Wastewater treatment down-time 'not acceptable'

Shasun Pharma Solutions provides research and contract manufacture services to the pharmaceutical industry, including small scale manufacture for clinical trials and full scale commercial manufacture of advanced intermediates and active pharmaceutical ingredients. With both large and small customers spread across Europe, North America, Latin America and Asia, the business has to be able to demonstrate a high level of environmental management.

Craig Goodman manages Shasun's wastewater treatment plant which employs three 2,500m3 tanks to treat industrial wastewater by an activated sludge process that utilises oxygen and a biological floc to break down the waste materials. Craig says he uses liquid oxygen rather than mechanical aeration because pure oxygen enables the plant to respond much more quickly and requires around one fifth of the volume for aeration.

The liquid oxygen is stored onsite and provides Craig with almost instantaneous control of dissolved oxygen in the plant. He says: This is made possible as a result of the new breed of dissolved oxygen sensors that we use – the 'LDO'.

In the past, we relied on traditional membrane based DO sensors but these required a high level of maintenance and tended to drift; it was usually necessary to recalibrate every week. However, the new LDO sensors last for over a year without recalibration and we then simply replace the sensor cap, so our monitoring activity is now significantly easier and more accurate and reliable.

The liquid oxygen is vapourised and fed into the tanks via a single entry point Venturi at around 7bar and the objective is to maintain DO at 3mg/l +/- 0.2. In addition to online sensors for pH and ammonium, the LDO sensors are connected to an SC1000 controller which also monitors the 'health' of the sensors and interfaces with the plant's control systems.

Emphasising the importance of accurate DO control, Craig says: In addition to the waste stream from our own plant, we also treat waste from third parties so we do not always know what is coming down the line and that is why we need to be able to respond quickly; overdosing oxygen would kill the bugs and underdosing may cause other problems such as bulking.

Shasun's wastewater treatment facility effectively removes 95% of COD (Chemical Oxygen Demand) which is a common method for the determination of organic pollution. COD testing is therefore conducted onsite and Craig's team employ a HACH LANGE spectrophotometer for this purpose. The pre-filled, bar-coded HACH LANGE COD tubes ensure that every test is conducted in exactly the same way, with exactly the same reagents. Bar-coding ensures that the spectrophotometer recognises each sample and ensures traceability of results.

Craig's team conducts between 30 and 100 COD tests every week and this data helps in the efficient running of the plant and helps ensure compliance with the discharge consent. It also provides Craig with useful information for the calculation of waste treatment charges for third parties. This is because 1 tonne of COD requires approximately one tonne of liquid oxygen for treatment, he explains.
In recent years, all of the laboratory, portable and online wastewater testing equipment has been supplied by HACH LANGE. Craig says: Down-time in our wastewater treatment plant would not be acceptable, so we have to use the most robust and reliable instruments available and in our experience that means choosing HACH LANGE.