Damage mechanisms of pathogenic bacteria in drinking water during chlorine and solar disinfection

This study aimed at elucidating the inactivation mechanisms of pathogenic bacteria in drinking water during chlorine and solar disinfection using a simple plating method. The well-known bacterial model Escherichia coli was used as pathogenic bacteria for the experiments. The damage mechanisms of E. coli were evaluated by simple plating method on selective, less selective and non-selective media. Results showed that, injured E. coli were detected at different levels during chlorine and solar disinfection. The use of selective media during water quality control showed effectively the destruction of E. coli during solar disinfection while the removal of E. coli during chlorine disinfection was not ensured. The damage of cell components and/or metabolic functions showed that there is a primary and mainly damage of E. coli during chorine and solar disinfection. Chlorination firstly and mainly damaged membrane cell followed by that of enzymatic functions and nucleic acid; while solar disinfection damaged mainly nucleic acid. The use of simple plating method in water quality control is limited by the choice of plating media depending on the disinfectant used. The understanding of the damage mechanisms of pathogenic bacteria cells during disinfection helps improve drinking water quality control and develops more effective disinfection strategies.© 2016 International Formulae Group. All rights reserved.Keywords: Drinking water, pathogenic bacteria, E. coli, damage mechanisms, chlorine disinfection, solar disinfectio

Microfiltration, Nano-filtration and Reverse Osmosis for the Removal of Toxins (LPS Endotoxins) from Wastewater

Lipopolysaccharide (LPS) endotoxin, a bacterial byproduct abundantly present in wastewater, is more and more representing a major concern in wastewater treatment sector for the potential health risk it represents. It is, therefore, more urgent than before to protect consumers from contaminating their fresh potable water reserves with LPS endotoxin through aquifer replenishment using reclaimed wastewater or by supplying reclaimed wastewater as potable water. Membrane treatment is an alternative to activated sludge process and is the most commonly used to treat wastewater. Moreover, nano-filtration and reverse osmosis are the most advanced technologies used to treat wastewater to a potable level. Removal efficiency of LPS endotoxin using Membrane bioreactors (MBRs) and Nanofiltration (NF) and Reverse Osmosis (RO) is subject of this paper. It revealed that these advanced technologies could remove a significant amount of endotoxin. However, levels of concentration in the product water are still much higher than the one found in tap water and it is not advisable to supply this water directly to consumers. Further investigations are required to determine the best management practices for a safe supply of potable water from reclaimed wastewater

Design and operation of the bio-toilet system

Criteria for the proper design and operation of the bio-toilet have not been established either by the manufacturers or by the authorities. Based on the results of experimental research already reported by us, criteria for the proper design and operation of the bio-toilet system were established. The establishment of operation criteria led to the formulation of an operation scheme where three main zones are distinguished: i) green zone, where the best composting performance is expected; ii) yellow zone, where biodegradation can be conducted but performance is not the most efficient; iii) other zones where operation of the bio-toilet is not recommended because odour problems and human health risks will develop, or in the worst case, biodegradation of faeces will not occur. In the design criteria, the surface area required for evaporating the water loads due to contributions of urine and faeces was determined by applying concepts of drying theory. This theory was also applied to estimate the mass and volume of dried sawdust required for dealing with the critical water loading. However, the accumulation of stabilised solids transpired to be more critical and, finally, mass and volume of dried sawdust were estimated based on this factor

Production of slow-released nitrogen fertilizer from urine

Human excreta, especially urine is rich in nitrogen that can be utilized for agricultural purposes, while the slow-release fertilizer allows effective utilization of nutrients in agricultural production. The direct formation of slow-release fertilizer - methylene urea - from urine was being proposed in this study. The experiments were tried to prove formation of methylene urea from human urine, and to investigate the effect of pH and salt concentration on the reaction rate. The synthetic urine and real urine were used for the urea source of the reaction. As a result, the precipitates were prepared from synthetic urine, while the small molecule fractions generated then they grew into precipitate. The nuclear magnetic resonance, infrared spectroscopy, element analyses showed the precipitates in synthetic urine were the same compound found in the urea solution, which was methylene urea. The reaction rate was high at low pH value. The reaction rate in the buffer solution was lower than the synthetic urine at the same pH, because some salts may work as a catalyst. The urea concentration reduction rate in real urine showed the same trend with synthetic urine at the same pH, while the precipitation was quite similar to methylene urea

SIMULATION ANALYSIS OF UPGRADING THE EXISTING WASTEWATER TREATMENT PLANT FROM A CONVENTIONAL PROCESS TO A MULTI-ANOXIC ZONE PROCESS WITH STEP FEEDING

第6回衛生工学シンポジウム（平成10年11月5日（木）-6日（金） 北海道大学学術交流会館） . 2 モデリング・評価 . 2-

SIMULATION ANALYSIS OF THE EFFECT OF PIPE CONNECTION STYLE ON IN-LINE STORAGE CAPACITY OF A STORM WATER DRAINAGE NETWORK

第6回衛生工学シンポジウム（平成10年11月5日（木）-6日（金） 北海道大学学術交流会館） . 2 モデリング・評価 . P2-