In situ use of the ammonia process buoy directly within mixed liquors
Recent trials at a large water company’s site have now proven the viability of making “In-tank” Ammonia measurements on a sequencing batch reactor treating anaerobically digested sludge centrate.
This has been made possible by the development of a measuring system, manufactured by Isco-Stip and distributed by Envitech Ltd. The sensor sits in the liquor to be measured and is supported by a stainless steel float, thereby maintaining the same depth of immersion irrespective of the position in the fill and draw cycle.
The primary sensor is a well-proven gas-sensing electrode. However liquor pre-treatment occurs in the wet end assembly removing the necessity for any ancillary equipment. Calibration utilises a standard addition technique and hence only requires one standard. The
measuring chamber is kept clean by back flush with caustic solution after each measurement and there is no need for thermostatic control since measurement and calibration are done at the same temperature, dictated by the bulk liquid.
Initial results show that,
(a) the results are in agreement with other methods,
(b) Nitrification failure is rapidly detected allowing remedial action to be taken before discharge of effluent,
(c) the plant could treat at least twice the load if Ammonia measurement was used to control the aeration period, and
(d) energy could be saved if treatment time was controlled by Ammonia levels rather than on a time base.
The overall monitoring system costs are kept to a minimum since no expensive housing, concrete base, pumps or liquor pre-treatment is required. The comparative capital cost is approximately half that of a conventional system and the operational maintenance costs are also half that of other systems.
Exactly the same system may be employed in conventional plug flow ASP’s or oxidation ditches. The Ammonia signal may then be utilised to control the time of aeration to meet the ammonia load, either by switching blowers off or controlling aerobic/anoxic pocket distribution.
The payback period for the monitoring system when used on medium to large nitrifying plants is estimated to be approximately 1 year.
For further info contact Aquamatic
Unit 20, Lambourne Crescent,
Cardiff Business Park
Cardiff, CF14 5GF
Telephone: 029 2033 7134
Fax: 029 2033 7137
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