One of nature's most valuable resources is water. Groundwater is necessary for plant and animal life to survive, as well as a raw resource for many industries. Wastewater is contaminated water that must be processed for reuse or safe disposal due to human activity, environmental factors, or industrial activities.
What is dissolved oxygen?
The amount of gaseous oxygen dissolved in a sample of water is referred to as dissolved oxygen. Oxygen can be absorbed directly from the atmosphere or indirectly from nearby plants as a by-product of photosynthesis.
What is chemical oxygen demand (COD)?
The amount of oxygen required to oxidize all soluble and insoluble organic molecules present in a volume of water is known as the Chemical Oxygen Demand (COD). The concentration of COD is commonly measured in milligrams per liter of water (mg/L).
Typically, chemical oxygen demand measurements are performed on wastewater. The amount of organic matter in the water is used to calculate the pollution level. Water containing too much organic material can harm the environment where the effluent is dumped.
Importance of COD for wastewater:
Chemical Oxygen Demand is an important parameter to check the quality of the water because, like BOD, it provides an index in order to determine the impact of discharged wastewater in the river streams or other waterbodies where it is discharged. Higher COD levels indicate that the sample contains more oxidizable organic material, lowering the dissolved oxygen (DO) levels. Anaerobic conditions can result from a reduction in DO, which is harmful to higher aquatic life forms. Because of the reduced testing period, COD is frequently used as a substitute for BOD.
Applications of chemical oxygen demand in wastewater treatment:
COD has four significant applications in wastewater treatment:
1. To evaluate the amount of oxidizable contaminants in wastewater.
2. To use as a metric to assess overall water quality.
3. Determine the efficacy of wastewater treatment options.
4. To estimate the impact of wastewater disposal on the ecosystem receiving the wastewater.
How to reduce cod in wastewater?
COD reduction in wastewater management can be accomplished in a variety of ways. The following are two of the most prevalent methods for removing COD from wastewater:
1. Wastewater separation
Coagulation and flocculation are wastewater treatment processes that remove colloidal particles present in wastewater.
Coagulation involves adding a non-toxic solution to make chemicals to the water, such as ferric chloride (FeCl) or alum, to gather all the dispersed particles together into clumps that can be easily collected from effluent by filtration.
Flocculation is a method of removing clumped particles from water by creating bigger particles, or flocs, using a chemical polymer (flocculating agent). The flocs are subsequently placed into a sedimentation tank for further treatment before being disposed of, as part of the wastewater treatment process.
Using coagulants and flocculants to remove organic debris from wastewater decreases the 'food' required for bacteria to grow, lowering the competition for dissolved oxygen with marine life.
2. COD removal by microbial action
Incorporating bacteria or microbes that break down organic compounds in wastewater is another effective COD reduction method. In sewage treatment, microbes can be aerobic or anaerobic.
In the presence of air, aerobic COD removal introduces microorganisms or bacteria that break down organic components in wastewater into carbon dioxide and water. Aerobic COD removal is best for wastewater with a COD concentration of less than 3000 mg/L.
In the absence of oxygen, anaerobic COD removal uses bacteria to convert organic molecules in wastewater to biomass. It is a very advantageous technology since the ethanol produced can be used as an alternative energy source for electricity, heating, and drying applications. Anaerobic COD removal is appropriate for wastewater with a COD concentration of more than 2000 mg/L.
For more information, contact Netsol Water!