Life Cycle Assessment (LCA) Comparing Disinfection Options for Drinking Water Treatment

Drinking water treatment is essential to obtain a healthy source of water that can be distributed throughout a community. There are various methods to disinfect water, and all have trade-offs regarding public health and the environment. For example, chemical disinfectants that use chlorine can produce disinfection by-products within treated drinking water. The Environmental Protection Agency regulates these disinfection by-products because of their potential to cause cancer. Ultraviolet (UV) light is a physical disinfection method that does not produce these disinfection by-products, which is why it is becoming a preferred method for water treatment. For this research, I conducted a comparative life cycle assessment (LCA) for chemical and physical disinfection methods. The main factors considered within this LCA were energy consumption and human toxicity risk. The results from my research support my original hypothesis that the assessed chemical disinfection method had less energy consumption and a higher human toxicity risk compared to the assessed physical disinfection method. The results show that each method has trade-offs and that this LCA can provide extensive knowledge on which disinfection method would work best for the Bethlehem, New Hampshire community based on the stakeholders’ priorities

AgandCuloadedonTiO2/graphite as a catalyst for �Escherichia coli- contaminated water disinfection

TiO2 film was synthesized by means of the chemical bath deposition (CBD) method from TiCl4 as a precursor and surfactant cetyl trimethyl ammonium bromide (CTAB) as a linking and assem- bling agent of the titanium hydroxide network on a graphite substrate. Ag and Cu were loaded on the TiO2 film by means of electrodeposition at various applied currents. Photoelectrochemical testing on the composite of Ag–TiO2/G and Cu–TiO2/G was used to define the composite for Escherichia coli-contaminated water disinfection. Disinfection efficiency and the rate of disinfection of E. coli-contaminated water with Ag–TiO2/G as a catalyst was higher than that observed for Cu–TiO2/G in all disinfection methods including photocatalysis (PC), electrocatalysis (EC), and photoelectrocatalysis (PEC). The highest rate constant was achieved by the PEC method using Ag–TiO2/G, k was 6.49 × 10−2 CFU mL−1 min−1 . Effective disinfection times of 24 h (EDT24) and 48 h (EDT48) were achieved in all methods except the EC method using Cu–TiO2/G. Keywords: Ag–TiO2/G, Cu–TiO2/G, Escherichia coli, disinfectio

A 10-day vacancy period after cleaning and disinfection has no effect on the bacterial load in pig nursery units

Background: Biosecurity measures such as cleaning, disinfection and a vacancy period between production cycles on pig farms are essential to prevent disease outbreaks. No studies have tested the effect of a longer vacancy period on bacterial load in nursery units. Methods: The present study evaluated the effect of a 10-day vacancy period in pig nursery units on total aerobic flora, Enterococcus spp., Escherichia coli, faecal coliforms and methicillin resistant Staphylococcus aureus (MRSA). Three vacancy periods of 10 days were monitored, each time applied in 3 units. The microbiological load was measured before disinfection and at 1, 4, 7 and 10 days after disinfection. Results: No significant decrease or increase in E. coli, faecal coliforms, MRSA and Enterococcus spp. was noticed. Total aerobic flora counts were the lowest on day 4 after disinfection (i.e. 4.07 log CFU/625 cm(2)) (P < 0.05), but the difference with other sampling moments was limited (i.e. 0.6 log CFU/625 cm(2)) and therefore negligible. Furthermore, this observation on day 4 was not confirmed for the other microbiological parameters. After disinfection, drinking nipples were still mostly contaminated with total aerobic flora (i.e. 5.32 log CFU/625 cm(2)) and Enterococcus spp. (i.e. 95 % of the samples were positive) (P < 0.01); the feeding troughs were the cleanest location (total aerobic flora: 3.53 log CFU/625 cm(2) and Enterococcus spp.: 50 % positive samples) (P < 0.01). Conclusions: This study indicates that prolonging the vacancy period in nursery units to 10 days after disinfection with no extra biosecurity measures has no impact on the environmental load of total aerobic flora, E. coli, faecal coliforms, MRSA and Enterococcus spp.

Development of an ultrasonic resonator for ballast water disinfection

Ultrasonic disinfection involves the application of low-frequency acoustic energy in a water body to induce cavitation. The implosion of cavitation bubbles generates high speed microjets &gt;1 km/s, intense shock wave &gt;1 GPa, localized hot spots &gt;1000 K, and free-radicals, resulting in cell rupture and death of micro-organisms and pathogens. Treatment of marine ballast water using power ultrasonic is an energy-intensive process. Compared with other physical treatment methods such as ultraviolet disinfection, ultrasonic disinfection require 2 to 3 orders of magnitude more energy to achieve similar rate of micro-organism mortality. Current technology limits the amount of acoustic energy that can be transferred per unit volume of fluid and presents challenges when it comes to high-flow applications. Significant advancements in ultrasonic processing technology are needed before ultrasound can be recognized as a viable alternative disinfection method. The ultrasonic resonator has been identified as one of the areas of improvement that can potentially contribute to the overall performance of an ultrasonic disinfection system. The present study focuses on the design of multiple-orifice resonators (MOR) for generating a well-distributed cavitation field. Results show that the MOR resonator offers significantly larger vibrational surface area to mass ratio. In addition, acoustic pressure measurements indicate that the MOR resonators are able of distributing the acoustic energy across a larger surface area, while generating 2-4 times higher pressures than existing ultrasonic probes

Microbiological evaluation of different reprocessing methods for cuffed and un-cuffed tracheostomy tubes in home-care and hospital setting

Background: Manufacturers’ recommendations on cleaning of tracheostomy tubes focus on general warning information and non-specific manual cleaning procedures. The aim of this experimental study was to evaluate different reprocessing methods and to determine the mechanical integrity and functionality of tracheostomy tubes following reprocessing. Methods: Sixteen cuffed or un-cuffed tracheostomy tubes obtained from hospital in-patients were reprocessed using one of the following reprocessing methods: a) manual brushing and rinsing with tap water, b) manual brushing followed by disinfection with a glutaraldehyde solution, c) manual brushing followed machine-based cleaning in a dishwasher, and d) manual brushing followed by ultrasound cleaning in a commercially available ultrasound device. Microbial burden of the tubes before and after reprocessing was assessed by measurement of microbial colony-forming units per mL (CFU/mL) of rinsing fluid. After cleaning, tracheostomy tubes were investigated for loss of functionality. Findings: Manual brushing and rinsing with tap water reduced microbial colonization in average by 102 CFU/mL, but with poor reproducibility and reliability. Complete microbial reduction was achieved only with additional chemical or machine-based thermal disinfection. Ultrasound sonification yielded no further microbial reduction after manual brushing. Conclusion: Manual brushing alone will not result in complete eradication of microorganism colonising cuffed or un-cuffed tracheostomy tubes. However, manual cleaning followed by chemical or thermal disinfection may be regarded as safe and reproducible reprocessing method. If a machine-based reprocessing method is used for cuffed tubes, the cuffs’ ventilation hose must be secured in a safe position prior to thermal disinfection

Heterogeneity in the Relationship between Disinfection By-Products in Drinking Water and Cancer: A Systematic Review.

The epidemiological evidence demonstrating the effect of disinfection by-products (DBPs) from drinking water on colon and rectal cancers is well documented. However, no systematic assessment has been conducted to assess the potential effect measure modification (EMM) in the relationship between DBPs and cancer. The objective of this paper is to conduct a systematic literature review to determine the extent to which EMM has been assessed in the relationship between DBPs in drinking water in past epidemiological studies. Selected articles (n = 19) were reviewed, and effect estimates and covariates that could have been used in an EMM assessment were gathered. Approximately half of the studies assess EMM (n = 10), but the majority of studies only estimate it relative to sex subgroups (n = 6 for bladder cancer and n = 2 both for rectal and colon cancers). Although EMM is rarely assessed, several variables that could have a potential modification effect are routinely collected in these studies, such as socioeconomic status or age. The role of environmental exposures through drinking water can play an important role and contribute to cancer disparities. We encourage a systematic use of subgroup analysis to understand which populations or territories are more vulnerable to the health impacts of DBPs

Evaluating of the disinfection and water quality effects on UV application in the primary stage of water treatment

Background: Irradiation of water by UV has been considered as an attractive alternative for disinfection because its low-impact, pathogen killing capacity shows tremendous promise for meeting today's drinking water regulatory requirements. This study has been performed with the objective of utilizing medium pressure lamp in the preliminary stage of municipal water treatment, namely prior to water clarification and filtration. Methods: Raw water samples were irradiated for 30 s in a lab-scale closed reactor. Disinfection results showed nearly 2 log reduction in HPC for all the samples without formation of nitrite in excess of its MCL. As in a few previous works the formation of nitrite as an objectionable DBP had been reported, this study was extended by preparing synthetic water samples having different amounts of nitrate and turbidities. Results: As far as the initial nitrate concentration dose not exceed 10 mg/L N-NO3, there would be no risk of nitrite increasing in excess of the MCL. Conclusion: Meeting the goal of at least 90 % disinfection for water samples with turbidity levels of as high as 750 NTU is possible by utilizing medium- pressure UV lamp

Model based study of autothermal thermophilic aerobic digestion (ATAD) processes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Engineering and Automation of Massey University

An Autothermal Thermophilic Aerobic Digestion process, or ATAD process, is a relatively new sewage sludge treatment process. The ATAD process has been developed for the disinfection and stabilisation of sewage sludge, which is a by-product of wastewater treatment. The end product can be applied to the land as a soil additive or fertiliser with no restrictions, as the process dramatically reduces public health and environmental risks. The process is comparable to the composting process used for municipal solid waste and garden wastes. The process requires oxygen, usually in the form of air, to be applied to the sludge by an aeration system. The oxygen stimulates an exothermic biochemical reaction, which in turn heats the sludge up to thermophilic temperatures (between 50 and 65°C). At these temperatures the pathogenic bacteria, viruses and parasites in the sludge that are harmful to human health are effectively destroyed. The biochemical reaction also degrades a large portion of the organic sludge, which means that unstable, volatile odour generating substances are removed; this reduces the likelihood of smells and the attraction of flies and rodents (vector attraction) to the sludge.[FROM INTRODUCTION