Cairo Sludge Disposal Study

This paper describes the establishment of the Cairo sludge disposal study which is being funded within the Mediterranean Environmental Technical Assistance Programme through the European Investment Bank and promoted by the Cairo Wastewater Organization. The study is a demonstration programme to show how the problems of sludge disposal from large, rapidly developing cities, such as Cairo, can be solved through the establishment of a practical system for the safe re-use of sewage sludge in agriculture. It is being carried out principally through a series of demonstration field trials and the development of ettensive information. This study is of relevance to Egypt and other countries with similar agricultural and environmental conditions, where (a) sludge production is increasing, (b) water protection is essential, and (c) appropriate environmentally acceptable solutions are urgently required.     

Assessment of the Fate of Selected Adsorptive Pesticides at ADAS Rosemaund

Data are presented on four pesticides applied to agricultural land at the Agricultural Development Advisory Service, Rosemaund, in the west of England. The farm covers a well-defined and isolated water basin of cracking heavy clay loam soils drained by a single stream. Levels of the relatively particle-bound pesticides trifluralin, deltamethrin, chlorpyrifos and fenpropimorph were measured in drainage water and field soils following application. Observed concentrations in water were generally below 1 μg/l with occasional peak levels exceeding 10 μg/l during storm rainfall events. Unexpectedly high peak levels of deltamethrin of around 2 μg/l highlighted significant bypass flow mechanisms from the surface soils during the autumn. Additional bioassay experiments showed that levels of chlorpyrifos, lethal to Gammarus pulex , reached the stream during spring 1993. The Rosemaund farm has been the site of a continuing investigation into the movement of agricultural pesticides to surface waters since 1987, and this report represents the final work conducted in the autumn of 1992 and spring 1993.     

Public Perception of River-Corridor Management

Research into the public's perception of water and river-corridor quality has been undertaken to assess the importance of these aspects to the public's selection of sites for use in recreation.
Preliminary results from two on-site questionnaire surveys involving a number of river user groups suggested that:

• i. 

  Whilst there was a strong association between perceived water quality and the presence/absence of individual water-quality variables, the presence of indicators of 'good'water quality were less likely to influence perceived water quality than the presence of indicators of 'bad'water quality;
• ii. 

  There was an overwhelming desire for trees and a strong preference for vegetational diversity within the public's perceived ideal river corridor setting; and
• iii. 

  An equally strong preference for mature, sinuous rivers with natural channels and banks.

These results suggest that there is a close relationship between the type of riverscape preferred by the public in their use of rivers for recreation and amenity, and that desired by conservationists.     

Cryptosporidium and Water: A Review

Infection with the protozoan parasite Cryptosporidium parvum is now recognized to cause acute self-limiting gastroenteritis in immunocompetent human beings, and in certain groups of immunocompromised individuals symptoms can persist indefinitely. There is no effective specific drug treatment for cryptosporidiosis. Transmission of Cryptosporidium sp. oocysts via the waterborne route has received attention recently because of the outbreaks which have occurred both in the US and the UK, affecting large numbers of people. This paper reviews the disease in humans, the significance of the waterborne route of infection, and identifies gaps in our current knowledge which the National Cryptosporidium Research Programme attempts to address.     

Plumbosolvency Effects and Control in Hard Waters

A laboratory lead-pipe rig has been used to support Anglian Water's successful orthophosphate dosing programme to reduce plumbosolvency. The hard waters in the region generally fall into low or high plumbosolvency categories according to the types of crystalline deposit formed. To improve the cost-effectiveness of plumbosolvency control, the effects of temperature, phosphate doses, blending and alternation of these waters were investigated.
Initial phosphate concentrations must be above 0.6 mg P/l (as phosphorus) to establish plumbosolvency control. Subsequently, phosphate doses may be reduced, provided that dosing is continuous and sufficient phosphate reaches the extremities of the distribution system. When high and low plumbosolvency waters are blended before distribution, both (or the mixture) must be phosphate dosed. However, where waters alternate in distribution, laboratory studies have shown that low plumbosolvency deposits are more stable, resulting in low lead concentrations. The high plumbsolvency of some hard waters may be due to the presence of low concentrations of humic substances.