25 August 2005 -- Throughout the food and beverage industries, there is a constant requirement to monitor and control wastewater and effluent before discharge from the plant in order to comply with consent levels. In addition to this, process plants must also recognise that unless close control is exercised over all stages of waste treatment, the treatment procedure itself can become ineffective. Monitoring suspended solids and turbidity in dairies and dairy production plants is a key parameter for assessing the quality of the effluent in respect of meeting consent levels.
The results can also be used as an aid for minimising waste, as well as indicate if there is any significant product loss through operator error.
'Within the dairy industry, biological treatment plants are at constant risk from spillages and these must be dealt with promptly before excessive quantities of milk and waste liquid from milk products can find their way into the biological treatment plant,' comments Angus Fosten of Partech Instruments.
'The problem is that dairy product residues can contain relatively high levels of BOD and these can upset the delicate balance of the biological treatment plant.
Re-establishing the correct balance in the treatment plant can be expensive and lengthy, resulting in plant downtime and loss of production'.
Employing continuous turbidity monitors within the treatment plant provides a reliable and effective approach to identifying when a problem has occurred, allowing plant operatives to take remedial action.
It also has the added benefit of indicating the performance of the treatment plant by measuring the presence of undissolved solids prior to discharge.
'Turbidity is now widely used within the food and drink industries on both final effluent and crude effluent,' reports Nigel Stevens of consultants McDonald Stevens Associates.
'On the crude effluent a turbidity monitoring systems can provide a reliable method of on-line measurement to alarm or divert high strength wastewaters into a separate tank'.
The inclusion of a divert tank allows plant managers to decide whether to take the option of tankering the waste off-site or returning it into the main treatment stream.
Partech Instruments has a long history of providing solutions for determining turbidity and levels of suspended solids in effluent treatment plants within the dairy industry.
A well used and proven approach involves the installation of its Turbi-Tech 2000 Sensor and 7200 Monitor, which together provide operatives with a constant indicator of the levels of suspended solids and turbidity at given points with the treatment process.
Available in two versions, the LS and LA, the Partech Turbi-Tech 2000 sensor uses Infrared 90degree light scatter as its measuring principle.
The LS version is designed to monitor low levels of solids or turbidity and is typically installed at the final effluent discharge point.
The Turbi-Tech LA has an operating range suitable for use in aeration systems and may be used to monitor mixed liquor suspended solids and returned activated sludge.
Both versions of the Turbi-Tech 2000 feature a self-cleaning system, which means that the optical surfaces of the sensor cannot be contaminated and performance adversely affected.
'The self-cleaning capability is essential for dairy plants,' says Angus Fosten, 'as there are always a high proportion of fatty milk materials contained within manufacturing residues.
Apart from enhancing the instrument performance, it means that maintenance is minimised resulting in low ownership costs'.
The 7200 Monitor combines with all the Partech Instruments infrared sensors to give a cost-effective solution to suspended solids measurement applications.
It is designed for both internal and external locations (IP65 rating), and features a large character display of the measured value combined with a scrolling information bar showing output status.
The monitor also provides an analogue output and contains two relays that can be configured as high, low or fault alarms.
Configuring, calibrating and interrogating the 7200 Monitor is made simple through the use of set up wizards.
The calibration routine makes full use of the calibration cells that are available for all Partech sensors, thereby reducing the need for laboratory tests and providing enhanced confidence in the validity of the reading.
Full password protection ensures that the system is secure from interference and cannot be altered in error.
'Employing turbidity monitoring systems that operate 24/7 means that plant operatives are able to watch over the performance of the treatment process and be warned of any problem immediately it occurs,' says Angus Fosten: 'Breaching discharge consent levels can be very expensive in terms of fines levied.
Equally as expensive can be accidental discharge of products into the effluent treatment process.
By measuring turbidity, plant management can achieve savings in terms of reducing product wastage and ensure that consent levels are not inadvertently breached.
