Organic acid based sanitizers and free chlorine to improve the microbial quality and shelf-life of sugar snaps

A screening in a sugar snap packaging company showed a converged build-up of aerobic psychrotrophic plate count (APC) (ca. 6.5 log CFU/100 mL), yeasts and molds (Y&M), and lactic acid bacteria (LAB) (both ca. 4.5 log CFU/100 mL) in the wash water in the absence of water sanitizer, and a low build-up of chemical oxygen demand (30 ± 5 mg O₂/L) and turbidity (5.2 ± 1.1 NTU).     

Preliminary observations of a continuous flow solar disinfection system for a rural community in Kenya

This project involves the design and installation of a continuous flow reactor which uses solar radiation, an abundant resource in most sub-Saharan countries, to disinfect water supplies. The system was installed at a rural village in Kenya to disinfect surface water collected at a recently constructed micro-dam. The solar reactor uses CPC reflectors which reflect both direct and diffuse solar radiation onto clear pipes through which the requisite water supply flows. The reaction kinetics for the full-scale design had been determined on a variety of pathogenic micro-organisms under both artificial and real sunlight in controlled conditions. The community fully participated in the planning, installation and subsequent operation of the system. The preliminary water quality results indicate that the system is providing a safe source of water for the community. The installation, commissioning and initial use of the system highlights the critical need for community involvement and approval if such interventions are going to be successful in rural areas, alongside the requirements for strategic and technical support.     

Solar disinfection of wild Salmonella sp. in natural water with a 18 L CPC photoreactor: Detrimental effect of non-sterile storage of treated water

For the first time solar disinfection of liters of water containing wild Salmonella sp. and total coliforms was carried out in a compound parabolic collector (CPC) photoreactor at temperatures of almost 50 °C. Using surface water with high turbidity, this treatment was efficient in completely inactivating Salmonella sp. without regrowth during the subsequent 72 h of dark sterile storage. However if the solar treated water is poured in a non- sterile container, bacteria regrowth occurs even if 10 mg L⁻¹ of H₂O₂ is added before the storage. On the other hand, 30 mg L⁻¹ of H₂O₂ added when the irradiation started was completely depleted within 2 h and did not prevent bacterial regrowth during post-irradiation storage in non-sterile containers, demonstrating that storage of large volumes of water treated by solar irradiation was not optimal. Finally, total coliforms (Escherichia coli included) showed a far higher sensitivity than Salmonella sp. and demonstrated to be an inappropriate indicator for monitoring bacterial contamination in water during solar disinfection processes.     

社区医院污水处理系统改造方案实施

针对某社区医院医疗污水排放不达标的问题,采用生物接触氧化、组合沉淀、消毒、脱氯等工艺对医院医疗污水处理系统进行改造实施。经一年多的运行证明该改造方案处理效果稳定且耐冲击力较强,可见此工艺处理医疗污水是可行的。     

关于餐馆消毒柜使用的经济学分析

目前,消毒柜是众多餐馆的必备消毒设备之一。但调查显示,由于使用成本等方面的原因,部分消毒柜往往成为摆设,没有起到应有的作用。文章从经济学角度对餐馆消毒柜使用问题进行分析。     

Greywater treatment and reuse results from a 50-person trial

The paper describes a seven year project to develop a greywater treatment plant for lavatory flushing. Site surveys and laboratory research was used to produce a design for a 50-person residential University hall. The final design included a balancing tank (13:1 peak to average capacity) screening (5 mm), a moving bed bioreactor and alternating deep bed double filtration (reticulated foam). The plant achieved a recycled water quality of 3 mg/l biochemical oxygen demand (BOD) (used as an indicator of odour potential and regrowth) a water clarity of 2 nephelometric turbidity units (NTU) and 2 mg/l suspended solids. Ultra violet (UV) disinfection was added to meet the UK guidelines of zero microbial indicator organisms. The demonstration trial lasted 5 years and users were unable to differentiate between the recycled water and mains water in the blind trial.     

The occurrence of perchlorate during drinking water electrolysis using BDD anodes

Electrochemical studies were carried out to estimate the risks of perchlorate formation in drinking water disinfected by direct electrolysis. Boron Doped Diamond (BDD) anodes were used in laboratory and commercially available cells at 20 °C. The current density was changed between 50 and 500 A m⁻². For comparison, other anode materials such as platinum and mixed oxide were also tested. It was found that BDD anodes have a thousandfold higher perchlorate formation potential compared with the other electrode materials that were tested. In long-term discontinuous experiments all the chloride finally reacted to form perchlorate. The same result was obtained when probable oxychlorine intermediates (OCl⁻, ClO₂⁻, ClO₃⁻) were electrolysed in synthetic waters in the ppm range of concentrations. The tendency to form perchlorate was confirmed when the flow rate of drinking water was varied between 100 and 300 L h⁻¹ and the temperature increased to 30 °C. In a continuous flow mode of operation a higher chloride concentration in the water resulted in a lower perchlorate formation. This can be explained by reaction competition of species near and on the anode surface for experiments both with synthetic and local drinking waters. It is concluded that the use of electrodes producing highly reactive species must be more carefully controlled in hygienically and environmentally oriented applications.     

BDD anodic oxidation as tertiary wastewater treatment for the removal of emerging micro‐pollutants,pathogens and organic matter

This work reports for the first time the removal of 17α‐ethynylestradiol (EE2), a synthetic estrogen hormone, from secondary treated effluents by electrochemical oxidation. Experiments were conducted in a single compartment reactor comprising a boron‐doped diamond (BDD) anode and a zirconium cathode. EE2, in the range 100–800 µg L^?1, was spiked in the post‐chlorination effluent of a municipal treatment plant and oxidized at 0.9–2.6 mA cm^?2 current density. Complete degradation of 100 µg L^?1 EE2 was achieved in 7 min at 2.1 mA cm^?2 and inherent conditions, while the addition of 0.1 mol L^?1 NaCl achieved removal in just a few seconds. The process was then tested in the pre‐chlorination effluent at 2.1 mA cm^?2 and inherent conditions; complete E. coli killing and EE2 removal occurred in just 1.5 and 3.5 min, respectively, while overall estrogenicity (assessed by the YES assay) and residual organic matter (in terms of chemical oxygen demand (COD)) decreased by 50% and 85% after 30 min, respectively. These results clearly show the potential of BBD electrochemical oxidation to serve as an efficient tertiary wastewater treatment. Copyright © 2011 Society of Chemical Industry