Organic measurement is one of the factors used to determine wastewater quality!
Organics is the assessment of the concentration of carbon-based (i.e., organic) molecules with the goal of determining the relative "strength" of wastewater (e.g., Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and Oil and Grease (O&G).
How to measure BOD and COD?
If the BOD concentration in a treated effluent is consistently greater than 110 mg/l and COD concentration in a treated effluent is consistently greater than 250 mg/l before disposal to any receiving body, such industrial units must identify the chemicals causing the same, according to BIS.
BODis measured using Standard Procedures IS: 3025-Part 44 'Methods of sampling and testing (physical and chemical) forwater and wastewater (BOD)’.
CODis measured using Standard Procedures IS: 3025-Part 58 'Methods of sampling and testing (physical and chemical) forwater and wastewater (COD)’.
BOD and COD measuring units
Analytical studies aiming at determining the concentration (usually in mg/L or ppm) of organic (i.e., carbon-containing) matter in a wastewater sample have historically been used to evaluate the relative "strength" of the sample.
BOD measurement technique
A wastewater sample is required to guarantee optimal biological activity during the BOD test. It must be chlorine-free. If there is chlorine in the sample, a de-chlorination agent (such as sodium sulphide) must be applied before testing.
The pH should be between 6.5 and 7.5. If the sample falls outside of this range, acid or base must be supplied as necessary.
A sufficient microbial population must already exist.If the microbial population is insufficient or unknown, a "seed" solution of bacteria is introduced along with an important nutrient buffer solution to ensure the viability of the bacteria population.
Specialized 300 mL BOD bottles are utilized, which enable for complete filling with no air space and ensure an airtight closure. The bottles are filled with the test sample or dilution (distilled or deionized) water, then varying volumes of the wastewater sample are added to represent different dilutions. As a control or "blank", at least one bottle is filled just with diluting water.
The initial dissolved oxygen concentration (mg/L) in each bottle is measured using a DO meter, and it should be at least 8.0 mg/L. Each bottle should be then put in a 20°C dark incubator for five days.
After five days (three hours), the DO meter is used again to determine the final dissolved oxygen concentration (mg/L), which should be less than 4.0 mg/L.
The BOD concentration (mg/L) is calculated by subtracting the final DO value from the starting DO reading. The BOD concentration value is multiplied by the dilution factor if the wastewater sample requires dilution.
COD measurement technique
A series of recognized standards are developed using KHP prior to finishing the COD test. Because the majority of wastewater samples will be in the high range, standards of 100, 250, 500, and 1000 mg/L are routinely developed.
A COD reactor/heating (150°C) block and a colorimeter are both activated to allow both instruments to stabilize.
The COD test uses pre-prepared low-range (3-50 ppm) or high-range (20-1500 ppm) vials based on predicted findings. If the predicted outcomes are unknown, any range can be chosen.
One vial is labelled "blank," and the other three or four are labelled with recognized standard levels. The wastewater sample is then divided into two vials for a duplicate run.
It should be noted that when several wastewater samples are collected, at least 10% of the samples are duplicated.
Each vial receives 2 mL of liquid. 2 mL of DI water are supplied in the case of the "blank." 2 mL of each standard is added to the appropriate containers. If the wastewater sample is analysed at its full strength, 2 mL is added to the appropriate container. If dilution is necessary, serial dilutions are conducted, followed by the addition of 2 mL of the diluted material to the matching vial.
Each vial is well mixed before being placed in the reactor block for two hours. The vials are withdrawn from the block after two hours and placed on a cooling rack for roughly 15 minutes. The colorimeter is adjusted and calibrated in accordance with the unit's particular instructions (i.e., appropriate wavelength, blank, and standards), then each vial is inserted in the device and the COD concentration is read.
What do we have to offer? Why are we writing about BOD and COD?
The World Health Organization as well as BIS specifies the standard values for both BOD and COD before disposing the wastewater of in the surface or inland waters. As STP/ETP/WWTP/WTP manufacturers, we can provide you with expert solution and design the best suited treatment plant as per your needs with BOD and COD values in mind.