1. The sensor measures the turbidity (amount of suspended particles) of the treated water in a sewage treatment plant.
2. High turbidity indicates higher suspended particles present in the treated water after the filtration process.an optical sensor for sewage treatment plant is a measuring tool for a turbid water density or an extraneous matter concentration using the refraction of wavelength between photo transistor and diode.
3. High turbidity indicates higher suspended particles present in the treated water after the filtration process.

1. Oxidation-reduction potential (ORP, redox) is one of the methods to measure the rate of oxidative disinfection caused by the addition of the effects of all oxidants in the water (eg: chlorine dosing).
2. ORP offers real time monitoring and recording of water disinfection potential.
3. A primary advantage of using ORP for wastewater system monitoring provides the operator with a rapid and single-value assessment of the disinfection potential of the treated water.

https://www.cpcb.nic.in/openpdffile.php?id=TmV3c0ZpbGVzLzY4XzE1MzEyMzM3OTZfbWVkaWFwaG90bzcwNTAucGRm

No, CPCB neither certifies nor assessed any sensors/ analysers. Industrial units are free to choose any type/ make of analysers including the indigenous equipment, meeting the prerequisites. The unit should give calibration protocol, periodicity/ frequency of calibration and ± variation specified when matched with manually monitored results.

The biochemical oxygen demand (BOD) is a measure of the oxygen required by aerobic micro-organisms to biochemically oxidize the organic matter present in the waste and is expressed in mg/1.

The chemical oxygen demand (COD) is a measure of water and wastewater quality. The COD test is often used to monitor water treatment plant efficiency. The COD is the amount of oxygen consumed to chemically oxidize organic water contaminants to inorganic end products.

COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. this includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing.