Tag Archives: water treatment

Biofiltration for removal of disinfection byproduct precursors

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.

Removal of Perfluoroalkyl Substances (PFASs) from Water

Kothawala DN, Köhler SJ, Östlund A, Wiberg K, Ahrens L. Influence of dissolved organic matter concentration and composition on the removal efficiency of perfluoroalkyl substances (PFASs) during drinking water treatment. Water research. 2017 May 24;121:320-328. doi: 10.1016/j.watres.2017.05.047.

Drinking water treatment plants (DWTPs) are constantly adapting to a host of emerging threats including the removal of micro-pollutants like perfluoroalkyl substances (PFASs), while concurrently considering how background levels of dissolved organic matter (DOM) influences their removal efficiency. Two adsorbents, namely anion exchange (AE) and granulated active carbon (GAC) have shown particular promise for PFAS removal, yet the influence of background levels of DOM remains poorly explored. Here we considered how the removal efficiency of 13 PFASs are influenced by two contrasting types of DOM at four concentrations, using both AE (Purolite A-600®) and GAC (Filtrasorb 400®). We placed emphasis on the pre-equilibrium conditions to gain better mechanistic insight into the dynamics between DOM, PFASs and adsorbents. We found AE to be very effective at removing both PFASs and DOM, while largely remaining resistant to even high levels of background DOM (8 mg carbon L-1) and surprisingly found that smaller PFASs were removed slightly more efficiently than longer chained counterparts, In contrast, PFAS removal efficiency with GAC was highly variable with PFAS chain length, often improving in the presence of DOM, but with variable response based on the type of DOM and PFAS chain length.

Biological Methods for Removing Nitrate from Drinking Water

Rezvani F, Sarrafzadeh MH, Ebrahimi S, Oh HM. Nitrate removal from drinking water with a focus on biological methods: a review. Environ Sci Pollut Res Int. 2017 May 31. doi: 10.1007/s11356-017-9185-0.

This article summarizes several developed and industrial technologies for nitrate removal from drinking water, including physicochemical and biological techniques, with a focus on autotrophic nitrate removal. Approaches are primarily classified into separation-based and elimination-based methods according to the fate of the nitrate in water treatment. Biological denitrification as a cost-effective and promising method of biological nitrate elimination is reviewed in terms of its removal process, applicability, efficiency, and associated disadvantages. The various pathways during biological nitrate removal, including assimilatory and dissimilatory nitrate reduction, are also explained. A comparative study was carried out to provide a better understanding of the advantages and disadvantages of autotrophic and heterotrophic denitrification. Sulfur-based and hydrogen-based denitrifications, which are the most common autotrophic processes of nitrate removal, are reviewed with the aim of presenting the salient features of hydrogenotrophic denitrification along with some drawbacks of the technology and research areas in which it could be used but currently is not. The application of algae-based water treatment is also introduced as a nature-inspired approach that may broaden future horizons of nitrate removal technology.

Removal of Quinolone Antibiotics from Water Using Activated Carbon

Fu H, Li X, Wang J, Lin P, Chen C, Zhang X, Suffet IHM. Activated carbon adsorption of quinolone antibiotics in water: Performance, mechanism, and modeling. Journal of environmental sciences (China). 2017 Jun;56:145-152. doi: 10.1016/j.jes.2016.09.010.

The extensive use of antibiotics has led to their presence in the aquatic environment, and introduces potential impacts on human and ecological health. The capability of powdered activated carbon (PAC) to remove six frequently used quinolone (QN) antibiotics during water treatment was evaluated to improve drinking water safety. The kinetics of QN adsorption by PAC was best described by a pseudo second-order equation, and the adsorption capacity was well described by the Freundlich isotherm equation. Isotherms measured at different pH showed that hydrophobic interaction, electrostatic interaction, and π-π dispersion force were the main mechanisms for adsorption of QNs by PAC. A pH-dependent isotherm model based on the Freundlich equation was developed to predict the adsorption capacity of QNs by PAC at different pH values. This model had excellent prediction capabilities under different laboratory scenarios. Small relative standard derivations (RSDs), i.e., 0.59%-0.92% for ciprofloxacin and 0.09%-3.89% for enrofloxacin, were observed for equilibrium concentrations above the 0.3 mg/L level. The RSDs increased to 11.9% for ciprofloxacin and 32.1% for enrofloxacin at μg/L equilibrium levels, which is still acceptable. This model could be applied to predict the adsorption of other chemicals having different ionized forms.

Oxidatively Modified Carbon (OMC) Removes Radioactive Elements

Artur Khannanov, Vadim V. Nekljudov, Airat Kiiamov, Ayrat M. Dimiev. Oxidatively modified carbon as efficient material for removing radionuclides from water. Carbon, Volume 115, May 2017, Pages 394–401http://dx.doi.org/10.1016/j.carbon.2017.01.025

There is a constant need to develop advantageous materials for removing radioactive waste from aqueous systems. Here we propose a new carbon-based material prepared by oxidative treatment of various natural carbon sources. The as-prepared oxidatively modified carbon (OMC) has an oxygen-rich surface, and retains its particulate granular texture. It has relatively low cost and can be used in traditional filtration columns. The sorption ability of OMC toward several metal cations is demonstrated. It is especially efficient toward Cs+ cations, the species that are among the most difficult to remove from the waters at the Fukushima nuclear plant. 

Polyvoxometalate Supported Ionic Liquid Phases (POM-SLIPS) Removes Contaminants from Water

Dr. Sven Herrmann, Dr. Laura De Matteis, Dr. Jesús M. de la Fuente, Dr. Scott G. Mitchell, Prof. Dr. Carsten Streb. Removal of Multiple Contaminants from Water by Polyoxometalate Supported Ionic Liquid Phases (POM-SILPs) Angewandte Chemie Volume 56, Issue 6 February 1, 2017 Pages 1667–1670

The simultaneous removal of organic, inorganic, and microbial contaminants from water by one material offers significant advantages when fast, facile, and robust water purification is required. Herein, we present a supported ionic liquid phase (SILP) composite where each component targets a specific type of water contaminant: a polyoxometalate-ionic liquid (POM-IL) is immobilized on porous silica, giving the heterogeneous SILP. The water-insoluble POM-IL is composed of antimicrobial alkylammonium cations and lacunary polyoxometalate anions with heavy-metal binding sites. The lipophilicity of the POM-IL enables adsorption of organic contaminants. The silica support can bind radionuclides. Using the POM-SILP in filtration columns enables one-step multi-contaminant water purification. The results show how multi-functional POM-SILPs can be designed for advanced purification applications.

Ozone regeneration of GAC to control THMs

He X, Elkouz M, Inyang M, Dickenson E, Wert EC. Ozone regeneration of granular activated carbon for trihalomethane control. Journal of hazardous materials 2016 Dec 9;326:101-109. doi: 10.1016/j.jhazmat.2016.12.016.

Spatial and temporal variations of trihalomethanes (THMs) in distribution systems have challenged water treatment facilities to comply with disinfection byproduct rules. In this study, granular activated carbon (GAC) and modified GAC (i.e., Ag-GAC and TiO2-GAC) were used to treat chlorinated tap water containing CHCl3 (15-21μg/L), CHBrCl2 (13-16μg/L), CHBr2Cl (13-14μg/L), and CHBr3 (3μg/L). Following breakthrough of dissolved organic carbon (DOC), GAC were regenerated using conventional and novel methods. GAC regeneration efficiency was assessed by measuring adsorptive (DOC, UV absorbance at 254nm, and THMs) and physical (surface area and pore volume) properties. Thermal regeneration resulted in a brief period of additional DOC adsorption (bed volume, BV, ∼6000), while ozone regeneration was ineffective regardless of the GAC type. THM adsorption was restored by either method (e.g., BV for ≥80% breakthrough, CHBr3 ∼44,000>CHBr2Cl ∼35,000>CHBrCl2 ∼31,000>CHCl3 ∼7000). Cellular and attached adenosine triphosphate measurements illustrated the antimicrobial effects of Ag-GAC, which may have allowed for the extended THM adsorption compared to the other GAC types. The results illustrate that ozone regeneration may be a viable in-situ alternative for the adsorption of THMs during localized treatment in drinking water distribution systems.