In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water.
The chemical oxygen demand can be measured using different methods, direct or indirect. Regularly the COD value is determined by means of samples that are analysed using laboratory test methods. These off-line methods can be time consuming while the COD value is an essential parameter in the biological treatment process.
Fortunately, there are some alternatives available to laboratory test methods, for example automated COD analyser systems. These on-line instruments are used in a sample stream of the wastewater process and are automatically providing a number of measurements in a period of time. Compared to off-line measurement this method is much quicker providing an easier way to analyse the chemical oxygen demand. However, on-line analysers are normally used in a bypass of the process stream which makes this an indirect measuring method.
Off-line, at-line, on-line or in-line measurement?
The quickest method for COD measurement is through the use of in-line process equipment such as the Model 9585 COD meter of Rhosonics. The sensor of this instrument is placed directly into the process stream, which means that the chemical oxygen demand can be monitored continuously, directly and real-time. The COD value is displayed at the instrument without any time delay and can be used for process control purposes, improving the efficiency of the biological treatment process. Additionally this product can be used as an early warning system in case of unexpected process changes.
Continuous COD monitoring to guarantee a high standard in brewery wastewater treatment
Wastewater treatment plants (WWTP’s) of breweries choose in-line COD measurement to protect their treatment facility against high COD peaks. This measuring method helps to reduce the overall operating costs and makes it easier to comply with conditions for discharge consent. Upset process conditions – resulting in the destruction of the biological process – are prevented and unintended spillage of raw material can be detected immediately.
Beer is 95% water, which makes it a critical resource for breweries. Beer giants like Heineken are focusing on water efficiency and are working on reducing their impact on the increasing global demand for water. Investments in brewery wastewater treatment are contributing to this goal and in-line COD instruments, like the Model 9585 COD meter, are used to ensure the high standard of wastewater treatment. Due to the policy of Heineken, Rhosonics became the preferred supplier for in-line COD instruments. The Model 9585 COD meter is used by WTTP’s of Heineken breweries all over the world.
The Model 9585 COD meter
Wastewater treatment plants are using the Model 9585 COD meter of Rhosonics in a pipe line, reservoir or launder to optimise and protect their biological purification process. All applications of this model are found in the influent stream of the treatment facility. The COD value is continuously available (on the screen of the analyser) and is not affected by the hardness, the presence of detergents like caustic nor suspended solids. Besides COD, the suspended solids load of the water can also be monitored as additional process parameter.
The COD measurement of the Model 9585 is based on the hybrid ultrasonic / conductivity technology of which sound velocity is the most important measurement. The factory calibration is based on the ultrasonic properties of a variety of most common organic materials, such as alcohols and sugars. These properties are not affected by vibration, transparency or viscosity.