Wastewater treatment optimisation provides cost savings

The HACH LANGE optimisation system combines process measurement technology with advanced RTC control modules to provide substantial savings in operational costs, whilst maintaining compliance with consent values.

In combination with HACH LANGE sensors, Nutrient Removal and Sludge Treatment Processes can now be easily optimised in order to achieve savings in aeration energy and chemical consumption, even on small waste water treatment facilities.

Sensor technology

In recent years, improvements in sensor technology have focused on greater resolution and accuracy in combination with longer intervals between calibration or service. However, in order for an RTC system to operate effectively it is also necessary for sensors and analysers to be able to provide information on the quality of the signal and the service status.

RTC opportunities

Stand-alone wastewater treatment optimisation solutions (WTOS) control modules are now available to optimise individual treatment processes at treatment plants. These can be easily integrated into an existing plant structure and currently include (1) the chemical elimination of phosphorus and (2) dissolved oxygen adjustment according to the actual NH4-N load in an aeration tank. Control modules for sludge management as sludge retention time controller or desludging controller will be added in the near future.

In addition to the stand-alone modules mentioned above, it is also possible to combine different RTC modules to optimise an entire plant.

Stand-alone RTC example: chemical Phosphate removal

The measurement technology for phosphate has advanced considerably in recent years in tandem with a reduction in capital and operational costs. As a result, an easy to integrate RTC module in the phosphate removal process can deliver pay back periods of less than one year.

The measurement of phosphate levels in combination with an RTC system can be utilised to manage the dosing of precipitant salts.

Wastewater treatment plants operating an open loop real time control system for phosphate removal have demonstrated considerable savings – a UK works has saved approximately 37% of the ferric sulphate cost and 57% of caustic chemical costs and a plant in Italy has shown 50% cost savings in comparison with a constant dosing system, which represents a 7 month payback.
If closed loop control is applied, the RTC system requires a measurement of phosphate levels immediately after dosing. As a result, the Phosphate concentration can be held at a fixed desired level and the control performance is monitored.

The UK project demonstrated that the RTC system was able to respond quickly to ammonium influent spikes and to maintain a stable effluent ammonium level. The trial also demonstrated that the RTC system was able to reduce methanol consumption by 50% and energy (measured as air flow) by 20%. The system has now operated successfully for more than one year.

Summary

Recent advances in sensors, analysers and controllers mean that wastewater treatment no longer has to be managed on a ’worst case scenario’ basis. Processes can now be monitored and adjusted instantaneously to maximise efficiency and improve process stability. Cost reduction is obviously a key benefit, but the ability to reduce energy consumption is becoming an important objective.

For more information contact info@hach-lange.co.uk.