Henry V. Mott

Association of hydrophobic organic contaminants with soluble organic matter: evaluation of the database of Kdoc values

Abstract Natural dissolved organic matter is ubiquitous in the environment and comprises a soluble compartment of any environmental system containing water. The association of contaminants with this compartment and the facilitation or hindrance of migration effected by this association can be important in the overall fate-migration process, thus quantitative evaluations of the coefficients describing association of hydrophobic organic contaminants (HOCs) with natural dissolved organic matter, from various sources, have been completed using several distinct methodologies: gas–aqueous partitioning; reverse-phase separation; dialysis; liquid–solid partitioning; fluorescence quenching and apparent solubility enhancement. Each of these methodologies and an evaluation of the quality of its results are described herein. Apparent solubility enhancement methods appear to be the most universally applicable, being subject to the least number of potential experimental artifacts. The accuracy of values obtained using the gas–aqueous partitioning and reverse-phase separation methods is suspect. Fluorescence quenching methods are limited to HOCs that fluoresce and are subject to interferences that potentially lead to positive bias. Dialysis methods are subject to anomalies that lead to a potentially negative bias of the results. Liquid–solid partitioning methods are subject to a number of potential random errors and biases. The hydrophobicity and molecular structure of the HOC, the composition and character of the natural organic matter and the background solution conditions all potentially affect the magnitude of the association coefficient. These factors are summarized and discussed. A database of coefficients and methodologies for obtaining accurate estimates of the distribution coefficient describing the association of HOCs with natural organic solids currently exists. This paper presents a first attempt at assembling a similar database and set of methodologies for accurate estimation of the coefficients quantitatively describing the association of HOCs with natural dissolved organic matter. This assembled data base is found to be lacking in terms of its predictive utility.

Effects of chlortetracycline amended feed on anaerobic sequencing batch reactor performance of swine manure digestion.

The effects of antimicrobial chlortetracycline (CTC) on the anaerobic digestion (AD) of swine manure slurry using anaerobic sequencing batch reactors (ASBRs) was investigated. Reactors were loaded with manure collected from pigs receiving CTC and no-antimicrobial amended diets at 2.5 g/L/d. The slurry was intermittently fed to four 9.5L lab-scale anaerobic sequencing batch reactors, two with no-antimicrobial manure, and two with CTC-amended manure, and four 28 day ASBR cycles were completed. The CTC concentration within the manure was 2 8 mg/L immediately after collection and 1.02 mg/L after dilution and 250 days of storage. CTC did not inhibit ASBR biogas production extent, however the volumetric composition of methane was significantly less (approximately 13% and 15% for cycles 1 and 2, respectively) than the no-antimicrobial through 56 d. CTC decreased soluble chemical oxygen demand and acetic acid utilization through 56 d, after which acclimation to CTC was apparent for the duration of the experiment.

Assessing solid waste recycling opportunities for closed campuses

Purpose – The commercial and residential refuse generated by Ellsworth Air Force Base, USA was characterized and analyzed for collection procedures, and the opportunities for increasing the amount of solid waste that could be recycled were evaluated.Design/methodology/approach – Random loads of hauled solid waste (an average 3.0 US tons/load) from different waste streams of Ellsworth Air Force Base were sorted. The weight fraction of each category of recyclable material derived from the hand sorting operations was applied to the three years of mixed waste tonnage in order to estimate the tonnage of each recyclable category disposed of as refuse during each year. The assessment of the data obtained from three full calendar years focused on the mixed solid waste generated from commercial and residential areas such as offices, childcare, lodging, supermarkets, food service facilities, and others.Findings – Over 2,500 tones of recycling opportunities were missed during the 1999‐2001 calendar years. The charac...

Impact of chlortetracycline on sequencing batch reactor performance for swine manure treatment

Treatment of aged (500 day, 4°C stored) chlortetracycline (CTC; 0, 20, 40, 80 mg/L CTC)-amended swine manure using two cycle, 22 day stage anaerobic sequencing batch reactors (SBR) was assessed. Eighty milligrams per liter CTC treatment inhibited SBR treatment efficiencies, although total gas production was enhanced compared to the no-CTC treatment. The 20 and 40 mg/L CTC treatments resulted in either slight or no differences to SBR treatment efficiencies and microbial diversities compared to the no-CTC treatment, and were generally similar to no-CTC treatments upon completion of the first 22 day SBR cycle. All CTC treatments enhanced SBR gas generation, however CH(4) yields were lowest for the 80 mg/L CTC treatment (0.111L CH(4)/g tCOD) upon completion of the second SBR react cycle. After a 22 day acclimation period, the 80 mg/L CTC treatment inhibited methanogenesis due to acetate accumulation, and decreased microbial diversity and CH(4) yield compared to the no-CTC treatment.