The Amtox analyser, when installed at the sewage works inlet, can predict nitrification inhibition well in advance of the toxic load reaching the activated sludge basin. Sewage can then be diverted to storm tanks until the toxic flow has ended. Toxic shock loading can result in the failure of activated sludge and the need to reseed the biological process.

The system works by monitoring the conversion of ammonia and warns of acute and chronic toxicity. Nitrifying bacteria have been immobilised into a PVA porous matrix which is placed into a temperature controlled reactor, allowing rates of ammonia removal to be continuously monitored. The system can therefore prevent the breach of an ammonia discharge consent.

Organic load is also an important measurement for sewage works receiving industrialised waste. PPM’s Protoc system provides real time analysis of dissolved organic carbon (DOC) with a readout in under 3min. The CTOX system uses a TOC analyser to measure before and after a biological reactor to indicate the performance of carbonaceous bacteria used for BOD removal.

PPM’s German counterpart WTW has also recognised the benefit of monitoring the activated sludge process to give an early warning of treatment failure. Increased aeration can then be used to help alleviate the problem. WTW has developed a range of nutrient analysers (Trescon) with separate modules for ammonia, nitrate, nitrite and phosphate. Features such as automatic chemical cleaning, operational diagnostics and PID control outputs are fitted as standard.

All of the instruments described display and create analogue signals suitable for telemetry connection.

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