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The effect of sand filter media thickness on the performance of faecal sludge (FS) drying beds was determined in terms of: dewatering time, contaminant load removal efficiency, solids generation rate, nutrient content and helminth eggs viability in the dried sludge. A mixture of ventilated improved pit latrine sludge and septage in the ratio 1:2 was dewatered using three pilot-scale sludge drying beds with sand media thicknesses of 150, 250 and 350 mm. Five dewatering cycles were conducted and monitored for each drying bed. Although the 150 mm filter had the shortest average dewatering time of 3.65 days followed by 250 mm and 350 mm filters with 3.83 and 4.02 days, respectively, there was no significant difference (p > 0.05) attributable to filter media thickness configurations. However, there was a significant difference for the percolate contaminant loads in the removal and recovery efficiency of suspended solids, total solids, total volatile solids, nitrogen species, total phosphorus, chemical oxygen demand, dissolved chemical oxygen demand and biochemical oxygen demand, with the highest removal efficiency for each parameter achieved by the 350 mm filter. There were also significant differences in the nutrient content (NPK) and helminth eggs viability of the solids generated by the tested filters. Filtering media configurations similar to 350 mm have the greatest potential for optimising nutrient recovery from FS.

In order to determine the potential indicator value of protozoa and metazoa for control of sequencing batch reactors, mixed liquor solids were examined microscopically for 200 complete cycles from start-up; a total of 100 days. Over the first 40 cycles a healthy, diverse, protozoal population was established which comprised free-swimming, crawling and attached ciliates. During this period the reactor demonstrated efficient removal of COD and suspended solids but did not nitrifiy. With the onset of complete nitrification there was a drastic change in microfauna which became dominated by flagellated protozoa. At around the 80th cycle rotifers appeared and at cycle 100 attached ciliates became the dominant group. The protozoal composition of the mixed liquor responded to reactor shocks such as pH variations and was shown to be a good indicator of the nitrification efficiency of the reactor.

From the middle ages until the early part of the nineteenth century the streets of European cities were foul with excrement and filth to the extent that aristocrats often held a clove-studded orange to their nostrils in order to tolerate the atmosphere. The introduction in about 1800 of water-carriage systems of sewage disposal merely transferred the filth from the streets to the rivers. The problem was intensified in Britain by the coming of the Industrial Revolution and establishment of factories on the banks of the rivers where water was freely available for power, process manufacturing and the disposal of effluents. As a consequence the quality of most rivers deteriorated to the extent that they were unable to support fish life and in many cases were little more than open sewers. This was followed by a period of slow recovery, such that today most of these rivers have been cleaned with many having good fish stocks and some even supporting salmon. This recovery has not been easy nor has it been cheap. It has been based on the application of good engineering supported by the passing and enforcement of necessary legislation and the development of suitable institutional capacity to finance, design, construct, maintain and operate the required sewerage and sewage treatment systems. Such institutional and technical systems not only include the disposal of domestic sewage but also provisions for the treatment and disposal of industrial wastewaters and for the integrated management of river systems. Over the years a number of institutional arrangements and models have been tried, some successful other less so. Although there is no universally applicable approach to improving the aquatic environment, many of the experiences encountered by the so-called developed world can be learned by developing nations currently attempting to rectify their own aquatic pollution problems. Some of these lessons have already been discussed by the authors including some dangers of copying standards from the developed world. The objective of this paper is to trace the steps taken over many years in the UK to develop methods and systems to protect and preserve the aquatic environment and from the lessons learned to highlight what is considered to be an appropriate and sustainable approach for industrialising nations. Such an approach involves setting of realistic and attainable standards, providing appropriate and affordable treatment to meet these standards, establishment of the necessary regulatory framework to ensure enforcement of the standards and provision of the necessary financial capabilities to guarantee successful and continued operation of treatment facilities.