Electrochemical disinfection of Escherichia coli in the presence and absence of primary sludge particulates.

Electrochemical (EC) residual disinfection of Escherichia coli (E. coli) in the presence and absence of primary sludge particulates (PSPs) was studied. The kinetics followed a first-order rate law. When PSPs were absent, the EC residual disinfection rate coefficient (k) increased linearly with EC pretreatment energy (EC, 0-0.63 kWh/m(3)). However, with 143 mg PSPs/L, k first increased linearly with EC (0-0.28 kWh/m(3)) and then decreased linearly with EC (0.28-0.42 kWh/m(3)). H2O2 was detected during EC pretreatment in PSPs-free samples and the H2O2 concentration (CH) increased with EC (0-0.83 kWh/m(3)) linearly. Chloride was detected in PSPs aqueous samples (143 mg PSPs/L) and its concentration (CC) changed during EC pretreatment: initially, a decrease of CC was observed when EC increased from 0 to 0.28 kWh/m(3), followed by an increase of CC when EC increased 0.28-0.42 kWh/m(3). In both cases, k correlated to the initial post-EC chloride concentration (CCI) in an inverse linear relationship. This two-stage change of CC and k was caused by a combination of two reactions: anodic oxidation of chloride and the reaction of chloramines with excess chlorine. This paper explains the mechanisms underlying EC residual disinfection in the presence and absence of PSPs, and proposes a feasible strategy for EC disinfection when PSPs are present, an approach that could be useful in the treatment of combined sewage overflow (CSO).

Hydrolysis of the soluble fluorescent molecule carboxyumbelliferyl-beta-D-glucuronide by E. coli beta-glucuronidase as applied in a rugged, in situ optical sensor.

Techniques utilizing ß-glucuronidase (GUS) activity as an indicator of Escherichia coli (E. coli) presence use labeled glucuronides to produce optical signals. Carboxyumbelliferyl-ß-d-glucuronide (CUGlcU) is a fluorescent labeled glucuronide that is soluble and highly fluorescent at natural water pHs and temperatures and, therefore, may be an ideal reagent for use in an in situ optical sensor. This paper reports for the first time the Michaelis-Menten kinetic parameters for the binding of E. coli GUS with CUGlcU as K(m)=910 µM, V(max)=41.0 µM min(-1), V(max)/K(m) 45.0 µmol L(-1)min(-1), the optimal pH as 6.5 ± 1.0, optimal temperature as 38°C, and the Gibb's free energy of activation as 61.40 kJ mol(-1). Additionally, it was found CUGlcU hydrolysis is not significantly affected by heavy solvents suggesting proton transfer and solvent addition that occur during hydrolysis are not limiting steps. Comparison studies were made with the more common fluorescent molecule methylumbelliferyl-ß-d-glucuronide (MUGlcU). Experiments showed GUS preferentially binds to MUGlcU in comparison to CUGlcU. CUGlcU was also demonstrated in a prototype optical sensor for the detection of E. coli. Initial bench testing of the sensor produced detection of low concentrations of E. coli (1.00 × 10(3)CFU/100mL) in 230 ± 15.1 min and high concentrations (1.05×10(5)CFU/100mL) in 8.00 ± 1.01 min.

Effects of primary sludge particulate (PSP) entrapment on ultrasonic (20 kHz) disinfection of Escherichia coli.

The role of primary sludge particulates (PSPs) in ultrasonic disinfection of Escherichia coli (E. coli) was investigated. Entrapment of E. coli by PSP was directly observed through scanning electron microscope (SEM) after E. coli and PSP were incubated together in water for 24 h at 35 °C. Entrapment coefficient was proposed for the first time to reflect the ability of PSP to entrap E. coli and was estimated as 1.4 × 10(3) CFU/mg PSP under our experimental conditions. Ultrasonication (20 kHz) of different E. coli-PSPs solutions showed that the entrapped E. coli cells were protected by PSP from ultrasonication and the unentrapped cells were not. However, the protection of entrapped E. coli cells gradually decreased as ultrasonication proceeded, suggesting the ability of power ultrasonication to deprotect the entrapped E. coli cells. SEM studies suggested a two-step mechanism for ultrasonic (20 kHz) disinfection of entrapped E. coli: breakdown of the protective PSP refugia and disinfection of the exposed E. coli cells. This research will enable more informed decisions about disinfection of aqueous samples where porous PSP are present.

Copper doping improves hydroxyapatite sorption for arsenate in simulated groundwaters.

Hydroxyapatite (HAP) has been widely used to immobilize many cationic heavy metals in water and soils. Compared with its strong sorption for metal cations, the abilities of HAP to sorb metal anions, such as arsenic, are less significant. Improving HAP sorption for anionic arsenic species is important for expanding its application potential because the presence of arsenic in the environment has raised serious health concerns and there is need for cost-effective remediation methods. In this work, we report an innovative method of copper doping to improve a synthetic HAP sorption for arsenate, which is a primary aqueous arsenic species, in simulated groundwaters. The undoped HAP and copper doped HAP (CuHAP) were characterized with XRD, FTIR, N(2) adsorption, and SEM, and then evaluated as sorbents for arsenate removal tests. The experimental results suggest that copper doping changed the morphology and increased the surface area of HAP. The CuHAP sorbed 1.6-9.1x more arsenate than the undoped HAP did in a simulated groundwater at pH of 7.7-8.0. The improved arsenate sorption is presumably due to the increase in surface area of HAP as a result of copper doping. In addition to the copper doping level, the arsenate sorption to HAP and CuHAP can also be increased with increasing water pH and calcium concentration. The experimental data indicate that sorbent dissolution is an important factor governing arsenate sorption to HAP and CuHAP.

Fast selective detection of polar brominated disinfection byproducts in drinking water using precursor ion scans.

Brominated disinfection byproducts (DBPs), formed from the reaction of disinfectant(s) with natural organic matter and bromide in raw water, are generally more cytotoxic and genotoxic than their chlorinated analogues. Brominated DBPs have been intensively studied over the past 35 years, yet only a fraction of the total organic bromine formed during disinfection has been identified. A significant portion of the unaccounted total organic bromine may be attributed to polar/highly polar brominated DBPs. In this work, a method for fast selective detection of polar/ highly polar brominated DBPs in drinking water was developed using negative ion electrospray ionization-triple quadrupole mass spectrometry (ESI-tqMS) by setting precursor ion scans of m/z 79 and 81. This method was conducted without liquid chromatography separation. The results demonstrate that the ESI-tqMS precursor ion scan is an effective tool for the selective detection of electrospray ionizable bromine-containing compounds in a complex mixture. Many polar/ highly polar bromine-containing DBPs were tentatively found in two drinking water samples, and some of them may be new brominated DBPs that have not been previously reported. This method was also extended for the selective detection of polar bromine-containing compounds/contaminants in groundwater, surface water and wastewater.

Effect of NOM on arsenic adsorption by TiO(2) in simulated As(III)-contaminated raw waters.

The effect of natural organic matter (NOM) on arsenic adsorption by a commercial available TiO(2) (Degussa P25) in various simulated As(III)-contaminated raw waters was examined. Five types of NOM that represent different environmental origins were tested. Batch adsorption experiments were conducted under anaerobic conditions and in the absence of light. Either with or without the presence of NOM, the arsenic adsorption reached steady-state within 1h. The presence of 8 mg/L NOM as C in the simulated raw water, however, significantly reduced the amount of arsenic adsorbed at the steady-state. Without NOM, the arsenic adsorption increased with increasing solution pH within the pH range of 4.0-9.4. With four of the NOMs tested, the arsenic adsorption firstly increased with increasing pH and then decreased after the adsorption reached the maximum at pH 7.4-8.7. An appreciable amount of arsenate (As(V)) was detected in the filtrate after the TiO(2) adsorption in the simulated raw waters that contained NOM. The absolute amount of As(V) in the filtrate after TiO(2) adsorption was pH dependent: more As(V) was presented at pH>7 than that at pH<7. The arsenic adsorption in the simulated raw waters with and without NOM were modelled by both Langmuir and Frendlich adsorption equations, with Frendlich adsorption equation giving a better fit for the water without NOM and Langmuir adsorption equation giving a better fit for the waters with NOM. The modelling implies that NOM can occupy some available binding sites for arsenic adsorption on TiO(2) surface. This study suggests that in an As(III)-contaminated raw water, NOM can hinder the uptake of arsenic by TiO(2), but can facilitate the As(III) oxidation to As(V) at TiO(2) surface under alkaline conditions and in the absence of O(2) and light. TiO(2) thus can be used in situ to convert As(III) to the less toxic As(V) in NOM-rich groundwaters.

Effect of copper(II) on natural organic matter removal during drinking water coagulation using aluminum-based coagulants.

Coagulation has been proposed as a best available technology for controlling natural organic matter (NOM) during drinking water treatment. The presence of heavy metals such as copper(II) in source water, which may form copper-NOM complexes and/or interact with a coagulant, may pose a potential challenge on the coagulation of NOM. In this work, the effect of copper(II) on NOM removal by coagulation using alum or PAX-18 (a commercial polymerized aluminum chloride from Kemiron Inc., Bartow, Florida) was examined. The results show that the presence of 1 to 10 mg/L of copper(H) in the simulated waters improved the total organic carbon (TOC) removal by up to 25% for alum coagulation and by up to 22% for PAX-18 coagulation. The increased NOM removal with the presence of copper(II) in the waters can most likely be ascribed to the formation copper-NOM complexes that may be more adsorbable on aluminum precipitates and to the formation of copper(II) co-precipitates that may also adsorb NOM. The presence of 1 to 5 mg/L of copper(I) in the waters containing 3 mg/L NOM as carbon was reduced below the maximum contaminant level goal (1.3 mg/L as copper) using either coagulant. The results suggest that the presence of copper(H) in source water may not adversely affect the NOM removal by coagulation. A good linear correlation was observed between the TOC removal efficiency and the log-total moles of the precipitated metals, which include the metal ion from a coagulant and the divalent metal ion(s) in source water.

Abiotic transformation of DDT in aqueous solutions.

Significant concentrations of chlorinated pesticides such as 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its two main transformation products, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) are still present in soil and sediment systems more than 30 years after DDT use was banned in the United States. DDT enters waterways via the runoff from industrial point sources, agricultural lands and atmospheric deposition. We evaluated zero-valent iron (Fe(0)), ferrous sulfide (FeS), as well as combining them with hydrogen peroxide (H(2)O(2)) as viable treatment technologies for degrading DDT in an aqueous solution. Treatment of DDT with Fe(0) and FeS resulted in approximately 88% and 56% transformation of DDT within 150h, respectively. DDE production was insignificant in all systems. The DDT removal was slower with FeS than with Fe(0), but the amounts of DDD and DDE produced did not exceed baseline. Treatment with a 1:1 mixture of Fe(0)-FeS removed about 95% of the added mass of DDT within 4days and generated significant amounts of DDD and minor amounts of DDMU. When small amounts of H(2)O(2) were introduced halfway through the Fe(0) and FeS treatment times, the mass of DDT decreased by 87% and 96%, respectively, within 2days. Our results demonstrate that mixtures of Fe(0)-FeS in combination with H(2)O(2) can be used for rapid and efficient removal of DDT from aqueous solutions.

Development of thermal programmed desorption mass spectrometry methods for environmental applications.

The physical availability of hydrophobic organic contaminants (HOCs) bound to soils and sediments often controls their environmental toxicity. Currently, complicated and time extensive procedures are necessary to determine physical availability. The development of thermal programmed desorption mass spectrometry (TPD-MS) techniques for environmental samples may make it possible to evaluate the physical availability of HOCs in soils and sediments and also calculate relevant release energy values for bound contaminants. This work focused on developing the analytical protocols and data processing requirements for studying the desorption of HOCs from various simple geosorbents using TPD-MS. The work seeks to document the use of the TPD-MS method as an environmental assessment tool and provide the reader with a working knowledge of the entire process.

Effects of temperature and chemical addition on the formation of bromoorganic DBPs during ozonation.

The effects of temperature and addition of OH radical scavengers/enhancers or HOBr scavenger on the formation of bromoorganic disinfection byproducts (DBPs) from ozonation of six raw waters were studied in true batch reactors. The formation of bromoorganic DBPs during ozonation generally increased with the increase of temperature, but might also decrease for the waters with somewhat higher values of specific UV absorbance (SUVA). The addition of hydrogen peroxide, ethanol, or ammonium dramatically decreased the formation of bromoorganic DBPs; t-butanol addition significantly increased the formation of bromoorganic DBPs; bicarbonate addition might increase or decrease bromoorganic DBP formation depending on the water source. For all the waters treated with the chemical addition, the level of total organic bromine (TOBr) varied with the same pace as that of ozone exposure (CT), which suggests that TOBr formed during ozonation may be used to estimate the CT, a measure for the achieved degree of disinfection. The results demonstrate that for each water, the correlation between TOBr and CT was less affected by the change of chemical composition of the water than that between BrO(3)(-) and CT; for a given chemical composition and temperature of a water, there generally were well-defined relationships between TOBr and CT, and bromoform and CT just as that between BrO(3)(-) and CT. The possible mechanisms behind the linear functions of TOBr or BrO(3)(-) versus CT were given. Further study is needed to examine whether the trends found in this research can be applicable for the high SUVA waters.

Model verification of thermal programmed desorption-mass spectrometry for estimation of release energy values for polycyclic aromatic hydrocarbons on mineral sorbents.

The physical availability of organic compounds in soil and sediment strongly influences their bioavailability and toxicity. Previous work has indicated that physical availability changes throughout the processes of aging and treatment and that it can be linked to the energy required to release the compound from its sorbent matrix, with a higher energy indicating a more tightly bound compound. This study focused on determining release energy values for various mineral geosorbents (glass beads, sand, and kaolin) contaminated with a 16 polycyclic aromatic hydrocarbon (PAH) mixture. The sorbents were analyzed using thermal program desorption/mass spectrometry (TPD/MS) and the release energy values were calculated from the resulting thermograms utilizing a nonlinear fit of the analytical solution to a simplified version of the Polanyi-Wigner equation. This solution method resulted in a series of combinations of values for the pre-exponential factor (v) and release energy (E) that produced desorption rate curves with similar errors when fit to actual data sets. These combinations can be viewed as an error surface, which clearly shows a valley of minimum error values spanning the range of both E and v. This indicates that this method may not provide a unique set of E- and v-values and suggests that the simplified version of the Polanyi-Wigner equation cannot be used to determine release energy based on TPD data alone.

Particle-scale understanding of the bioavailability of PAHs in sediment.

This study reports results of sediment bioslurry treatment and earthworm bioaccumulation for polycyclic aromatic hydrocarbon (PAH) contaminants found in sediment dredged from Milwaukee Harbor. A significant finding was that bioslurry treatment reduced PAHs on the sediment clay/silt fraction but not on the sediment coal-derived fraction and that PAH reduction in the clay/silt fraction correlated with substantial reduction in earthworm PAH bioaccumulation. These findings are used to infer PAH bioavailability from characterization of particle-scale PAH distribution, association, and binding among the principal particle fractions in the sediment. The results are consistent with work showing that the sediment comprised two principal particle classes for PAHs, coal-derived and clay/silt, each having much different PAH levels, release rates, and desorption activation energies. PAH sorption on coal-derived particles is associated with minimal biodegradation, slow release rates, and high desorption activation energies, while PAH sorption on clay/silt particles is associated with significant potential biodegradability, relatively fast release rates, and lower desorption activation energies. These characteristics are attributed to fundamental differences in the organic matter to which the PAHs are sorbed. Although the majority of the PAHs are found preferentially on coal-derived particles, the PAHs on the clay/silt sediment fraction are more mobile and available, and thus potentially of greater concern. This study demonstrates that a suite of tests comprising both bioassays and particle-scale investigations provide a basis to assess larger-scale phenomena of biotreatment of PAH-impacted sediments and bioavailability and potential toxicity of PAH contaminants in sediments. Improved understanding of contaminant bioavailability aids decision-making on the effectiveness of biotreatment of PAH-impacted sediments and the likelihood for possible reuse of dredged sediments as reclaimed soil or fill.