CO129-627-2 Fertilizer factory new territories- contains drawings 1-12-1950 - 31-1-1952 — Page 87

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Nevertheless, the nightsoil which I have seen in bulk appears to be of a pumpable consistency but I can find no verification of this condition in the form of records of determinations of the water content of the nightsoil, which may vary appreciably from batch to batch. On an assumption of a moisture content of 80% the liquid in 180 tons would be 144 tons.

3. Refuse. The analysis of the refuse, which is reproduced in section

B.8 of this report, indicates that at least 550 tons of material suitable for making compost should be recoverable from the refuse every day.

4.

For the quickest development of fermentation in compost and for the most rapid and uniform decomposition of the material, experience in other countries has shown that under their conditions the most favourable moisture content is in the neighbourhood of 60% to 65% by weight. There is no information about the moisture content of the urban refuse but if the compostable garbage from it be assumed to have an initial moisture content of 45%, the additional liquid required to raise the degree of moisture to 60% of the total weight would be ton per ton of the compostable material in its initial condition. The 550 tons of garbage would therefore require 206 tons of liquid. The initial moisture content of the garbage may be higher than 45% in the wet season, but, if the same quantity of garbage has its moisture content increased by rain to 549, it will still absorb another 206 tons of liquid without reaching a moisture level above 65%%.

I estimate, therefore, from the information at present available, that the normal minimum requirements of liquid for establishing and maintaining the best conditions for biochemical activity in the compost will be 200 tons per day. It appears from the estimates in section C.2 that this quantity of liquid may not be available in the raw nightsoil. However, it is probable that the balance of the requirement might be supplied by foul water from the washing of nightsoil containers, but alternative sources would be a river running ncar the Tsun Wan site and rainwater stored in tanks. Liquid draining from the compost would also be retained for re-use.

The_consequences of water carriage sanitation. The probability is that use of the water carriage system of sanitation in the urban arca will gradually extend and, correspondingly, the quantity of nightsoil will decrease.

Under proper conditions of moisture and acration, organic garbage will ferment by itself and decorpose into a humic material, but tho agricultural value of the product is naturally less in the absence of nightsoil or sewage sludge from the ingredients. particular, owing to the lack of nitrogenous matter in its composition, the product will have a high Carbon/Nitrogen ratio.

In

However, as the quantity of nightsoil decreases, provided that the moisture requirement for optimum biochemical activity was made up from other sources, the treatment of the garbage by the composting method would be able to continue and the main installation, comprising handling and sorting plant for the refuse, pulverizers and conveyors for the compostable garbage, fermentation compartments, compost transfer equipment and liquid distribution pipework, would continuc in operation.

Eventual complete supersession of the pail system by water carriage sanitation would mean that such arrangements as had been provided for the emptying and cleansing of nightsoil pails would, together with the pails themselves, no longer be required. The nightsoil barges might be put to use for conveying screen washings or sewage sludge from the