How do we characterize wastewater?
If you need to treat a major wastewater stream, the main step is usually to use a biological process. This is because it is one of the cheapest complete treatments and produces a relatively small amount of waste. However, the types of pollutants present in the wastewater tend to be very selective in the type of pollutants removed and must be determined to assess the suitability of one treatment for another.
Why do we need to characterize wastewater?
To identify the type of pollution, it is necessary to characterize the wastewater. This provides a wide range of information on the types and concentrations of pollutants present. In addition to general parameters such as pH and conductivity, parameters that provide information on organic content, nutrients (nitrogen and phosphorus), suspended solids, wastewater toxicity to microorganisms, and related more specific to determine.
How to identify wastewater characteristics?
Biochemical oxygen demand (BOD-5) is often used to characterize wastewater to determine the amount of organic matter that microorganisms can absorb. Each measurement requires at least 5 days, which is not practical to use for processing plant management.
In contrast, chemical oxygen demand (COD) is an accurate parameter that can be easily determined and measures all organicmatter (both biodegradable and non-biodegradable) present in water. Therefore, it is the most widely used. However, the information provided is necessary just because it measures all organic matter, but it is not enough to better understand the wastewater being treated.
To get complete and detailed characteristics of the process, in addition to measuring the above parameters, it is necessary to run COD fractions that provide information on different decomposition rates of different COD fractions.
The generally considered COD fraction is that used in the “Activated Sludge Model of the International Water Quality Association (IAWQ)”.
1: Biodegradable COD (rbCOD)
This fraction, corresponding to water-soluble COD is consumed fastest (within minutes) by biomass, creating rapid and high oxygen demand. The compounds contained in this fraction are soluble low molecular weight substances such as sugars, alcohols and fatty acids.
It is that one which slowly biodegrades. This fraction is associated with insoluble biodegradable or particulate COD and is usually the largest biodegradable fraction. It is composed of soluble high molecular weight molecules, colloidal substances, and solid particles, all of which are not easily degraded by biomass. They must first be hydrolysedby enzymes secreted by microorganisms and converted to soluble low molecular weight molecules that can be easily taken up by cells. This hydrolysis step is slow, the rate-determining step of the process, and is associated with much lower oxygen consumption than is observed in easily biodegradable COD.
3: Soluble non-biodegradable COD (snbCOD)
This fraction is unaffected by contact with biomass, does not change during treatment, and is discharged with wastewater. If this is the largest percentage of wastewater, biological processes can be excluded directly.
4: Particulate non-biodegradable COD (pnbCOD)
Although not consumed by biomass, most of this fraction precipitates with sludge, thereby reducing its outflow concentration compared to the inflow concentration.
Different fractions are best determined by respiratory measurements, as soluble COD corresponds to COD that is easily biodegraded and particulate COD does not correspond completely to COD that is slowly biodegraded. This technique measures the oxygen consumption of biomass as it decomposes over time, thereby providing highly accurate information about microbial activity and the rate at which various substrates are consumed.
Role of Netsol Water!
These characteristics are required to be carefully studied and then manage operations at the wastewater treatment facility.
We at Netsol Water have more than 10 years of experience in waste water treatment plant manufacturing and operations. For water, wastewater or sludge treatment, we offer a complete spectrum of wastewater treatment products. Our engineers would gladly collaborate with your team to create the right design that meets your budget and objectives.