Organic Disinfection By-product Precursors Research Articles

Effects of ultrasonication on the DBP formation and toxicity during chlorination of saline wastewater effluents

Chlorine disinfection of saline wastewater effluents rich in bromide and iodide forms relatively toxic brominated and iodinated disinfection byproducts (DBPs). Ultrasonication is a relatively new water treatment technology, and it is less sensitive to suspended solids in wastewaters. In this study, we examined the effects of ultrasonication (in terms of reactor type and combination mode with chlorination) on the DBP formation and toxicity in chlorinated primary and secondary saline wastewater effluents. Compared with the chlorinated wastewater effluent samples without ultrasonication, ultrasonic horn pretreatment of the wastewater effluent samples reduced the total organic halogen (TOX) levels in chlorination by ∼30%, but ultrasonic bath pretreatment of the wastewater samples did not significantly change the TOX levels in chlorination, which might be attributed to the higher energy utilization and decomposition extent of organic DBP precursors in the ultrasonic horn reactor. Moreover, the TOX levels in the chlorinated samples with ultrasonic horn pretreatment (USH–chlorination), simultaneous treatment (chlorination+USH) and subsequent treatment (chlorination–USH) were also significantly reduced, with the maximum TOX reductions occurring in the samples with ultrasonic horn pretreatment. A toxicity index was calculated by weighting and summing the levels of total organic chlorine, total organic bromine and total organic iodine in each treated sample. The calculated toxicity index values of the chlorinated wastewater effluent samples followed a descending rank order of “chlorination” > “chlorination+USH” > “chlorination–USH” > “USH–chlorination”, with the lowest toxicity occurring in the samples with ultrasonic horn pretreatment. Then, a developmental toxicity bioassay was conducted for each treated sample. The measured toxicity index values of the chlorinated wastewater samples followed the same descending rank order.

High-Resolution Mass Spectrometry Identification of Novel Surfactant-Derived Sulfur-Containing Disinfection Byproducts from Gas Extraction Wastewater.

Introduction of oil and gas extraction wastewaters (OGWs) to surface water leads to elevated halide levels from geogenic bromide and iodide, as well as enhanced formation of brominated and iodinated disinfection byproducts (DBPs) when treated. OGWs contain high levels of chemical additives used to optimize extraction activities, such as surfactants, which have the potential to serve as organic DBP precursors in OGW-impacted water sources. We report the first identification of olefin sulfonate surfactant-derived DBPs from laboratory-disinfected gas extraction wastewater. Over 300 sulfur-containing DBPs, with 43 unique molecular formulas, were found by high-resolution mass spectrometry, following bench-scale chlor(am)ination. DBPs consisted of mostly brominated species, including bromohydrin sulfonates, dihalo-bromosulfonates, and bromosultone sulfonates, with chlorinated/iodinated analogues formed to a lesser extent. Disinfection of a commercial C12-olefin sulfonate surfactant mixture revealed dodecene sulfonate as a likely precursor for most detected DBPs; disulfur-containing DBPs, like bromosultone sulfonate and bromohydrin disulfonate, originated from olefin disulfonate species, present as side-products of olefin sulfonate production. Disinfection of wastewaters increased mammalian cytotoxicity several orders of magnitude, with chloraminated water being more toxic. This finding is important to OGW-impacted source waters because drinking water plants with high-bromide source waters may switch to chloramination to meet DBP regulations.

An evaluation of the adsorption process in removing organic substances in a pilot flow-type surface water treatment system

This article presents the results of the adsorption process effectiveness in treating surface water, especially in removing organic substances. The effectiveness of the adsorption system was evaluated at different levels of adsorption capacity exhaustion of the activated carbon bed, which was possible due to replacement of the beds during the study period. Studies have shown that among the removed substances, chlorinated disinfection byproduct precursors dominated, and during the period preceding bed replacement, the biological activity of microorganism populating the activated carbon ensured a reduction in not only organic but also non-organic food substrates. In such a adsorption bed populated with microorganism a nitrification process took place, indicating a high degree of process stability. Replacing the adsorption beds provided a significant increase in the effectiveness of removing organic substances, especially those absorbing UV light, therefore removing chlorinated organic disinfection by-product precursors.

Emerging investigators series: trihalomethane, dihaloacetonitrile, and total N-nitrosamine precursor adsorption by modified carbon nanotubes (CNTs) and CNT micropillars

Modified carbon nanotubes (CNTs) and CNT micropillars are shown to adsorb organic precursors of disinfection byproducts, most notably those of totalN-nitrosamines.

Evaluation of the effect of advanced coagulation process to optimize the removal of natural organic matter in water (Case study: drinking water of Mashhad’s Kardeh dam)

Natural Organic Matter (NOM) is a non-uniform mixture of organic compounds that enter water after synthesis of plants, animals, etc. Among the organic matters in natural waters, humic substances which usually exist as solutions have allocated a major portion to themselves and in addition to giving taste, color and odor to the water, they can intervene in the oxidization and removal of heavy metals such as arsenic, iron and manganese. Also, the natural organic precursors of disinfection by-products have been recognized as toxic or carcinogenic substances. The coagulation process is optimized as the most common system of water treatment in Iran for removing turbidity of water. This process is capable of removing the natural organic matter but the conditions for the removal of turbidity are constantly not identical with the optimum conditions for removing the NOM. Therefore, where NOM is the main pollutant, the traetment process should be optimized for removing NOM. Therefore, where NOM is the main pollutant, the traetment process should be optimized for removing NOM. After doing the common treatment, the water of Kardeh dam of Mashhad is used as drinking water of the city of Mashhad. By doing the water analysis experiments, the amounts of natural organic matter in the exiting water from water treatment plant was observed at 5 mg/l which is much higher than the world standards of drinking water. In this research the optimum conditions for the removal of NOM from drinking water of Kardeh dam have been examined. The experiments have been conducted at the laboratory scale and by Jar Test Device by different doses of two coagulants of alum and ferric chloride at various pH of water. It is concluded that these coagulation process by two coagulants remove NOM from drinking water and bring it to standards of US Environmental Protection Agency and World Health Organization. Keywords : advanced coagulation; natural organic matter; drinking water; city of Mashhad.

Discharges of produced waters from oil and gas extraction via wastewater treatment plants are sources of disinfection by-products to receiving streams

Fluids co-produced with oil and gas production (produced waters) are often brines that contain elevated concentrations of bromide. Bromide is an important precursor of several toxic disinfection by-products (DBPs) and the treatment of produced water may lead to more brominated DBPs. To determine if wastewater treatment plants that accept produced waters discharge greater amounts of brominated DBPs, water samples were collected in Pennsylvania from four sites along a large river including an upstream site, a site below a publicly owned wastewater treatment plant (POTW) outfall (does not accept produced water), a site below an oil and gas commercial wastewater treatment plant (CWT) outfall, and downstream of the POTW and CWT. Of 29 DBPs analyzed, the site at the POTW outfall had the highest number detected (six) ranging in concentration from 0.01 to 0.09μgL−1 with a similar mixture of DBPs that have been detected at POTW outfalls elsewhere in the United States. The DBP profile at the CWT outfall was much different, although only two DBPs, dibromochloronitromethane (DBCNM) and chloroform, were detected, DBCNM was found at relatively high concentrations (up to 8.5μgL−1). The water at the CWT outfall also had a mixture of inorganic and organic precursors including elevated concentrations of bromide (75mgL−1) and other organic DBP precursors (phenol at 15μgL−1). To corroborate these DBP results, samples were collected in Pennsylvania from additional POTW and CWT outfalls that accept produced waters. The additional CWT also had high concentrations of DBCNM (3.1μgL−1) while the POTWs that accept produced waters had elevated numbers (up to 15) and concentrations of DBPs, especially brominated and iodinated THMs (up to 12μgL−1 total THM concentration). Therefore, produced water brines that have been disinfected are potential sources of DBPs along with DBP precursors to streams wherever these wastewaters are discharged.

Simultaneous Compliance of TOC and Turbidity Related to Pathogen Breakthrough and THMs Control by Enhanced Coagulation

Since discovery of harmful disinfection by products (DBPs) like trihalomethanes (THMs)
 and haloacetic acids (HAAs) in chlorinated waters the removal of organic DBPs precursors
 gained priority in drinking water treatment. Historically, coagulation process was arranged
 to remove turbidity, typically related to pathogens occurrence, but nowadays it is usually
 optimized/enhanced for total organic carbon (TOC) reduction.
 This work dealt with the removal of TOC and turbidity by means of enhanced coagulation
 process using Al2(SO4)3⋅18 H2O and FeCl3⋅6H2O as coagulants for jar test without pH
 adjustment according to USEPA procedure. 15% of TOC removal required by USEPA
 D/DBPs rule (1998) was achieved using 30-50 mg l-1 of both coagulants. On the other
 hand, for compliance with more stringent MCL for total THMs in Italy (30 μg l-1) higher
 TOC removal (>30%) which needed of higher coagulants doses (80 mg l-1), was obviously
 required. Those high coagulant doses were also to be used for the compliance with the
 turbidity standard (<1NTU).

Effects of Physicochemical Properties of Nanofiltration Membranes on the Rejection of Small Organic DBP Precursors

AbstractIn this study, two types of commercial nanofiltration (NF) membranes (NF70 and NF270) were chosen to remove four model disinfection by-product (DBP) precursors (resorcinol, phloroglucinol, 3-hydroxybenzoic acid, and tannic acid) with different functional groups. The clean NF membranes were also characterized by physicochemical properties of membrane surface charge (determined by streaming potential measurement), hydrophobicity [determined by contact angle measurement), membrane surface morphology (determined by scanning electron microscopy and atomic force microscope (AFM)], surface roughness (determined by AFM), and surface composition (X-ray photoelectron spectroscopy) to validate the NF rejection mechanisms of the DBP precursors. The filtration experiments of the model DBP precursors were assessed under various pH values (3–10), and the removal efficiencies were good at high pH values for both membranes (84–99% at pH 9 and 89–100% at pH 10). Electrostatic repulsion is the prevailing mechanism f...

Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection by-product control: Application in a Western Australian water treatment plant

The removal of organic precursors of disinfection by-products (DBPs), i.e . natural organic matter (NOM), prior to disinfection and distribution is considered as the most effective approach to minimise the formation of DBPs. This study investigated the impact of the addition of powdered activated carbon (PAC) to an enhanced coagulation treatment process at an existing water treatment plant on the efficiency of NOM removal, the disinfection behaviour of the treated water, and the water quality in the distribution system. This is the first comprehensive assessment of the efficacy of plant-scale application of PAC combined with enhanced coagulation on an Australian source water. As a result of the PAC addition, the removal of NOM improved by 70%, which led to a significant reduction (80–95%) in the formation of DBPs. The water quality in the distribution system also improved, indicated by lower concentrations of DBPs in the distribution system and better maintenance of disinfectant residual at the extremities of the distribution system. The efficacy of the PAC treatment for NOM removal was shown to be a function of the characteristics of the NOM and the quality of the source water, as well as the PAC dose. PAC treatment did not have the capacity to remove bromide ion, resulting in the formation of more brominated DBPs. Since brominated DBPs have been found to be more toxic than their chlorinated analogues, their preferential formation upon PAC addition must be considered, especially in source waters containing high concentrations of bromide.

Modeling and design of ultraviolet reactors for disinfection by-product precursor removal

UV-photolysis and photo-initiated oxidation are promising technologies for water disinfection and the degradation of some organic precursors of disinfection by-products (DBPs). Due to the complexity of UV systems and the interaction of many parameters, the simulation of UV reactors for design optimization is crucial for the successful application of UV-based technologies. In this study, a UV-reactor model integrating photolysis-kinetics and reactor hydrodynamics was developed to simulate the degradation of organic material in various reactor geometries. The hydrodynamic model calculated by CFD was found to be in good agreement with particle image velocimetry (PIV) flow visualization data. The modelling results of two reactor geometries indicate that the decomposition of organic materials is strongly influenced by reactor hydrodynamics and the radiation fluence rate distribution. A more uniform flow rate and radiation distribution provided greater reactor performance under similar flow rates and lamp radiation powers. A parametric study of the reactors under various flow rates and lamp powers indicated that the impacts of reactor hydrodynamics and fluence rate on reactor performance become more pronounced at lower flow rates and higher lamp energy output.

Riverbank filtration: Effect of ground passage on NOM character

Research was conducted to explore the effect of underground travel on the character of the natural organic matter (NOM) originating from river water sources during riverbank filtration (RBF) at three Midwestern US drinking water utilities. Measurements of biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) showed significant reductions (50 to 90%) in the biodegradable portion of NOM at two of the sites. Specific UV-absorbance (SUVA) values suggested preferential reduction (26% reduction in SUVA) in UV-absorbing NOM at one of the sites but negligible changes in SUVA were observed at the other two sites. XAD-8 characterization was carried out on the river and well waters to investigate possible changes in the character of the NOM. The distribution of dissolved organic carbon (DOC) between the XAD-8 adsorbing (‘hydrophobic’) and non-adsorbing (‘hydrophilic’) fractions was similar between the river and well waters (40 to 70% hydrophilic and 30 to 60% hydrophobic), indicating no significant, consistent, preferential removal of either fraction upon ground passage. SUVA measurements on the separate XAD-8 fractions similarly showed no significant change during bank filtration. Disinfection by-product (DBP) formation testing was performed on the various fractions, keeping the ratio of chlorine:DOC:bromide constant. DBP formation testing showed no preferential formation between the hydrophobic and hydrophilic fractions in either the river or well waters. While the overall concentrations of organic DBP precursors are effectively reduced during bank filtration, the reductions appear to be largely the result of the reduction in NOM concentration rather than a consistent change in NOM character.