Bulletin Number Two 1984

pollution. Hong Kong has a lot of solid wastes, some of which could be made use of in the mushroom industry. Before 1969, local mushroom growers could supply only about 7% of the total local consumption o f the straw mushroom. The rest were imported from Thailand, Taiwan and Mainland China. In 1971, cotton wastes were first used to grow strawmushroom, and by 1982, local production of the mushroom has reached 74% of the total local consumption. Recently we have developed a new synthetic log consisting of sawdust and used tea leaves to grow Lentinus mush room. It is estimated that production of sawdust and used tea leaves in Hong Kong is about 60 tonnes and 64 tonnes respectively every day. Hong Kong also produces about 400 thousand tonnes of cracked wood from the building industry and about 10 thou sand tonnes of horse manure from the Royal Hong Kong Jockey Club every year. These solid wastes could be used to grow different kinds of edible mushrooms. K .Y . Chan: My own research interest is on the recycling of liquid effluent, particularly domestic sewage effluent in Hong Kong, with the final goal o f turning the potential pollutants in the sewage effluent to edible single cell protein on the one hand, and purify the effluent for possible reuse on the other. We can make use of the inorganic nutrients in the treated sewage effluent in a well controlled system to produce low-cost single cell algal protein for mari culture and livestock feed. The idea involves the selection and cultivation of some unicellular algal species rich in protein content in the treated sewage effluent, so that food protein can be produced and at the same time the levels of inorganic phosphates, ammonium and nitrates can be greatly reduced from the effluent, which can then be considered as 'chemically and biologically clean' for direct discharge into the marine environment. The algal protein can then be provided for mariculture utilization. Today we have been able to select one algal species which can serve the dual purpose of waste water purification and waste recycling through the production o f algal protein from sewage effluent. This is an unicellular green alga, Chlorella, which has a protein content of 51% (dry weight). With a retention of eight days in treated sewage effluent, the cells can remove up to 98%of phosphate, 86-100% ammonium and 98% of nitrates from the sewage effluent. Replacement of up to 30% of the fish meal by the dried algal cells as fish feed has been quite successful in the cultivation of silver carp. A t present, we are searching for other possible algal species which have even higher protein content for research purpose. On the other hand, we are also screening algal species for those that can absorb the heavy metal 'cadmium' for possible removal of cadmium from sewage effluent containing high levels of this metal. M .H. Wong: My research interests include pollution ecology, bioassay of pollutants and recycling of waste materials (animal manure, sewage sludge, refuse compost and food processing wastes). We have involved in an ecological survey of Gin Drinkers' Bay landfill to study the effects of methane and leachate on soil characteristics and plant growth, for a period of two years. Apart from chemical analysis, bioassay of pollutants can provide additional information on their effects on the aquatic biota for the protection of the aquatic environment. Recycling of waste materials does not only mitigate part of the pollution problem but also reutilizes the inherently rich plant nutrients (i.e. nitrogen and phosphorus). Research projects have been conducted using these wastes for algal growth, agricultural application (as soil conditioner/fertilizer), supplementary feeds for freshwater fish, and biogas production. Experiments related to composting of pig manure under different environmental conditions are being carried out in order to turn it into a more valuable product. H o w is the level o f p o llu tio n measured? O.W. Lau: In measuring the level of pollution, we should pay special attention to the following: (1) the sample has to be a representative one; (2) sample analysis has to be carried out by trained personnel; (3) proper procedures have to be followed to determine the degree of contamination and account has to be taken