Maximising biogas in anaerobic digestion by using engine waste heat for thermal hydrolysis pre-treatment of sludge.

Dublin's Ringsend WWTP was designed to serve a population of approximately 1.2 million p.e. with a sludge production of 37,000 dry tonnes per year after upgrading to full secondary treatment. Several technical solutions were put forward as part of a design, build, finance and operate (DBFO) competition, with the chosen solution being a proposal by Black and Veatch for a combination of sequencing batch reactor (SBR) technology and anaerobic digestion with Cambi thermal hydrolysis pre-treatment (THP). The THP plant was built by Cambi and handed over to B&V in 2002. The plant is now operated by Celtic Anglian Water. In September 2004 a test was carried out on the mass and energy balance of the plant following 2 years of operation and is detailed in this paper. The process enables digestion at very high dry solids feed and low hydraulic retention time. The plant was built with three digesters of 4250 m3 each and is fed with hydrolysed sludge at 11% DS. There are four no. 1 MW Jenbacher engines operating mainly on biogas. Each pair of engines is fitted with a waste heat boiler with a capacity of one tonne steam per hour. These boilers have sufficient capacity to provide 80% of the steam required for the THP, which in turn provides all the heat for the subsequent digestion in the form of hydrolysed feed. There are two main biogas boilers for top up steam and other uses of the biogas including thermal oxidation of concentrated odours.

A survey of literature relating to administrative dietetics.

This article provides insight into the complexity of hospital foodservice operations by reviewing selected published material and identifies subject areas that are well developed in the literature. A survey was made of leading professional journals, and an annotated bibliography was compiled of pertinent articles from the Journal of American Dietetic Association from 1965 to 1982. Also, the research abstracts published annually by the Society for the Advancement of Foodservice Research were consolidated for the period 1971-1982. Analysis of over 500 professional articles and research abstracts indicated that personnel management was the most studied area, followed by financial management, productivity, and computer use. Topics which seemed to be overlooked included unionization, cafeteria policies, and allocation of production labour cost.