Pressure sensors for BOD testing and measurements.
OxiTop IS 6, IS 12
Measurement using OxiTop® Biological Oxygen Demand (BOD) Respirometer Systems is based on a pressure measurement in a closed system: microorganisms in the sample consume the oxygen and form CO2. This is absorbed by NaOH, creating a vacuum which can be read directly as a measured value in mg/l BOD.
The sample volume being tested regulates the amount of oxygen available for a complete the respirometer system's BOD measurement. BOD measurement ranges of up to 4,000 mg/l can be measured with the respirometer system using different sample volumes.
The OxiTop® BOD respirometer system's heads (green and yellow for differentiation of inflow/outflow) have an AutoTemp function: if the sample temperature is too cold, the start of BOD measurement is automatically delayed (by at least 1 hour) until a constant temperature has been reached.
Apart from the automatic storage of 5 measured values (1 value per day) by the respirometer systems, further measured BOD values can be read at all times during or after the period of 5 days, which permits the tracking of check values or measurements over longer periods. The OxiTop BOD respirometer system instrumentation measurement system also offers simple operation, improved controllability, and non-toxicity.
OxiTop Control 6, Control 12
The OxiTop® Control Biological Oxygen Demand (BOD) respirometer system is an advanced version of the successful OxiTop® BOD respirometer system that uses software-controled functions and an infrared interface to communicate with a handy controller, the OC 100. These respirometer systems enable the simultaneous and grouped start, management, storage and tracking of 100 BOD measuring heads via the controller and allows them to be tracked on a large display with graphic evaluation. BOD measurement data from the respirometer systems can be transferred to the PC for evaluation and documentation via the AK-540/B cable (order no. 902842) and the communication program Achat OC (order no. 208990).
The respirometer system's biological oxygen demand (BOD) data can be called up at any time, even during sampling, thus enabling checking of the samples for errors. The respirometer system's display of the progress curve allows immediate detection of irregularities and interferences, such as having the BOD value set too high for the volume used or undesired nitrification. BOD measurement corrections to the respirometer systems can thus be made at an early stage. The OxiTop® Control BOD respirometer systems offer you simple operation, improved controllability, non-toxicity, and measuring ranges of up to 4,000 mg/l BOD.
Biological Oxygen Demand Measurements according to EN 1899-1 and EN 1899-2 and for self-checks
Biological oxygen demand (BOD) determination is still one of the most important parameters in water resource management. BOD measurements can be used to evaluate the impact of biodegradable substances in waters and wastewater by measureing the quality of water and treatment results in wastewater. In addition, BOD instrumentation measurments are used in the planning and design of wastewater treatment facilities. The OxiTop® BOD respirometer systems offer a unique, modular and mercury-free way to make BOD measurements. The respirometer systems are not only suitable for BOD determination, but also for measuring biodegradability and depletion.
In routine use, BOD determination is used to check the wastewater in the inflow and discharge of wastewater treatment plants. Depending on the measurement site and type of wastewater the BOD value can lie between a few mg/l and several thousand mg/l. Several BOD testing methods are available for carrying out the measurement.
Various systems for BOD determination methods
In "dilution BOD" the oxygen content of a sample is measured with an oxygen sensor before and after an incubation period of 5 days. The difference between the measurements is the BOD5 value; this is the official EPA BOD measurement method. The Oxi 1970i Portable Dissolved Oxygen Meters can be used for dilution BOD measurments.
In "BOD self-checks" with the respirometer system the reduction in oxygen causes a definite pressure difference which can be measured by a pressure sensor. This BOD measurement method is very easy and practical to carry out.
Although both methods are very different, the respirometer system BOD measurements correlate for discharge analysis in municipal wastewater treatment facilities. Both BOD measurement methods require that the samples to be kept at 68 °F (20 °C) for 5 days. WTW offers a temperature controlled box for use with Oxitop® BOD respirometer systems.