- In Germany, industrial wastewater treatment is subject to the strict provisions of the Waste Water Ordinance (Abwasserverordnung). Improper, insufficient treatment can lead to the shutdown of an entire treatment plant until the deficiencies are remedied.
- Treating industrial wastewater is much more than complying with environmental regulations. Plants with high water consumption lower the cost of the raw material by treating and re-using their wastewater.
- For organic wastewater treatment in particular, precise measurements of pH values, oxidation-reduction potential (ORP), and dissolved oxygen are essential for ensuring the optimal metabolism of the bacteria used for purification.
Monitoring pH, ORP, and oxygen for environmentally sound wastewater treatment
Unlike the service water of private households, industrial wastewater is polluted by substances that are difficult to decompose. Depending on the sector, they could be heavy metals, grease, oil, alkaline substances or, as in the paper and soap sectors, organic substances that can only be neutralized or separated with great effort. Alongside mechanical filtration methods, thermal processes as well as microorganisms are used to purify it.
pH measurement to protect plants and bacteria
Depending on the level of contamination, organically contaminated wastewater goes through different purification processes, including flocculation and precipitation. During flocculation, the dissolved harmful substances are clotted to form flakes that can be filtered. Precipitation has the goal of restructuring the harmful substances into heavier compounds that drift down to the bottom. If the wastewater cannot be classified as harmless after these treatments, bacteria convert the remaining contaminants into flammable or recyclable biomass in aeration tanks.
Service water or cleaning water from food and beverage production or fermentation processes has highly variable pH values depending on the application. Since low pH values can damage plant components or kill bacterial cultures, recording the pH values in feed lines is a timely countermeasure. pH values that are too high or low can be neutralized by adding chemicals or if necessary, the wastewater feed into clarification tanks can be interrupted. Because it is dimensioned for extreme pH values, the SE 554 Memosens sensor is ideal for wastewater monitoring in the food and beverage industry. Its material, Alpha glass, ensures quick, stable sensor response. Direct contact to the polymer electrolytes via an open junction reliably prevents problems caused by clogging and blockage in heavily contaminated media.
Underwater measurement for ventilation control
ORP is an important parameter for efficiently ventilating the aeration tank. In combination with other process variables, it provides useful information on the ratio of oxygen content to bacteria activity. As a sum parameter, ORP does not indicate an absolute quantity of substance. Instead, it enables the continuous measurement and observation of changes in concentration over time. Comparing concentration trends to other values yields a basis for controlling tank ventilation, with which maximum efficiency of aerobic and anaerobic metabolism phases can be achieved. Experience has shown the most useful measurement results come from the upper 25 percent of the water in the tank. Measuring electrodes must be immersed to reach this level, and the SE 565 Memosens sensor has proven itself for ORP measurement. Due to their inductive transmission of supply voltage and digitized measured values, Memosens sensors can be utilized effectively under water. They are additionally suitable for use in aggressive or highly contaminated media, and media containing sulfides or proteins. In order to ensure that aerobic microorganisms have a sufficient supply of oxygen, absolute measurements of dissolved oxygen concentration are required. The SE 715 is an affordable Memosens sensor for the simultaneous measurement of dissolved oxygen and temperature. It was specially developed for aeration and ventilation control in wastewater treatment plants. Alongside long-term stability and quick sensor response, its most outstanding features include low flow dependence.
The sensors can be integrated into the process in open tanks with the help of immersion fittings. Up to three 12-mm sensors can be mounted in the ARD 75 immersion fitting (pH/ORP, conductivity, oxygen) at the same time. Quick sensor replacement with sensors that are pre-calibrated in the laboratory and an integrated sensor rinsing function are additional features that make it ideal for use in wastewater treatment plants.
Return on Investment
- Thanks to inductive, waterproof Memosens connectors, the sensors can be used to measure pH values, ORP, and dissolved oxygen directly at the required measuring point – without any additional equipment.
- Forgoing conventional process adaptation lowers the costs and effort of replacing sensors.
- The high quality of measurements taken below the water line and reliability of Memosens sensors, which are known for their long-term stability, improve overall process quality.