Water Treatment Processes For Removal Research Articles

Removal of micron-sized microplastic particles from simulated drinking water via alum coagulation

Microplastics are being recognized as an emerging pollutant entering wastewater and drinking water treatment plants. Microplastics are often defined as having a dimension less than 5 mm, however much smaller plastic particles have been identified in the environment. While a few studies have addressed the effectiveness of traditional water treatment processes for the removal of microplastics in the mm-size range, additional investigations that study the behavior of smaller plastic particles during water treatment are needed. The results of this work confirm that conditions which are suitable for the removal of a conventional oxide colloid, kaolin, are also effective for the removal of a model plastic sphere (density 1.3 g/cm3, 1–5 µm diameter). Coagulation using alum at concentrations between 5 and 10 mg/L Al produced water with turbidity less than 1.0 NTU from solutions containing 5 mg/L microspheres with an initial turbidity of 16 NTU. Although the presence of 20 mg/L of surfactant in solution shifted the microsphere zeta potential, it did not impair microsphere coagulation at low alum doses and all solutions showed a gradual trend toward higher residual NTU at higher alum dose. Evidence from floc photos and zeta potential measurements point to sweep flocculation as the dominant mechanism for microsphere removal for the conditions of this study. The dispersion of polyethylene microfibers (density 0.96 g/cm3, 5 µm diameter cut to 0.1 mm lengths) in water was strongly influenced by surfactants yet the fibers were still effectively removed via coagulation. Further experimentation with other plastics and solution conditions is needed to enhance understanding of the effectiveness of traditional water treatment processes for microplastic removal.

Abundance and removal of antibiotic resistance genes (ARGs) in the rearing environments of intensive shrimp aquaculture in South China

Although research regarding antibiotic resistance genes (ARGs) in aquaculture environments has gained increasing scientific interest, further studies are required to understand the abundances and removal mechanisms of ARGs during the entire rearing period of shrimp aquaculture. Thus, in this study, abundances, distributions and removal rates of ARGs in different environmental compartments of intensive shrimp farms in South China were investigated during the entire rearing period. The results indicated that sul1 and cmlA were the predominant ARGs in the water and sediment samples. Additionally, the total abundance of ARGs was higher in shrimp pond water than in the source water and farm effluent. Moreover, sediment samples indicated significantly higher ARG abundances than water samples from the shrimp ponds (P < 0.05). Environmental factors were found to significantly affect the distribution of ARGs in shrimp rearing environments. Furthermore, stable ponds aided the removal of ARGs from shrimp pond water. This study accounted for temporal variations in ARG abundances as well as removal of ARGs in different environmental compartments during the entire shrimp rearing period. However, additional research is required to optimize the water treatment process for removal of ARGs from the aquaculture.

In vitro bioassays to evaluate complex chemical mixtures in recycled water

With burgeoning population and diminishing availability of freshwater resources, the world continues to expand the use of alternative water resources for drinking, and the quality of these sources has been a great concern for the public as well as public health professionals. In vitro bioassays are increasingly being used to enable rapid, relatively inexpensive toxicity screening that can be used in conjunction with analytical chemistry data to evaluate water quality and the effectiveness of water treatment. In this study, a comprehensive bioassay battery consisting of 36 bioassays covering 18 biological endpoints was applied to screen the bioactivity of waters of varying qualities with parallel treatments. Samples include wastewater effluent, ultraviolet light (UV) and/or ozone advanced oxidation processed (AOP) recycled water, and infiltrated recycled groundwater. Based on assay sensitivity and detection frequency in the samples, several endpoints were highlighted in the battery, including assays for genotoxicity, mutagenicity, estrogenic activity, glucocorticoid activity, arylhydrocarbon receptor activity, oxidative stress response, and cytotoxicity. Attenuation of bioactivity was found to be dependent on the treatment process and bioassay endpoint. For instance, ozone technology significantly removed oxidative stress activity, while UV based technologies were most efficient for the attenuation of glucocorticoid activity. Chlorination partially attenuated genotoxicity and greatly decreased herbicidal activity, while groundwater infiltration efficiently attenuated most of the evaluated bioactivity with the exception of genotoxicity. In some cases, bioactivity (e.g., mutagenicity, genotoxicity, and arylhydrocarbon receptor) increased following water treatment, indicating that transformation products of water treatment may be a concern. Furthermore, several types of bioassays with the same endpoint were compared in this study, which could help guide the selection of optimized methods in future studies. Overall, this research indicates that a battery of bioassays can be used to support decision-making on the application of advanced water treatment processes for removal of bioactivity.

An integrated radiation-microbiological water treatment process for removal of petroleum products

The possibility of using an integrated approach to water purification for the removal of petroleum products on the basis of the reagent-free “green chemistry” processes of radiation treatment and biodegradation has been explored. The treatment of water containing diesel fuel, engine oil, and fuel oil has shown that these processes hold much promise. The radiation treatment has led to a twelvefold reduction in COD, with the BOD values increasing with an increase in the radiation dose, thereby suggesting that recalcitrant molecules are decomposed to simpler ones amenable to bio-oxidation. It has been found that the maximum percentage of biodegradation is achieved for the solutions irradiated to maximal doses, although the efficiency of biodegradation increases by more than a factor of 2 after irradiation to 5 kGy because of the destruction of hardly biodegradable compounds. Thus, it has been proposed to increase the petroleum product removal efficiency in water purification by employing the integrated radiation-microbiological process comprising the use of ionizing radiation for the formation of a precipitate and the decomposition of the petroleum products into lighter fragments in the first purification step and subsequently removing the latter from the water by the biological method.

Magnetic solid–liquid extraction of Eu(III), La(III), Ni(II) and Co(II) with maghemite nanoparticles

Magnetic nanoparticles (maghemite γ-Fe2O3) functionalised with citrate ions were synthesised and characterised. These highly dispersible particles are stable in aqueous media and have a large surface area (170m2g−1), which confers them a high number of active sites leading to a large ion loading capacity. The adsorption of Eu3+, La3+, Co2+ and Ni2+ ions from aqueous solution by these citrate-coated magnetic nanoparticles was studied. The maximum adsorption capacities determined by fitting experimental data with Langmuir model were close to 0.5mmolg−1 for the 4 cations studied. The kinetic study showed a rapid adsorption due to the presence of active sites on the external surface of the magnetic nanoparticles. The equilibrium time is 15min at most and at least 83% of cations are adsorbed after 1min. The effect of pH was also investigated. The adsorbed amount of cations increases drastically with pH from pH 2 to 3.5 and remains constant over pH 3.5. In addition, competitive adsorption was investigated. The adsorption capacity of the citrate-coated magnetic nanoparticles for both cations together (Eu3+/La3+ or Co2+/Ni2+) is similar to those obtained when each type of ion was present alone. These results show that these nanoparticles could be used in water treatment process for removal of pollutants. Indeed, this magnetic adsorbent is efficient and easily removed from the aqueous solution by applying a magnetic field.

The effectiveness of water treatment processes for removal of herbicides

A number of water treatment processes have been investigated for their efficiencies in removing certain herbicides from freshwater samples. The herbicides used were the chlorphenoxy acids MCPA and mecoprop and the carbamates, isoproturon, linuron and chlortoluron, as these are used abundantly in Grampian Region and therefore are a potential source of contamination of potable water supplies in the region. Laboratory-based simulations of filtration treatment were set up using a number of types of activated carbon, sand, clay and peat. The results that certain types of activated carbon are very effective for removal of these herbicides from freshwaters. Clay and peat are also effective in removing the herbicides, but sand filtration proved ineffective.