spatial distribution of retained microspheres was examined subsequent to experiments via filter coring. Results demonstrate that increasing the influent microsphere concentration impaired filter performance due to a blocking mechanism whereby previously retained particles repel incoming particles. In contrast, when the particulate load was dominated by kaolinite (for an equivalent particulate load), filter performance improved as a result of filter ripening whereby previously deposited particles act as additional collectors. Thus, microsphere-kaolinite interactions proved to be favorable although both particles possessed negative zeta potentials in the tested conditions. This study demonstrates that granular filter performance is vulnerable to peak events of microbial contamination. Conversely, Cryptosporidium-sized microsphere removal by granular filtration is enhanced in the presence of kaolinite in source water.

On the concept of the future drinking water treatment plant: algae harvesting from the algal biomass for biodiesel production—a review

Abstract It is well established that the drinking water treatment has several disadvantages such as it may rupture the algae, thereby releasing the taste- and odour-producing oils before the whole algae are removed from the treatment system. This review aims to present the concept of algae recovery instead of its removal in drinking water treatment plant. Control of algae in water supplies and some coagulation/flocculation and electrolysis experiments as harvesting methods are discussed. In fact, algae recovery instead of its removal in water treatment plant is a promising perspective and a suitable issue when the surface water comes from dams where algae blooms occur frequently. Micro-algae are a sustainable energy resource with great potential for CO2 fixation. The micro-algae could be grown in photo-bioreactors or in open ponds. A new interesting field of research would be fast and simultaneous algal biodiesel production with drinking water treatment in the biodiesel production/water treatment plant wi...

Brazilian Bentonites for Geosynthetic Clay Liners (GCL)

Bentonites have been used for several purposes, due to their excellent physical, chemical, and structural properties. The main applications of bentonites in Brazil are, among others, as agglomerants for foundry molds, in iron ore pelletizing, as drilling mud in oil and water wells, as wine clarifiers, in catalysis, at the chemical and pharmaceutical industries, for pollutants removal in water treatment plants, and in cosmetics. Since the 1980’s, bentonites have been used as barriers in landfills, thanks to the attractive characteristics of the montmorillonite, the principal clay mineral in the smectitic clays (popularly called bentonites). The inadequate accumulation of residues in soils and waters is identified as one of the most serious current problems. Nowadays, geosynthetic clay liners, or GCL’s, have been used as a geo-synthetic hydraulic barrier. They are constituted by a sodium or calcium bentonite layer encapsulated in geo-textiles or attached to geo-membranes, which are secured together by physical or chemical methods. This paper discusses GCL’s, their uses, the influences of the type of clay, the working principles, the related aspects to landfills projects, and also the main Brazil’s bentonite exploitation areas.

Practical selection of microorganisms indicating the stability of pathogenic removal in water treatment plants

There have been several recent drinking water incidents in connection with detection of water borne pathogens in Korea. This has led to the need for research to find microorganisms that will indicate the stability of pathogenic removal in water treatment plants (WTPs). We investigated seven microorganisms as potential indicators: four for bacteria [E. coli, fecal coliform (FC), total coliform (TC) and heterotrophic plate counts (HPC)], two for protozoan [aerobic spore formers (ASF) and Clostridium perfringens (CP) spore], and one for viruses (F-specific RNA coliphage). Source water, treated water from each process, and finished water were analyzed periodically from three WTPs, chosen in view of the source water quality and plant size. This study concludes that HPC and ASF appeared to be good indicators of the stability of pathogenic removal. Although this study supports ASF as the best indicating microorganism, the potential use of HPC as an indicating microorganism was demonstrated in this study. From this study, the regrowth problem of HPC in water plants was shown to be negligible depending on the characteristics of the chlorination practice at the WTPs, and temperate climate conditions. The relative importances of each treatment process, for the removal of suggested indicating microorganisms, were found to be as follows: combined process of coagulation and sedimentation with prechlorination > filtration » disinfection, with emphasis on the necessity for the optimization of whole water treatment processes for effective microbial removal.

Bacteriophage removal in water treatment plants

Presence of bacteriophages was evaluated at different stages of two water treatment plants in order to investigate the usefulness of phages as model organisms for assessing the efficiency of the processes. Bacteriophages tested were somatic coliphages, F-specific coliphages and phages infecting Bacteroides fragilis. The presence of human enteric viruses was determined as well in the raw water, the finished water and in samples taken in the distribution network. Results show that in these particular treatment plants, which include prechlorination, phages infecting B. fragilis are more resistant to the treatment processes than the other two phages studied.

Bacteriophage removal in water treatment plants

Presence of bacteriophages was evaluated at different stages of two water treatment plants in order to investigate the usefulness of phages as model organisms for assessing the efficiency of the processes. Bacteriophages tested were somatic coliphages, F-specific coliphages and phages infecting Bacteroides fragilis. The presence of human enteric viruses was determined as well in the raw water, the finished water and in samples taken in the distribution network. Results show that in these particular treatment plants, which include prechlorination, phages infecting B. fragilis are more resistant to the treatment processes than the other two phages studied.