APPLICATION OF JUMO DISSOLVED OXYGEN SENSORS ON THE AEROTANKS OF TREATMENT PLANTS

To remove mineral and organic pollutants from the clarified water, the biological treatment stage is implemented at the sewage treatment plants.
The biological treatment of the pollutants is carried out in the aerotanks. The wastewater contacts active sludge organisms therein with the appropriate amount of dissolved oxygen, followed by separation of activated sludge from the purified water in the settling tanks.
The function of active sludge is biological oxidation of organics in the wastewater to simple compounds and sorption.
The most important factor, affecting the development and viability of the active sludge, and the quality of biological purification, among others, is the content of dissolved oxygen.
The saturation with oxygen occurs in the process of lifting of the air bubbles to surface and gas lift effect, which forms the ascendant fluid flow, creating circulation around the aerotank section. The rated value of oxygen concentration comprises 2 mg/l in any point of the aerotank.
Given the fact that the volume and composition of the wastewater varies continuously and depends on the daytime, the operational control of the aerotanks can reduce the energy consumption and improve the quality of wastewater treatment.
Monitoring of content of dissolved oxygen in the aeration tank, using chemical laboratory resources, unfortunately, is not possible, as it can be carried out not more than 1-2 times per day, while the oxygen concentration depends on many parameters and is constantly changing.

Thus, to control the air supply into the aeration tank by the dissolved oxygen content, it is necessary to use the in-line stationary oxygen sensors. With JUMO sensors you can not only continuously monitor dissolved oxygen in the aeration tanks, but also automate the adjustment process.
Today, the amperometric and optical types of dissolved oxygen sensors are the most common. Both types of sensors are included in JUMO supplies program.

Amperometric sensors have an attractive price, but they have the disadvantage, they require regular and time-consuming maintenance.

To determine the dissolved oxygen in the aeration systems by amperometric method, JUMO offers to use dTRANS O2 01 — double-wire measuring transducer of dissolved oxygen concentration (DO).

Features:

• simple, reliable service by replacing the unit
• reliable one-point calibration
• two-wire transmitter
• galvanic isolator of measuring (DO) and output signals (mA)
• direct connection to the existing units (e.g., CPCS)
• maximal performance design can be used as a stand-alone solution
• compensation by temperature, air pressure and salinity
• setup-program for easy configuration and documentation of the measuring point
• graphic display background light
• wide range of accessories

Two-wire measuring transducer JUMO dTRANS O2 01 is designed to measure concentrations of dissolved oxygen in water solutions. It outputs galvanically isolated output signal of 4 ... 20 mA proportional to the content of dissolved oxygen. With the setup-program or optionally supplied control panel, the instrument configuration can be changed. The temperature of the medium can be determined with Pt1000 resistance thermometer, and in the standard and maximum performance design it can be also converted into two-conductor signal of 4 ... 20 mA. The measurement is performed by electrochemical sensor covered with a diaphragm. The built-in microprocessor circuit takes into account the factors of temperature, air pressure and salinity (salt content). The sensor itself is made in the form of module and can be easily maintained and replaced.

Optical oxygen sensors are more expensive and allow not only to enhance reliability and accuracy of measurements, but also to refuse the consumables, and to minimize maintenance.
To determine the dissolved oxygen in the aeration systems by optical method, JUMO offers to use optical sensor ecoLine O-DO.

Features:

• low maintenance costs during operation
• high measuring accuracy at low concentrations
• quick response time
• compensation by temperature, air pressure and salinity
• wide range of accessories

Optical sensor JUMO ecoLine O-DO is designed to measure concentrations of dissolved oxygen in water solutions. Thanks to built-in preamplifier and digital signal processing circuit, the sensor has high interference resistance. The built-in microprocessor circuit takes into account the factors of temperature, air pressure and salinity. The replaceable optical sensors reduce time required for sensor maintenance. The calibration data are saved right in the sensor. The integrated Plug and Play system eliminates the necessity of re-calibration.