Direct and Accurate BOD, 1-28 days measurements, Mercury-free
 

Applications

          Waste Water, Determination of Biological Activity, Waste Water Treatment plants, Analytical Laboratories, Research Centers, Universities

Highlights

• Direct sample selection
• Accurate and direct display of BOD values in mg/l
• User-friendly handling
• User-selectable measuring period from 1 to 28 days (BOD5, BOD7, OECD…)
• Automatic storage of BOD values
• Measuring ranges from 0-40 mg/l to 0-4000 mg/l BOD / sample volume related
• Automatic start function following temperature equalisation of the samples
• Mercury-free, environmentally-friendly BOD determination
• Inductive stirring system with automatic re-centering of stirring rods
• Interface RS 232

References

• APHA, AWWA, WEF Standard Methods 5210 D
• H55 as a supplement to EN 1899-2

Description

          Respirometric methods provide direct measurement of the oxygen consumed by microorganisms from an air or oxygen-enriched environment in a closed vessel under conditions of constant temperature and agitation. Carbon dioxide produced metabolically by the bacteria is chemically bound by the potassium hydroxide solution contained in the seal cup in the bottle.

          The result is a pressure drop in the system, which is directly proportional to the BOD value and is measured by the Lovibond BOD sensor. The BOD level is then displayed directly in mg/l. The BOD values are stored in the sensor memory and can be called up on the large-format display at any time without the need for time-consuming conversion using factors. This means that test series that end on a Sunday can be evaluated during the following week without any problem.

          The measurement period is user-selectable between 1 and 28 days to suit the application. While short measurement periods are useful for scientific applications, standard BOD measurements typically extend over a period of 5 days – and manometric determination of OECD, for example, generally takes place over a period of 28 days.

Measuring ranges and sample volumes

          The BOD level of a sample depends on the quantity of organic matter present, which can vary considerably. The Lovibond BOD measuring system OxiDirect is therefore calibrated for the various sample volumes and the corresponding measuring ranges listed in the table below. The overall measuring range of the system is 0 – 4000 mg/l. For all measuring ranges, BOD is shown directly in mg/l.

Evaluation of measurements

          If the measuring period is set at 24 hours, the Lovibond OxiDirect BOD measuring system records a measurement once every hour. With a measuring period of 48 hours, the unit measures and stores a BOD value once every 2 hours. If the measuring period is between 3 and 28 days, one value is measured and stored each day.

          Current values and stored values may be called up at any time. The table/graph below illustrates an example of BOD5 evaluation. The development of BOD over a period of 5 days is easily seen.

OxiDirect BOD measuring system

          In addition to the BOD unit for measurement and storage of BOD levels, the Lovibond OxiDirect BOD measuring system includes sample bottles, measuring sensors, non-wearing inductive stirring system, overflow measuring flasks for metering of sample volumes, nitrification inhibitor and potassium hydroxide as an absorbent.

Inductive stirring system

          The microprocessor-controlled Lovibond inductive stirring system is non-wearing and maintenance-free. In other words, there are no moving parts in the system.

At regular intervals, the magnetic stirring rods are accelerated and slowed down again, taking them up to maximum speed and back down again. This ensures the centralization of the stirring rods. Stirring rods that move away from the centre of the bottle are re-centered quickly and reliably.
The inductive actuation system guarantees maintenance-free operation (no need to replace drive belts or burnt-out drive motors) for many years.          Delivery Content: OxiDirect, complete unit with 6 sensor heads and control unit with batteries, Inductive stirring unit with power supply, 6 sample bottles, 6 rubber gaskets, 6 magnetic stirring rods, 1 overflow flask, 157 ml, 1 overflow flask, 428 ml, 1 bottle, 50 ml potassium hydroxide solution, 1 bottle, 50 ml nitrification inhibitor solution, 1 instruction.