Recent investigations have shown that engineered nanomaterials such as carbon nanotubes (CNTs) are a source and precursor for disinfection byproduct (DBP) formation. The aim of this study was to extend previous research of CNTs by investigating the potential for other classes of CNTs to generate disinfection byproducts (DBP) during chlorination. We examined particular types of CNTs with surface groups analogous to suspected model precursors for DBP formation.Specifically, we conducted experiments to determine the formation of haloacetic acids (HAAs) and N-nitrosodimethylamine (NDMA) via the chlorination of carbon nanotubes. Polymer coated CNTs generated the greatest total HAA concentration of up to 170 μg-HAA/mg-CNT. Results showed that the presence of surface oxide groups (e.g. surface carboxylic acid groups) promotes HAA formation. We observed a reasonably strong correlation between the extent of HAA formation and the concentration of surface oxygen on the CNT surface. Results also showed that CNTs behave similar to model precursors for di- and trichloroacetic acid formation (DCAA and TCAA, respectively). Nitrogen containing CNTs have been shown as source of N-nitrosodimethylamine (NDMA). Surprisingly, CS PEG, which does not contain N, produces NDMA when reacted with ethylenediamine (EDA). Ultimately, EDA is contributing N to CS PEG by sorbing to the CNT surface, which is the likely source of N for NDMA formation. At lower EDA concentrations, NDMA production is limited by available EDA. Conversely, at higher EDA concentrations, NDMA production is limited by available chlorine that is in competition with EDA and the CNT surface.

acase@tulane.edu / Worldwide, more than two billion people rely on onsite sanitation technologies for excreta treatment and/or disposal. The proper management of domestic septage remains a challenge in most cities in developing countries. A field experiment was conducted in Kinshasa/DR Congo from June 2013 to September 2015 to explore the effectiveness of lagoon treatment for the disinfection and the stabilization of domestic septage. Four lagoons were designed by combining two design factors: Total Solids content (< 5% versus 8% - 12%) and the protection from rainfall (Yes versus No). Each lagoon was a truncated pyramid with a usable volume of 28 m3 and 3m depth. The monitoring of pathogens inactivation was conducted from September 2014 over 12,4 months using coliforms bacteria and Ascaris lumbricoides eggs in sentinel chambers as indicator organisms, respectively with the multiple tubes technique and the Tulane Method. Local climate conditions and abiotic characteristics of the stored septage were monitored monthly. Four-log reduction of fecal coliforms organisms were observed within 10 months of septage storage in the two types of lagoons. At the end of this study, 3-log and less than 2-log reductions of Ascaris eggs were observed, respectively in the lagoons with high and low solids content. The inactivation curve of Ascaris eggs was characterized by a lag phase with a slight inactivation followed by an active inactivation phase. The inactivation rate constants for the active phase were 0.071 and 0.034 day-1, respectively in the lagoons with high and low solids content. Multiple linear regression model showed that the storage time, pH, and TS were significantly associated with percent Ascaris eggs inactivation. Trace elements concentrations in the final product were below threshold ceiling values for their reuse in agriculture. Total volatile solids concentration reduction in the lagoons with high solids content was below the stabilization limit set at 38% by USEPA. In conclusion, lagoon storage of domestic septage with at least 8% TS for 12 to 15 months is an effective option for the disinfection of domestic septage under the conditions of this study. The resulting biosolids constitute a value-added product which can be safely reused in agriculture. / 1 / Konde, Nkiama N.

In this thesis, detection of active water-borne bacteria was achieved by combining flow cytometry with vital dyes that characterise the metabolic status of cells. Following optimisation, these techniques were applied to investigate the activity of bacteria exposed to disinfection, both in the laboratory and in real systems. Raw and potable waters from various locations around South Australia were then analysed to investigate relationships between numbers of active bacteria and those detected by traditional culture-based techniques. Flow cytometric cell sorting of active bacteria followed by 16S rRNA gene-directed PCR and denaturing gradient gel electrophoresis (DGGE) was then used to track the survival of bacteria through water treatment and into distribution. In doing so the identification of active bacteria not detected by culture was achieved. Finally, real-time PCR was optimised for detection of ammonia oxidising bacteria. This group of bacteria were responsible for loss of disinfection residual within a chloraminated distribution system. / thesis (PhD)--University of South Australia, 2005.

There is much debate on the carcinogenic potential of disinfection by-products (DBP) in chlorinated water supplies. Until recently, epidemiological studies have been limited in their ability to examine accurately the risk of cancer with exposure to environmental carcinogens. This has largely been due to the long latency periods associated with cancer development, and the difficulties in accurately estimating chronic exposure. Although there is evidence, from predominantly case-control studies, of increased bladder cancer with exposure to chlorinated water supplies, the evidence is inconclusive. ¶ In an attempt to determine the carcinogenic potential of trihalomethanes (THMs) in chlorinated water, this study utilises DNA damage to bladder cells, evident as micronuclei, as a pre-clinical outcome measure. Using a pre-clinical marker helps overcome some of the limitations associated with long latency periods. The study improves on previous studies by estimating exposure to DBP at an individual level, and takes into consideration ingestion, inhalation and dermal exposure. ¶ A cohort study was undertaken in three Australian communities. The Bungendore (NSW) water supply was not chlorinated thereby providing a community unexposed to DBPs from chlorinated water. Canberra (ACT) and Adelaide (SA) had intermediate and relatively higher (but still within NHMRC guideline levels) of DBPs in the reticulation system. Trihalomethane levels in reticulated water (external dose) and in urine (internal dose) were used as exposure indices. As well, intake dose was computed by adjusting external dose for individual variations in ingestion and bathing. The primary outcome measure was the prevalence of micronuclei in bladder epithelial cells. A DNA index derived from flow cytometry was also used to estimate DNA damage in bladder cells. Associations between exposure and outcome were estimated using Poisson regression models, having identified and adjusted for interaction effects and confounders. ¶ A total of 529 participants were eligible to participate, of which 348 (65.8%) completed all aspects of the study. Analysis was limited to the 228 participants (65.53% of those who completed the study) who had slides suitable for micronuclei scoring. One hundred and forty three (63%) of the 228 participants were from the exposed communities, while 85 (37%) were from the unexposed community. This sample exceeded the estimated 50 per group required to detect a relative risk of 1.4, with a significance level of 0.05 and 80% power. ¶ External dose for total THM for the two chlorinated (exposed) communities ranged from 37.75 to 157.25 mg/l. Intake dose estimated by fluid intake diary ranged from 2.9 to 469.5 mg/l, while a retrospective questionnaire estimated intake dose to range from 0 to 409.4 mg/l. Internal dose (urine levels) of total THM for the same two communities ranged from 0 to 6.82 mg/l. Adjusted risk estimate for DNA damage to bladder cells (using the micronuclei assay) when total THM was assessed by available dose was 1.0002 (0.997 to 1.003), by intake dose estimated by fluid intake diary was 1.0001 (0.998 to 1.002), by intake dose estimated by questionnaire was 1.001 (0.999 to 1.003), and by internal dose was 1.05 (0.89 to 1.24). Using DNA index from flow cytometry as the outcome measure also did not identify significant associations, except when exposure was assessed as available dose of total THM (RR=1.0042; 1.0003 to 1.0081). ¶ The results suggest that THM levels are not significantly associated with DNA damage to bladder cell. This supports suggestions of THMs being non-genotoxic. Further work is required to assess the relationship between THM and the more mutagenic compounds, and to assess the carcinogenicity of the more mutagenic compounds at concentrations occurring in drinking water.

Microbial Reduction on Eggshell Surfaces by the use of Hydrogen Peroxide and Ultraviolet Light. (August 2011) Steven Michael Gottselig, B.S., Texas A&M University Chair of Advisory Committee: Dr. Craig Coufal The effect of hydrogen peroxide (H2O2) in combination with ultraviolet light (UV) as an egg sanitization process on eggshell surfaces was studied. Preliminary experiments were conducted to develop an optimized methodology for eggshell disinfection that will be an effective and efficient way to reduce microorganisms on hatching eggs. Several experiments were conducted to reduce the natural flora found on the eggshell surface. Hatching eggs were collected from White Leghorn hens housed in floor pens with nest boxes. Eggs had no adhering organic material present. Results from these experiments led to the modification of the prototype equipment as well as the treatment application methodology. Following the experiments to optimize the methodology for H2O2 spraying and UV exposure time, the methodology was applied to eggs inoculated with Salmonella Typhimurium. Eggshell crush and rub methodology was used to enumerate bacteria within the pores and membranes of the egg. The optimized H2O2 and UV combination treatment process was then applied to commercial broiler breeder hatching eggs to evaluate the effects on hatchability. Based on the parameters tested, results indicate that two applications of 3% H2O2 followed by 5 sec of UV exposure after each application produced the most consistent microbial reductions on eggshells. To enhance these effects, the addition of a 180° rotation between the two applications showed to be effective at further reducing the natural flora found on the eggshell surface. Studies using this optimal methodology on eggs inoculated with Salmonella at 9 log10 CFU/egg yielded greater than 5 log10 CFU/egg reductions. However, this methodology had little to no effect on reducing bacteria found within the pores and membranes of the eggs inoculated with Salmonella. These findings indicate that the effects of the disinfection process are largely limited to the eggshell surface. Hatch studies showed significant reductions in eggshell microbial levels under field conditions with eggs having large amounts of organic material present on the shell surface. Hatchability was maintained after treatment when compared to untreated eggs. Additional studies are needed to develop advanced equipment to apply this technology under commercial conditions.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

There has been a recent surge in the number of people using reclaimed water systems for personal use. Because of this, it is getting more and more important for easy-to-use and cost effective disinfectants on the market for consumer application. This study looked at the efficacy of three disinfectants, trichloromelamine, ozone and acetic acid, for their ability to reduce the number of waterborne pathogens. Four samples of TCM were tested in a 10mL contaminated water:1mL TCM solution ratio and plated for both total plate counts and to check for generic E.coli. It was found that one of the four samples of TCM (TCM 3) was able to not only give a percent reduction of 92.54%, but it also killed the E.coli that was present in the water. TCM1 had an average percent reduction of 98.77, TCM2's percent reduction was 97.34, and TCM4's: 87.64. This was not the most effective disinfectant, however. Similar tests were done with ozone, ozone that was mixed with brine water, and ozone that was mixed with acetic acid, as well as pure acetic acid. Ozonated brine water, and ozone mixed with acetic acid were both nearly 100% effective at reducing bacterial load in the water samples (99.989 and 100%, respectively). The pure ozone was not nearly as effective, with a percent reduction of 85.7%. These results indicate that TCM and ozone could possibly be effective tools for the consumer to use to disinfect water holding tanks, however, more testing needs to be done in order to find out exactly how effective these products are in the long term, as well as to find the contact time needed for effective kill by TCM.

No description available.

Chlorine is the primary method for disinfection of drinking water in the United States; however, growing concerns about the potential hazards associated with carcinogenic chlorine disinfection by-products have resulted in increased efforts to develop alternative methods of water disinfection. In addition, it is sometimes difficult to maintain an adequate concentration of free chlorine throughout a drinking water distribution system due to intrusion events and the presence of biofilms.Silver and copper are widely used as environmental biocides and as clinical antimicrobial agents. Copper has been extensively used as an algaecide for many years, and is reported to be one of the most toxic metals to heterotrophic bacteria in aquatic environments. In this study, silver and copper, both individually and in combination, were able to significantly reduce the numbers of the bacterial pathogens Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, and Mycobacterium fortuitum in aqueous solutions. Silver and copper together could potentially be used as a secondary disinfectant in water treatment because their residual effect is long lasting and no harmful byproducts are generated.Besides water, produce can also be a source of microbial pathogens. Fruits and vegetables are the third leading source in microbial foodborne outbreaks, accounting for more than 10,000 cases of foodborne illness in the U.S. between 1990 and 2001. Alternative produce sanitizers in addition to chlorine were evaluated against foodborne pathogens inoculated onto lettuce. Overall, Fit® (citric acid, grapefruit oil extract) and chlorine yielded the greatest reductions of the study organisms.A large number of compounds are available for use as disinfectants; however, some are highly toxic, corrosive and produce harmful by-products. Natural antimicrobial products are another possible alternative. The efficacy of a natural peptide-based antimicrobial, Absolute Fx, was assessed against bacteria and viruses. Absolute Fx effectively inactivated the study organisms.

The first study was designed to determine the occurrence of bacteria in dishcloths used in restaurants and bars. Coliforms were isolated from 89% of dishcloths and 70% of tabletops. Escherichia coli was isolated from 54% of dishcloths and 20% of tabletops. The numbers of heterotrophic bacteria (HPC) and coliforms were higher in bars than in restaurants. The levels of HPC found in dishcloths were 25-fold and coliforms were 60-to 120-fold lower than the levels found in dishcloths in previous home studies. The most commonly isolated genera from dishcloths in restaurants and bars differed from those in homes. The numbers of HPC on restaurant tabletops were 45-fold greater after cleaning than prior to cleaning. The mandatory use of sanitizers in restaurants and bars may therefore have reduced contamination levels and caused a shift in the microbial populations present in food service establishments. The second study was designed to determine the recovery efficiency and the survival of two respiratory viruses on produce and was compared to the survival of the enteric poliovirus 1. Adenovirus was recovered with an efficiency of 56%, 32% and 35% from lettuce, strawberries and raspberries, respectively. Coronavirus was recovered from lettuce with an efficiency of 19.6%, but could not be recovered from strawberries. Poliovirus was recovered from lettuce with an efficiency of 76.6% and 0.06% from strawberries. The survival of the viruses was observed for up to eight days. Adenovirus survived the longest on raspberries, with a log₁₀ reduction of 0.61, followed by 1.68- and 1.75-log₁₀ reductions on strawberries and lettuce, respectively. Coronavirus declined by 0.41-log₁₀ after two days and >1.34 log₁₀ by day 4 on lettuce. The enteric poliovirus 1 survived longer on produce, decreasing by only 0.37-log₁₀ on lettuce and 1.30-log₁₀ on strawberries. A microbial risk assessment was performed to assess the risk of infection from ingesting 1, 10, and 100 particles of adenovirus on lettuce. The estimated risk of infection by ingesting these numbers were 1:2000, 1:200, and 1:20, respectively and increased in a proportional way as the number of servings was increased from one to ten and 365 servings of lettuce.