James N. Jensen

Dechlorination of chlorendic acid with ozone

Abstract An experimental study was conducted to investigate the use of ozone to dechlorinate chlorendic acid [1,4,5,6,7,7-hexachlorobicyclo-(2,2,1)-hept-5-ene-2,3-dicarboxylic acid; CAS Number 115-28-6]. The dechlorination and subsequent degradation of chlorendic acid by ozonation is influenced by the pH, applied ozone dose and bicarbonate concentration. A change in the initial chlorendic acid concentration to 50, 100 and 200 mg/l did not influence the rate of degradation of chlorendic acid. Ultraviolet radiation alone also dechlorinated chlorendic acid. Ultraviolet radiation (u.v.) was also shown to greatly enhance the oxidation of chlorendic acid in the presence of ozone. In a typical case, 80% dechlorination of chlorendic acid was obtained in 60 min when using an ozone dose of 125 mg/min ozone at pH 7.4. In addition to the experimental results, a model describing the dechlorination of chlorendic acid is presented. The pseudo-first order rate constants for a two-step model were calculated and ranged from 0.002 to 0.295 min−1 for the first step and 0.008 to 6 × 1012 min−1 (calculated) for the second step. The magnitude of the rate constants and corresponding rates of dechlorination of chlorendic acid were shown to be dependent upon the production and/or scavenging of hydroxyl radicals in solution. Conditions favoring radicals in solution, such as high pH and the addition of u.v., resulted in much faster dechlorination. The conditions which did not favor radicals, such as low pH and the addition of bicarbonate, resulted in slower dechlorination.

Combined use of heat and oxidants for controlling adult zebra mussels

Abstract The results of an experimental study are presented that demonstrate the use of chlorine or ozone to control zebra mussels at temperatures from 30 to 36°C. Control studies were conducted with no oxidant present. Three acclimation temperature ranges were tested: 0–5, 10–15, and 20–25°C. Chlorine was tested at 0.1 and 0.5 mg/L; ozone at 0.5 mg/L. Mortality was described by a cumulative normal distribution, from which times to 95% mortality were estimated and used as a dependent variable for hypothesis testing. Study results showed that the addition of chlorine or ozone was more effective than heat alone at test temperatures above 30°C. Compared to heat alone, the combined use of heat and oxidants decreased the time to 95% mortality by more than 95% at 30°C. Above 30°C, the benefits of the combined treatment strategy decreased with increasing test temperature. At 36°C, the benefits of the combined treatment strategy over heat alone were minimal. Acclimation temperature was important only for heat alone and for mussels acclimated at 0–5°C. The addition of chlorine or ozone at elevated temperatures can reduce mortality times by as much as three orders of magnitude compared to oxidant addition at ambient temperatures. The results of the study should be of significance to power plants or industries where excess heat is available to raise water temperatures.

Congener Level PCB Desorption Kinetics of Field-Contaminated Sediments

The purpose of this research was to study congener level PCB desorption kinetics of field-contaminated sediments and develop a simple methodology to analyze the desorption behavior. Batch desorption kinetic studies were conducted using XAD-4 resin. Two-phase desorption kinetics were observed for most PCB congeners, consisting of an initial fast rate followed by an extended period of slow rate. A dual first-order rate model was fitted to the PCB desorption data to estimate PCB concentrations in the fast and slow desorbing pools. The fast and slow desorption rates were found to decrease with increasing chlorina-tion of PCB congeners, decreasing ortho chlorination, and decreasing temperature. Estimated first-order desorption rate constants for the fast pools were found to be two orders of magnitude higher than those for the corresponding slow pools. The log of first-order rate constants for the different PCB congeners were found to be linearly related to the log of octanol-water partition coefficients. There...

Continuous culture biodegradation of simazine's chemical oxidation products

Abstract Experimental studies were conducted to assess the continuous culture biodegradation of s -triazines which originate from the chemical oxidation of simazine. Simazine is a herbicide found widely in surface and groundwaters. The four s -triazines selected for study, didealkyl atrazine (CAAT), ammeline (OAAT), ammelide (OOAT), and cyanuric acid (OOOT), originate from the ozone/UV oxidation of simazine. Decreases in continuous culture net growth rate, decreases in C: s -triazine-N feed ratio, and increases in inorganic nitrogen either through addition to the feed or by nitrogen fixation resulted in poorer s -triazine removal. For each process variable studied, the reduction in removal efficiency was s -triazine specific. In general, the greatest reductions in removal efficiency was observed for CAAT followed by OAAT, OOAT, and OOOT indicating that the s -triazine ring substituent group is an important factor in determining its effectiveness as a nitrogen source for microbial metabolism. The relationship between ring substituent and s -triazine metabolism demonstrates the beneficial role that chemical oxidation can play in subsequent s -triazine biodegradation. The application of chemical oxidation may enable the use of existing biological process infrastructure, primarily municipal POTWs where nitrogen limitations do not typically exist, for the treatment of s -triazines.

Dissolved PCB congener distribution in generator column solutions

Abstract A generator column technique previously used to study the solubility of sparingly soluble compounds, has been employed in this study to prepare high throughput aqueous PCB solutions for use in treatability studies. In the present study, Aroclor 1242 mixture was used to load the generator column. The total PCB concentration and the PCB congener distribution pattern in the effluent changed with time, with lower chlorinated congeners eluting faster than the higher chlorinated ones. Collection of over 300 bed volumes of effluent from two such generator columns provided PCB solutions which showed 75–90% similarity to the original Aroclor 1242 congener distribution. In this paper, the observed distribution of PCB congeners in the generator column effluent with time is presented and discussed. A reasonable prediction of effluent PCB concentration from the generator column was possible using Raoults Law for ideal solutions.

Response of zebra mussel veligers to chemical oxidants

Abstract Experimental studies using chlorine, hydrogen peroxide and ozone showed two responses by zebra mussel veligers. First, veligers readily perceived the presence of oxidants (> 0.1 mg/l for chlorine and ozone) and responded by retracting the velum and ceasing swimming and feeding activities. Under these conditions, veligers are prevented from attaching to solid surfaces. Second, continuous exposure to these oxidants caused death. Complete mortality by chlorine or ozone (0.5–1 mg/l) at 18–22°C required continuous exposure of about 18 and 5 h, respectively. Either chlorine or ozone should be effective in controlling zebra mussel veligers. Hydrogen peroxide was observed to be effective in preventing attachment but only at high doses relative to chlorine and ozone.

Disinfection model based on excess inactivation sites: implications for linear disinfection curves and the Chick-Watson dilution coefficient.

Current disinfection models generally are either empirical modifications of Chicks law (linear survivor curves) or hit or site models modified from the radiation literature. In this paper, a general disinfection model is developed that assumes a large number of inactivation sites. From a probabilistic model of damaged site distribution, the normalized number of surviving organisms is described as the cumulative distribution function (cdf) of the normal distribution, with the independent variable equal to a measure of damage and the mean and variance equal and determined by dose-response submodels. Submodels were developed for chemical disinfectants without disinfectant demand, ultraviolet radiation, and chemical disinfectants with first-order disinfectant demand. This infinite site model reproduces linear, shouldering, and tailing survivor curves from literature data. In addition, it predicts Chick-Watson dilution coefficients in the range observed in the literature. The infinite site model offers the interpretation that linear, shoulder, tailing, and biphasic survivor curves and the apparent Chick-Watson dilution coefficient are ramifications of the normal cdf, rather than mechanistic laws.

Sequential chemical/biological oxidation of chlorendic acid

Chlorendic acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of chlorendic acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of chlorendic acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, chlorendic acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, chlorendic acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of chlorendic acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, chlorendic acid was not degradable. Biodegradation efficiency (DOC removal) of chlorendic acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from chlorendic acid achieved 89% biodegradation. Biodegradation rates of chlorendic acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of chlorendic acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.