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Water Treatment and Purification
Published in P.K. Tewari, Advanced Water Technologies, 2020
Measurement and monitoring of the chemical substances and contaminants present in water are important. Contaminants, such as pathogens, are difficult to monitor in the field. Most of the time, water quality is measured in terms of indicator organism, which can be easily tested. The most common ones used are total coliforms, fecal coliforms and E. coli. Turbidity is another common measure, as bacteria tend to stick to suspended particles. It is a good indicator of bacteria and is easily measured. WHO has issued guidelines for each of the indicator organisms (Table 6.3). Table 6.4 gives possible inferences from testing for indicator organism E. coli.
E. coli inactivation during excreta digestion in single-stage and two-stage systems
Published in Joy Nyawira Riungu, Off-Site Enhanced Biogas Production with Concomitant Pathogen Removal from Faecal Matter, 2021
The E. coli removal in the two stage co-digestion reactors, applying a UDDT-FS:OMW ratio of 4:1 and 12% TS (Section 3.2.2), showed an 8.0 log inactivation, whereas only a 5.7 log inactivation was achieved in the single stage co-digestion reactor at 12% TS. Results indicate that the two-stage reactor is about 200 times more effective in removing the E. coli indicator organism.
Indicator organisms and the coliform concept
Published in Cara Gleeson, Nick Gray, The Coliform Index and Waterborne Disease, 1996
To be of value as an assessor of faecal contamination, indicator organisms should satisfy the following criteria: They should be a member of the normal intestinal flora of healthy people.They should be exclusively intestinal in habitat and therefore exclusively faecal in origin if found outside the intestine.Ideally they should only be found in humans.They should be present when faecal pathogens are present and only when faecal pathogens are expected to be present.They should be present in greater numbers than the pathogen they are intended to indicate.They should be unable to grow outside the intestine with a die-off rate slightly less than the pathogenic organism.They should be resistant to natural environmental conditions and to water and wastewater treatment processes in a manner equal to or greater than the pathogens of interest.They should be easy to isolate, identify and enumerate.They should be non-pathogenic (Feacham et al., 1983; Oliveri, 1982). The concentration of indicator organisms should be related to the extent of faecal contamination and by implication to the concentration of pathogens and the incidence of waterborne disease (Pipes, 1982a). There is no absolute correlation between the numbers of the indicator organism present and the actual presence or numbers of enteric pathogens. The finding of an indicator organism in a properly treated water indicates the presence of material of faecal origin and thus the potential of contamination.
Flow cytometric assessment of the chlorine/chloramine efficacy of particle-associated bacteria in drinking water
Published in Environmental Technology, 2022
Weiying Li, Yue Li, Feng Wang, Sheng Chen, Jiping Chen
The aim of this study was to determine if there were protective effects when particles without-disinfectant demand co-exist with bacteria in chlorine/chloramine disinfection. Two inorganic substances iron trioxide (Fe2O3) and kaolin clay were selected as representative no-disinfectant demand particles from water sources and distribution systems. Staphylococcus aureus (S. aureus, ATCC 6538) and Escherichia coli (E. coli, ATCC 25922) were chosen as routinely measured fecal indicator organism and opportunistic pathogen related to microbial safety of drinking water. The two bacteria and two particles were built into four PAB systems to explore the effects of particles impacting chlorine/chloramine inactivation. Further, the factors impacting disinfection including particle types, particle size, turbidity and the combination states of different PAB systems were also discussed to offer knowledge of the resistance of PAB for the related practitioners.
Fit-for-purpose urban wastewater reuse: Analysis of issues and available technologies for sustainable multiple barrier approaches
Published in Critical Reviews in Environmental Science and Technology, 2021
Nowadays, ozone or ultraviolet radiation (UV) are among the most commonly applied disinfection technologies. Both have been proven effective but are affected by high investment and operational (energy) costs, and complex O&M. Ozone is an unstable compound and must be generated onsite. UV efficacy, on the other hand, is strongly affected by solution turbidity. Table 7 summarizes indicative log removal values (x-log indicates 10x times reduction of initial parameter value) of pathogen and indicator organism for some mainstream water treatment technologies under optimal operating conditions (DAWR, 2006).
Evaluation of pressurised carbon dioxide pre-treatment aimed at improving the sanitisation and anaerobic digestibility of co-settled sewage sludge
Published in Journal of Environmental Science and Health, Part A, 2019
Maryam Mushtaq, Charles J. Banks, Sonia Heaven
The detrimental effect of pressurized carbon dioxide (P CO2) on bacterial growth was first reported by Valley and Rettger,[9] but it is only over the last two decades that P CO2 has become established as a technique for non-thermal sterilisation,[10] its application to date, however, has been largely confined to the food industry. The principle of P CO2 treatment is that CO2 dissolves in the aqueous phase of a liquid to form carbonic acid (H2CO3), which diffuses into any microbial cells present. This causes a drop in intracellular pH,[11] which affects the enzymatic activities[12] and triggers a series of complex interrelated processes leading to the loss of cell viability.[10] The effect is augmented when pressure is released as CO2 dissolved in the cytoplasm expands causing the microbial cells to rupture and release their contents.[13] The potential benefit in AD is that this cell rupturing process will make the feed biosolids more readily available to anaerobic bacteria, thereby helping to overcome the rate-limiting hydrolysis step of AD.[8] The process could therefore boost biogas production with the additional benefit of potentially enhancing digestate sanitisation through inactivation of pathogenic bacteria.[8] The present evaluation used the P CO2 pretreatment on co-settled SS, a mixture of settled solids from wastewater and the excess biosolids from activated sludge treatment, which was then fed to a mesophilic anaerobic digester. Any potential for improvement in process performance was monitored with reference to biogas production and removal of Escherichia coli as a pathogen indicator organism.