Barry J Lloyd

Progress in the development and use of ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment

This paper reviews the progress in preparing and using ferrate(VI) salt as an oxidant and coagulant for water and wastewater treatment. The literature revealed that due to its unique properties (viz. strong oxidizing potential and simultaneous generation of ferric coagulating species), ferrate(VI) salt can disinfect microorganisms, partially degrade and/or oxidise the organic and inorganic impurities, and remove suspended/colloidal particulate materials in a single dosing and mixing unit process. However, these findings have not yet lead to the full-scale application of ferrate(VI) in the water industry owing to difficulties associated with the relatively low yield of ferrate(VI), the instability of the chemical depending on its method of preparation, and the lack of adequate studies that have demonstrated its capabilities and advantages over existing water and wastewater treatment methods. Fundamental study is thus required to explore the new preparation methods focusing on increasing the production yield and products stability and avoiding using hypochlorite or chlorine as the oxidant. Also, the application of ferrate(VI) in drinking water treatment has not been studied systematically and future work in this field is recommended.

Removal of Iodinated X-Ray Contrast Media During Drinking Water Treatment

Environmental Context.In recent years, many micro-organic pollutants, e.g. pharmaceuticals and personal care products (PPCP), have been observed to be persisting through wastewater treatment and occurring in the environment. Persistent micropollutants are of particular concern owing to the fact that some of them have been found in drinking water, and iodinated X-ray contrast media (ICM) are one group of such pollutants. Abstract.The present study investigates the removal of five iodinated X-ray contrast media (ICM) during drinking water production from surface water at a full-scale water works, which comprises coagulation/flocculation, intermediate ozonation, in-line filtration and adsorption with activated carbon. The elimination rates over all treatment units for the non-ionic ICM (iomeprol, iopromide, iohexol and iopamidol) were determined to be approximately 70%. In particular, intermediate ozonation can remove 30% on average of the non-ionic ICM, whereas it cannot remove the ionic diatrizoic acid, and the granulated activated carbon filters can achieve a further 50% removal of non-ionic ICM. However, over 100 ng L−1 of ionic diatrizoic acid and 40–100 ng L−1 of non-ionic ICM were found in the produced drinking water.

Factors influencing the mobilisation of polycyclic aromatic hydrocarbons (PAHs) from the coal-tar lining of water mains

Abstract Coal-tar was commonly used as an internal lining for corrosion protection of water pipes from the 19th century. In this project the principal mechanisms leading to the occurrence of Polycyclic Aromatic Hydrocarbons (PAHs) in those water mains were investigated. The results showed that the occurrence of PAHs in a distribution system was linked to the presence of the disinfectants chlorine and chlorine dioxide. In laboratory experiments it was demonstrated that the coal-tar surface represents a substrate for the growth of biofilms which exhibits protective effects. Generally, hostile environmental conditions for microbiological activity of the biofilm such as disinfection, stagnation periods and anaerobic conditions could be identified as important factors which favour the occurrence of PAHs in drinking water. Immediately after stagnation periods an increase of PAH concentrations was observed. Furthermore, it was clearly shown that disturbances in the hydraulic regime such as water hammers, operation of valves and rapid increases in flow velocity can result in enhanced PAH concentrations by the destabilisation of the biofilm matrix or high shear forces affecting the pipe walls resulting in the release of particles highly contaminated with PAHs which may be responsible for the contamination of the drinking water.

The construction of a sand profile sampler: Its use in the study of the Vorticella populations and the general interstitial microfauna of slow sand filters

Abstract A simple and inexpensive method is described by which the component groups of the interstitial fauna can be examined undisturbed by direct microscopy. The method has been developed specifically to locate and enumerate the functional interstitial microfauna of slow sand filters used in water purification and it is designed to demonstrate the spatial relations of the constituent populations as they develop in time in a flowing system. The sampler has been successfully applied to monitoring the development of Protozoa and Rotifera in pilot scale and full scale slow sand filters at the London Metropolitan Water Boards Walton and Ashford Common Treatment Works. Results are presented for the incidence of the general microfauna and for the development, vertical distribution and effect of flow rate on the Vorticella populations.

Evaluation of serratia marcescens bacteriophage as a tracer and a model for virus removal in waste stabilisation ponds

The use of Serratia marcescens bacteriophage as a tracer and a model for virus removal in the Cayman Islands9 waste stabilisation ponds was investigated. A series of bench-scale experiments was designed and carried out to determine the survival of Serratia marcescens bacteriophage in the various stages of a waste stabilisation pond system. The study investigated whether the physico-chemical conditions expected in facultative and maturation ponds precluded the use of phage tracers. By the end of the 6th day, phage in filtered and unfiltered raw sewage and facultative pond samples, in normal sunlight, was undetectable. In the maturation pond samples, in normal sunlight, phage was undetectable by the 4th day. There was a high correlation between increased phage reduction and increased pH levels. The phage was still detectable on day 13 in maturation pond experiments kept in the dark. Therefore the study concluded that Serratia marcescens bacteriophage may be useful as a tracer in ponds with retention times up to 14 days provided average pH at the outlet is

The toxic effects of selected heavy metals on unadapted populations of Vorticella convallaria var similis

Abstract The presence of large amounts of heavy metals in sewages may cause severe disruption of the biological processes involved in sewage treatment, and thus a decline in the quality of the effluent produced. Unadapted populations of Vorticella convallaria var similis, a sessile peritrich protozoan found abundantly in healthy rivers, activated sludge, percolating filters and slow sand filters, were subjected to a range of concentrations of three common pollutant metals. It was found that these populations were killed by concentrations of, and above, 0.0005 mg/l. of the free metal ion of either lead or mercury. Colonies were also killed by concentrations of, and above, 0.075 mg/l. of the free metal ion of zinc. 12 hr 50% lethal doses were calculated, and for V. convallaria var similis were found to be 0.0036 mg/l. for lead, 0.005 mg/l. for mercury and 0.29 mg/l. for zinc.

A pilot rural water surveillance project in Indonesia

Rural water supply in Indonesia is characterized by many hundreds of thousands of public and private unpiped facilities. This article describes cost-effective methods which have been developed for sanitary inspection of these facilities. The results of the pilot surveillance project in Java have been evaluated and are to be used as the basis for remedial action strategies which will be replicated in other provinces of Indonesia.

Microbiological studies on two Oxfam sanitation units operating in Bengali refugee camps

Abstract Microbiological investigations on the efficiency of the Oxfam sanitation system in Bengali refugee camps showed that the combined system of anaerobic digestion and retention is effective in reducing the bacterial and suspended solid content of raw sewage. The efficiency of Vibrio and coliform removal was > 96%; Ascaris numbers were reduced by 97% whereas the efficiency of suspended solid removal was > 91%.

Multi-stage surface water treatment for community water supply in Colombia

Using a multi-barrier treatment for drinking-water greatly increases the potential of slow sand filters. Gerardo Galvis, Jan teun Visscher, and Barry Lloyd describe how this treatment process contributes to a remarkable overall improvement in water quality.

THE RELATIONSHIP BETWEEN WATER-RELATED DISEASE AND WATER QUALITY WITH PARTICULAR REFERENCE TO URBAN WATER SUPPLY IN A DEVELOPING COUNTRY

The problems of urban water supply and water related disease in the P_�ericas are examined in the context of population growth and geographical features. The debate concerning the transmission of potentially water-borne pathogens is discussed. The factors affecting the quality of water supply services in a large metropolitan area (Lima) are described and the epidemiological characteristics of water-related disease sUI!1I!larised and compared with data from Africa (Lesotho). A water quality additive index is proposed in order to identify the level of risk for each metropolitan district. This incorporates the presence of faecal coliforms and the absence of chlorine residual. A water-related disease product index (DPI) is also proposed which incorporates the incidence of typhoid,hepatitis and diarrhoea. The indices were matched for all districts, where adequate data were available, and a strong correlation was noted. The water quality index was divided into categories (A,B,C) and it was observed that these were generally dependent upon the water supply service levels. It is concluded that disinfection control is grossly deficient in most developing countries but essential for the control of water-borne disease.