Owing to the launched refurbishment of the digestion tanks in the Central Waste Water Treatment Plant (ÚČOV) in Prague, the administrator of water management infrastructure, PVS a.s., has decided to order an expert opinion that would calculate and compare the energy consumption of the tanks that have not yet undergone renovation and those that already have.

For this purpose, thorough measurement of the pivotal values (especially the temperatures and fl ows of septic sludge and heating water) was carried out in order to determine the quantity of heat consumed by the plant’s sludge management, or, more precisely to maintain the temperature of the sludge in the tanks at the required level. The results of the measurement and the model calculation have confi rmed that the share of thermal losses through transmission in the total heat consumption is very small, currently amounting to 15–20 %,
and after the reconstruction less than 10–15%.
Th is fact is absolutely essential since it proves that the digested sludge leaving the anaerobic stabilisation procedure conceals a great heat potential that
could be re-utilised.

Th e realistic solution appears to be implementing heat recovery by means of simple recuperation through a suitable sludge-(water)-sludge exchanger, owing to which it would be possible to save even more than 50 % of the current heat requirements of the water treatment plant’s sludge management. In annual terms, it concerns more than 20,000 MWh of heat (over 70 thousand GJ), which could be supplied to, for example, the central community heating distribution network of the nearby Juliska Heating Plant. The precondition is the construction of a connecting heating water conduit whose payback period, with regard to the minimal operating costs, would be very short (several years). Therefore, it was recommended to confi rm this solution’s feasibility by means of a detailed study.

Tomáš Voříšek
Email: tomas.vorisek@svn.cz
Tel.: +420 224 252 115

The article is from News at SEVEn number 2/2010, which is available to download here.

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