Interplay of factors involving chlorine dose, turbidity flow capacity and pH on microbial quality of drinking water in small water treatment plants

In an endeavour to ascertain the interplay of factors involving chlorine dose, turbidity and flow capacity on microbial quality of drinking water in small water treatment plants (SWTPs), data from a previous study were analysed.The findings showed that most of the SWTPs were not producing water of safe microbial quality. Fifty one percent (51%) and seventy three (73%) of the SWTPs were below the stipulated limits for residual chlorine in final water and water at the point of use respectively. Current flow capacity was a major determinant of the microbial water quality indicators but no association was found between the dose of chlorine used for water treatment and the microbial water quality indicators. However, a combination of the amount of chlorine dose used up during treatment, flow capacity and change in turbidity contributed to about 65% of the amount of heterotrophic plate counts removed from raw water. Current flow capacity contributed less than 14% of the variation in chlorine dose used in water treatment at the plants. Turbidity tended to correlate and contribute more to the prediction of total coliform counts while faecal coliform counts were determined by current flow capacity and conductivity. Treatment plants with current flow capacity of over 50 Mℓ/d tended to be more efficient in heterotrophic plate count removal.In conclusion, this study noted that most of the SWTPs were using a chlorine dosage that was below the amount required by their respective current flow capacity; possible micro-organism resistance to chlorine and the significant effect of the level of turbidity on the microbial quality of treated water.Keywords: microbial indicators, chlorine dose, current flow capacity, turbidity, water treatment plant

Novel bio-catalytic degradation of endocrine disrupting compounds in wastewater

DATA AVAILABILITY STATEMENT : The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.Against the backdrop of towering ecological health implications of estrogen pollution and the inefficacies associated with cost-intensive treatment techniques, this study recorded the earliest attempt of developing an inexpensive bacterial laccase-based biocatalysts for biodegradation of EDCs (Endocrine disrupting compounds), particularly estrogens. First, a central composite design was used to investigate the interactive effects of pH (6.0–8.0), inoculum size (100–500 U/mL), and copper (Cu) (25–75 mg/L) on laccase activity and estrogen degradation respectively. Thereafter, biocatalysts was synthesized comprising laccase and glass beads or silver impregnated clay granules (SICG), which was further used to treat estrogen infused aquatic matrices under different reaction conditions. Maximum laccase activities and estrogen removal for the two tested laccases were 620 U/mL (85.8–92.9%) and 689.8 U/mL (86.8–94.6%) for Lysinibacillus sp. BP1 and Lysinibacillus sp. BP2, respectively, within 72 h, under conditions of optimal inoculum size and/or Cu concentration. Apart from a higher estrogen removal rate compared to free laccased, the biocatalysts were more resistant to temperature, pH and other environmental perturbations, and had enhanced storage ability and reusability. In comparison to clay, beads had a higher potential for recyclability and were more stable under certain experimental factors such as pH, reuse, and temperature, as well as storage conditions. Immobilized enzymes were able to remove 100% of E2, as well as over 90% of E1 and EE2, in 24 h, indicating that they could be scaled up to benchtop bioreactor levels.NRF SARChI Chair for Water Quality and Wastewater Management and Tshwane University of Technology (TUT).http://www.frontiersin.org/Bioengineering_and_Biotechnologyam2023Chemical Engineerin

Diversity and Antibiograms of Bacterial Organisms Isolated from Samples of Household Drinking-water Consumed by HIV-positive Individuals in Rural Settings, South Africa

Diarrhoea is a hallmark of HIV infections in developing countries, and many diarrhoea-causing agents are often transmitted through water. The objective of the study was to determine the diversity and antibiotic susceptibility profiles of bacterial organisms isolated from samples of household drinking-water consumed by HIV-infected and AIDS patients. In the present study, household water stored for use by HIV-positive patients was tested for microbial quality, and isolated bacterial organisms were analyzed for their susceptibility profiles against 25 different antibiotics. The microbial quality of water was generally poor, and about 58% of water samples (n=270) were contaminated with faecal coliforms, with counts varying from 2 colony-forming unit (CFU)/100 mL to 2.4x104 CFU/100 mL. Values of total coliform counts ranged from 17 CFU/100 mL to 7.9x105/100 mL. In total, 37 different bacterial species were isolated, and the major isolates included Acinetobacter lwoffii (7.5%), Enterobacter cloacae (7.5%), Shigella spp. (14.2%), Yersinia enterocolitica (6.7%), and Pseudomonas spp. (16.3%). No Vibrio cholerae could be isolated; however, V. fluvialis was isolated from three water samples. The isolated organisms were highly resistant to cefazolin (83.5%), cefoxitin (69.2%), ampicillin (66.4%), and cefuroxime (66.2%). Intermediate resistance was observed against gentamicin (10.6%), cefepime (13.4%), ceftriaxone (27.6%), and cefotaxime (29.9%). Levofloxacin (0.7%), ceftazidime (2.2%), meropenem (3%), and ciprofloxacin (3.7%) were the most active antibiotics against all the microorganisms, with all recording less than 5% resistance. Multiple drug resistance was very common, and 78% of the organisms were resistant to three or more antibiotics. Education on treatment of household water is advised for HIV-positive patients, and measures should be taken to improve point-of-use water treatment as immunosuppressed individuals would be more susceptible to opportunistic infections

The impact of disinfection processes on biofilm formation in potable water distribution systems

In this study, surface and ground water were used to evaluate the impact of disinfection processes (chlorination, chloramination, ozonation, UV irradiation and hydrogen peroxide) on bacterial regrowth and bioftlm formation in potable water distribution systems using laboratoryscale units. Disinfection was carried out using disinfectant concentrations which were as close as possible to those used in practise. The parameters that were used to evaluate the bactericidal effectiveness of each disinfectant were coliform bacteria, heterotrophic plate count and total bacteria. Membrane filter and standard spread plate procedures were used to enumerate coliform and heterotrophic plate count bacteria respectively. The epifluorescence direct count involving DAPI was used to enumerate total bacteria. The scanning electron microscopy technique was used to visualize biofilm formation on stainless steel and cement coupons. The microbial disinfection efficacy of all disinfectants was found to be equal in the elimination of coliform bacteria in surface water although recovery of coliforms occurred 24 h after disinfection in all treated water systems with the exception of chloraminated water systems. For the groundwater, all disinfectants were found to remove coliform bacteria within the first hours of disinfection with the exception of hydrogen peroxide. Complete removal of coliform bacteria by hydrogen peroxide occurred only 48 h after disinfection. In surface water systems, more than 99 % (average kill percentage) of heterotrophic bacteria were removed by all the disinfection processes. Chloramination and hydrogen peroxide disinfection, however, resulted in a higher effective disinfection (average 99.99 %) although a longer period of time (between 24 and 72 h for chloramination and 72 h for hydrogen peroxide) was required to achieve this kill percentage. In groundwater systems, more than 99.90 % (average kill percentage) heterotrophic bacteria were removed by all the disinfectants with the exception of hydrogen peroxide (99.88 % average kill percentage). However, ozone was highly effective within the first 2 has shown by the average kill percentage of 99.999 % of heterotrophic bacteria. These results led to the conclusion that the microbial disinfection efficacy was greater when using groundw~ter than when using surface water. The phenomenon of bacterial regrowth was linked to the absence of concentrations of disinfectant residuals. In both water sources, bacterial regrowth occurred earlier in chlorinated, ozonated and UV treated water than in chloraminated and hydrogen peroxide treated water. Significantly higher heterotrophic bacteria counts were noted in chlorine, ozone and UV treated waters than either in chloramine or hydrogen peroxide treated waters. The greater persistence of monochloramine and hydrogen peroxide residuals was found to inhibit bacterial regrowth in both test waters.Thesis (PhD)--University of Pretoria, 1997.tm2015Microbiology and Plant PathologyPhDUnrestricte

Kinetics of petroleum oil biodegradation by a consortium of three protozoan isolates (Aspidisca sp., Trachelophyllum sp. and Peranema sp.)

Petroleum oil is a complex mixture of substances, the majority of which are hydrocarbons; the latter represent an extremely important and heterogeneous group of compounds that find their way into water resources by anthropogenic or natural ways. The majority of toxic hydrocarbon components of petroleum are biodegradable, where bioremediation using microbial species has become an integral process for the restoration of oil-polluted areas. In this study, three bioremediation processes, namely natural attenuation, nutrient supplementation by adding glucose and biostimulation by adding Tween® 80, were carried out in various petroleum hydrocarbon concentrations in polluted water media using a consortium of three protozoan isolates (Aspidisca sp., Trachelophyllum sp. and Peranema sp.). A first-order kinetics model was fitted to the biodegradation data to evaluate the biodegradation rate and to determine the corresponding half-life time. First-order kinetics satisfactorily described the biodegradation of the petroleum-based contaminants under abiotic conditions. The results showed an increase in the percentage removal of petroleum oil at the lower petroleum concentrations and a gradual percentage decrease in removing petroleum oil residues occurred when there was an increase in the initial concentrations of the petroleum oil: 39%, 27%, 22%, 12%, 10% for various petroleum oil concentrations of 50, 100, 150, 200, 250 mg/L, respectively. A similar trend was also observed in the glucose-supplemented culture media where the reduction was 45% and 78% for petroleum concentrations of 250 mg/L and 50 mg/L, respectively. Biodegradation of between 33 and 90% was achieved at a Tween® 80 concentration of between 50 mg/L and 250 mg/L. The degradation rate constants for the natural attenuation process ranged between ≥0 to ≤0.50, ≥0 to ≤0.35, ≥0 to ≤0.25, ≥0 to ≤ 0.14 and ≥ 0 to ≤0.11 for petroleum oil concentrations varying from 50, 100, 150, 200 and 250 mg/L, respectively, during the study after 30 days. In the presence of glucose as a nutrient supplement, the degradation rate constants increased from 0 day−1 to 0.8 day−1 when exposed to the lowest oil concentration of 50 mg/L, while the lowest rate constants (from 0 day−1 to 0.25 day−1) were observed at the highest petroleum oil concentration of 250 mg/L for the same period. Overall enhancement of the degradation rates was achieved when adding the Tween® 80 surfactant compared to the first two biodegradation processes. The longest half-life was achieved after 217 days during the natural attenuation process for samples with an oil concentration of 250 mg/L and this was reduced to 85 days using the glucose-supplemented process. There was a further decrease to 45 days when Tween® 80 surfactant was added during the biostimulation process. The highest efficiency of ≥20% of Tween® 80 was observed between 6 and 18 days and thereafter it decreased slightly to ≤20%

The relationship of biomass to phosphate uptake by Acinetobacter junii in activated sludge mixed liquor

The involvement of Acinetobacter in biological excess phosphate removal from the activated sludge process is widely accepted, though its role is not yet clearly defined. To better understand why activated sludge systems remove phosphate, different cell concentrations of Acinetobacter junii were used as inoculum in a mixed liquor medium containing sodium acetate. The phosphate uptake capacity was dependent on the biomass concentration. Low initial biomass concentrations triggered the release of phosphate once transferred into the mixed liquor. Release of phosphate increased during active growth and uptake occurred when cells reached the stationary growth phase. High initial biomass concentration of Acinetobacter junii resulted in uptake of phosphate during the entire duration of the experiment leading eventually to complete phosphate removal

Diversity and Antibiograms of Bacterial Organisms Isolated from Samples of Household Drinking-water Consumed by HIV-positive Individuals in Rural Settings, South Africa

Diarrhoea is a hallmark of HIV infections in developing countries, and many diarrhoea-causing agents are often transmitted through water. The objective of the study was to determine the diversity and antibiotic susceptibility profiles of bacterial organisms isolated from samples of household drinking-water consumed by HIV-infected and AIDS patients. In the present study, household water stored for use by HIV-positive patients was tested for microbial quality, and isolated bacterial organisms were analyzed for their susceptibility profiles against 25 different antibiotics. The microbial quality of water was generally poor, and about 58% of water samples (n=270) were contaminated with faecal coliforms, with counts varying from 2 colony-forming unit (CFU)/100 mL to 2.4x104 CFU/100 mL. Values of total coliform counts ranged from 17 CFU/100 mL to 7.9x105/100 mL. In total, 37 different bacterial species were isolated, and the major isolates included Acinetobacter lwoffii (7.5%), Enterobacter cloacae (7.5%), Shigella spp. (14.2%), Yersinia enterocolitica (6.7%), and Pseudomonas spp. (16.3%). No Vibrio cholerae could be isolated; however, V. fluvialis was isolated from three water samples. The isolated organisms were highly resistant to cefazolin (83.5%), cefoxitin (69.2%), ampicillin (66.4%), and cefuroxime (66.2%). Intermediate resistance was observed against gentamicin (10.6%), cefepime (13.4%), ceftriaxone (27.6%), and cefotaxime (29.9%). Levofloxacin (0.7%), ceftazidime (2.2%), meropenem (3%), and ciprofloxacin (3.7%) were the most active antibiotics against all the microorganisms, with all recording less than 5% resistance. Multiple drug resistance was very common, and 78% of the organisms were resistant to three or more antibiotics. Education on treatment of household water is advised for HIV-positive patients, and measures should be taken to improve point-of-use water treatment as immunosuppressed individuals would be more susceptible to opportunistic infections

Evaluation of the impact of disinfection processes on the formation of biofilms in potable surface water distribution systems

In this study, surface water was used to evaluate the impact of disinfection processes (chlorination, chloramination, ozonation, UV irradiation and hydrogen peroxide) on biofilm formation in potable water distribution systems. Biofilm formation was obvious, even in the presence of residual disinfectant concentrations (16.5 mg/l hydrogen peroxide, 1/10 mg monochloramine, 0.2 mgH free chlorine) within the first day after disinfection in the laboratory scale unit. The yield in viable count was higher on stainless steel coupons than on cement coupons within the first 8 days. Viable bacteria numbers on cement coupons were similar (±2 log cfu/sq cm) in chlorinated, ozonated and in the control. Biofilm formation was related to the depletion of residual disinfectant concentration. Monochloramine and hydrogen peroxide had a longer residual effect controlling growth of biofilm cells in the system for a longer period before regrowth occurred. Once no residual concentrations could be detected there was no significant difference between the viable bacterial counts on any of the coupons in the various systems

Examination of the behaviour of Escherichia coli in biofilms established in laboratory-scale units receiving chlorinated and chloraminated water

Groundwater was treated with chlorine and chloramine to study the incorporation and survival of Escherichia coli in developing biofllms in laboratory-scale units. Membrane filter and standard spread plate procedure were used to enumerate coliform and heterotrophic plate count bacteria respectively. Within 96 h the adhesion of heterotrophic plate count bacteria on stainless steel coupons was obvious in all systems, with a higher number of organisms (4 log cfu cm sq) noted for the non-disinfected water. Attachment of E. coli added 24 h after the formation of young biofllms was obvious on stainless steel coupons exposed to the non-disinfected water (9 cfu cm sq) and chlorinated water (2 cfu cm sq). A significant difference between E. coli counts in the non-disinfected water and chloraminated water, and the chlorinated and chloraminated water, was found. However, the ANOVA test indicated no significant difference in E. coli counts for the non-disinfected water and chlorinated water. This investigation revealed the effectiveness of chloramine in preventing the attachment of E. coli in developing biofilm

An overview of biofilm formation in distribution systems and its impact on the deterioration of water quality

The impact of biofilms present in water distribution systems on the microbial quality of potable water is reported in this review. The issues covered include the composition of biofilms, factors governing their formation and the effect and significance of biofilms on the microbial quality of drinking water. The review addresses the main factors governing the formation of biofilms such as the types of disinfectants and residual concentrations, resistance of bacteria to disinfectants, the influence of piping material and the effect of temperature. Methods for the enumeration of bacteria in biofilms as well as emerging technologies for in situ monitoring of biofilms are discussed. Suggested control measures for managing and controlling the problem of biofilm formation in potable water distribution systems to ensure potable water of an acceptable microbiological quality are dealt with