T.C., Prathna; Sharma, Saroj Kumar; Kennedy, Maria. Review: Nanoparticles in household level water treatment: An overview Separation and Purification Technology 30 June 2018 199:260-270
Providing safe drinking water is a great challenge for both the developing and the developed world. Increasing demand and source water quality deterioration has led to the exploration of new technological innovations for better water management. Nanotechnology holds great promise in ensuring safe drinking water through designing innovative centralised and decentralised (household-level) water treatment systems. The paper provides an overview of recent advances in nanotechnologies for (household level) water treatment processes, such as its use as nanoadsorbents, photocatalysts, microbial disinfectants and in membranes. Extensive implementation of nanotechnology for water treatment would require overcoming the high cost of the nanomaterials by enabling their reuse and regeneration. This would also ensure minimising potential environmental exposure. Potential advances in nanotechnology must go hand in hand with environmental health to alleviate any undesirable consequences to humans.
Dhadge VL, Medhi CR, Changmai M, Purkait MK. House hold unit for the treatment of fluoride, iron, arsenic and microorganism contaminated drinking water. Chemosphere 2018 Feb 16;199:728-736. doi: 10.1016/j.chemosphere.2018.02.087.
A first of its kind hybrid electrocoagulation-filtration prototype unit was fabricated for the removal of fluoride, iron, arsenic and microorganisms contaminated drinking water. The unit comprised of 3 chambers, chamber A consisting of an inlet for the water to be treated and an outlet for the treated water along with one block of aluminum electrodes. Chamber B consisted of ceramic membrane filtration assembly at the bottom over a metallic support which filters the flocs so produced in chamber A and chamber C consisting of space to collect the treated water. Operating parameters were maintained as current density of 625 A m-2 and an electrode distance of 0.005 m. Contaminated drinking water containing mixture of fluoride (10 mg L-1), iron (25 mg L-1), arsenic (200 μg L-1) and microorganisms (35 CFU ml-1) was used for the experiment. A removal of 98.74%, 95.65%, 93.2% and 100% were obtained for iron, arsenic, fluoride and microorganisms, respectively. The apparatus and method made it possible to efficiently treat contaminated drinking water to produce drinkable water as per WHO specification. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDX and XRD and explained.
Shivaraju HP, Egumbo H, Madhusudan P, Kumar KMA, Midhun G. Preparation of Affordable and Multi-functional Clay-based Ceramic Filter Matrix for Treatment of Drinking Water. Environmental technology. 2018 Jan 18:1-30. doi: 10.1080/09593330.2018.1430853.
In the present study, affordable clay-based ceramic filters with multi-functional properties were prepared using low-cost and active ingredients. The characterization results of as-prepared materials clearly revealed well crystallinity, structural elucidation, extensive porosity, higher surface area, higher stability, and durability which apparently enhance the treatment efficiency. The filtration rates of ceramic filter were evaluated under gravity and the results obtained were compared with typical gravity slow sand filter. All ceramic filters showed significant filtration rates of about 50-180 m/h, which is comparatively higher than typical slow sand filter. Further, purification efficiency of clay-based ceramic filters was evaluated by considering important drinking water parameters and contaminants. A significant removal potential was achieved by clay-based ceramic filter with 25 and 30 % activated carbon (AC) along with active agents. Desired drinking water quality parameters were achieved by potential removal of nitrite (98.5 %), nitrate (80.5 %), total dissolved solids (62 %), total hardness (55 %), total organic pollutants (89 %), and pathogenic microorganisms (100 %) using ceramic filters within short duration. The remarkable purification and disinfection efficiencies were attributed to the extensive porosity (0.202 cm3g-1), surface area (124.61 m2g-1), stability and presence of active nanoparticles such as Cu, TiO2, and Ag within porous matrix of ceramic filter. The low cost clay-based ceramic filter was found to be easily reusable, handy, durable, and effective for the treatment of drinking water at household level.
Hill L, Suursoo S, Kiisk M, Jantsikene A, Nilb N, Munter R, Realo E, Koch R, Putk K, Leier M, Vaasma T, Isakar K. Long-term monitoring of water treatment technology designed for radium removal-removal efficiencies and NORM formation. J Radiol Prot. 2017 Dec 6;38(1):1-24. doi: 10.1088/1361-6498/aa97f2.
A drinking water treatment plant in Viimsi, Estonia, was monitored over three years for iron, manganese, radium-226, radium-228, as well as their daughter nuclides, in order to determine the efficiency of the treatment process, gain an insight into the removal mechanisms and interactions between radium, iron, and manganese, and assess the overall longevity and performance of the technology along with the possible build-up of NORM in the treatment process. During the study, samples were collected from raw water, first and second stage filtrate, consumer water, backwash water and filter materials. The results show consistent removal efficiency for iron and manganese, as well as an average of over 85% removal for radium with a slight decline over time. The backwash process has been optimised for maximum radium removal from the filters, while keeping concentrations in the backwash water below exemption levels. However, the accumulation of radium and thorium occurs in the filter material, exceeding exemption levels in the top layer of the filter columns in less than a year. By the end of the observation period, activity concentrations in the top layer of the columns were above 30 000 Bq kg-1 for Ra-226 and Ra-228, and around 15 000 Bq kg-1 for Th-228. Radionuclides are not homogenously distributed in the filter columns. In order to estimate the average activity concentrations in the filter media, the height distribution of radionuclides has to be accounted for. Two years and two months after commissioning the treatment plant, the average activity concentrations of Ra isotopes in the filter columns were in the range 10 000 Bq kg-1, while Th-228 activity concentration was roughly 3500 Bq kg-1.
Yadav KK, Gupta N, Kumar V, Khan SA, Kumar A. A review of emerging adsorbents and current demand for defluoridation of water: Bright future in water sustainability. Environment international. 2017 Nov 27;111:80-108. doi: 10.1016/j.envint.2017.11.014.
Fluoride contamination of groundwater is a serious problem in several countries of the world because of the intake of excessive fluoride caused by the drinking of the contaminated groundwater. Geological and anthropogenic factors are responsible for the contamination of groundwater with fluoride. Excess amounts of fluoride in potable water may cause irreversible demineralisation of bone and tooth tissues, a condition called fluorosis, and long-term damage to the brain, liver, thyroid, and kidney. There has long been a need for fluoride removal from potable water to make it safe for human use. From among several defluoridation technologies, adsorption is the technology most commonly used due to its cost-effectiveness, ease of operation, and simple physical process. In this paper, the adsorption capacities and fluoride removal efficiencies of different types of adsorbents are compiled from relevant published data available in the literature and represented graphically. The most promising adsorbents tested so far from each category of adsorbents are also highlighted. There is still a need to discover the actual feasibility of usage of adsorbents in the field on a commercial scale and to define the reusability of adsorbents to reduce cost and the waste produced from the adsorption process. The present paper reviews the currently available methods and emerging approaches for defluoridation of water.
Sillanpää M, Ncibi MC, Matilainen A, Vepsäläinen M. Removal of natural organic matter in drinking water treatment by coagulation: A comprehensive review. Chemosphere. 2017 Sep 25;190:54-71. doi: 10.1016/j.chemosphere.2017.09.113.
Natural organic matter (NOM) is a complex matrix of organic substances produced in (or channeled to) aquatic ecosystems via various biological, geological and hydrological cycles. Such variability is posing a serious challenge to most water treatment technologies, especially the ones designed to treat drinking water supplies. Lately, in addition to the fluctuating composition of NOM, a substantial increase of its concentration in fresh waters, and also municipal wastewater effluents, has been reported worldwide, which justifies the urgent need to develop highly efficient and versatile water treatment processes. Coagulation is among the most applied processes for water and wastewater treatment. The application of coagulation to remove NOM from drinking water supplies has received a great deal of attention from researchers around the world because it was efficient and helped avoiding the formation of disinfection by products (DBPs). Nonetheless, with the increased fluctuation of NOM in water (concentration and composition), the efficiency of conventional coagulation was substantially reduced, hence the need to develop enhanced coagulation processes by optimizing the operating conditions (mainly the amount coagulants and pH), developing more efficient inorganic or organic coagulants, as well as coupling coagulation with other water treatment technologies. In the present review, recent research studies dealing with the application of coagulation for NOM removal from drinking water supplies are presented and compared. In addition, integration schemes combining coagulation and other water treatment processes are presented, including membrane filtration, oxidation, adsorption and others processes.
Fu J, Lee WN, Coleman C, Nowack K, Carter J, Huang CH. Removal of disinfection byproduct (DBP) precursors in water by two-stage biofiltration treatment. Water research. 2017 Jun 27;123:224-235. doi: 10.1016/j.watres.2017.06.073.
The removal of precursors of 36 disinfection byproducts (DBPs) in effluents from flocculation/sedimentation process was evaluated across a pilot-scale two-stage biofiltration process, i.e., a sand/anthracite (SA) biofilter (empty bed contact time (EBCT) of 7.5 min) coupled with a biologically-active granular activated carbon (GAC) contactor (EBCT of 15 min). The biofiltration process exhibited a good capacity for removal of the total DBP formation potential (DBPFP) (by 25.90 ± 2.63%), and GAC contactors contributed most to the DBPFP removal (accounting for 60.63 ± 16.64% of the total removal). The removal percentage of DBPFPs of different structure types was in the following order: halonitroalkanes (58.50%) > haloaldehydes (33.62%) > haloacetic acids (HAAs, 28.13%) > haloalkanes (20.46%) > haloketones (13.46%) > nitrosamines (10.23%) > halonitriles (-8.82%) > haloalkenes (-9.84%). The precursors of bromo-DBPs (containing only bromine atoms) and maximal halogenated DBPs (containing 3 & 4 halo atoms) were removed largely compared to other DBPs. Among the total DBPFP, trihalomethanes (THMs), HAAs, and chloral hydrate were the dominant DBPs, and they accounted for >92% of the total targeted DBPs by weight. Pearson correlation analysis (CA) and principal components analysis (PCA) indicated a significant association among these dominant DBPs. Canonical correspondence analysis (CCA) revealed specific ultraviolet absorbance (SUVA254) could serve as a good surrogate parameter for DBPFP. Pre-chlorination upstream of the biofilters may not greatly impact the overall removal of DBPFP by SA/GAC biofiltration. In addition, results showed that SA/GAC biofiltration was a useful procedure to remove the inorganic DBP chlorite.