Environmental standards - BOD, TOC, COD, TSS and TDS Standards

The organic strength of wastewater is measured in three ways: 1) as 5-day biochemical oxygen demand (BOD5), 2) chemical oxygen demand (COD), and/or 3) total organic carbon.

Typically, municipal wastewater treatment plants will use BOD5 as a measure of the organic concentration into, and through, the wastewater plant. Industrial wastewater systems will more often use COD to measure the organic concentration moving through the treatment plant.

CRMs for BOD5 testing

GGA Snips™ were designed to help reduce the incidence of a non-conforming GGA (Glucose-Glutamic Acid) test in the wastewater lab. Several potential issues with a GGA standard can contribute to the incidence of GGA non-conformance. The design and use of our GGA snip prevents these issues:

  • GGA Snips™ are always formulated from certified highest purity chemicals using a validated standardized procedure. This prevents problems that may result from lot to lot variance due to inadequately controlled raw materials.
  • GGA Snips™ are analytically certified for formulation accuracy against a NIST SRM assuring you not just of the solution accuracy, but also providing you a valuable link to SI.
  • GGA Snips™ are analytically certified for formulation accuracy against a NIST SRM assuring you not just of the solution accuracy, but also providing you a valuable link to SI.
  • GGA Snips™ are packaged for single use preventing inadvertent cross-contamination in your lab.
  • And finally, GGA Snips™ are sterilized in the tube after packaging. This prevents un- recognized microbial degradation making the GGA snip stable for more than 3 years when stored at room temperature.
GGA snips
GGA snips

CRMs and RMs for Total and Free Residual Chlorine

Pipetting and cumbersome dilution schemes are impractical in certain water and wastewater testing situations, NSI Lab Solutions Chlorine Snips™ are the most convenient reference material for residual chlorine analysis on the market.

  • They require no pipets and no glassware other than the instrument cuvette to prepare.
  • Chlorine Snips™ are ideal for use at testing points remote from the fixed base laboratory.
  • To use a Snip™, simply open the tube with a pair of scissors and transfer its contents to your cuvette and bring to volume with reagent water. CRMs for residual free chlorine are packaged in flame sealed ampules.

Available at 6 different concentration levels and the dilution scheme for each to always be 1:1000.

Chlorine SnipsTM and chlorine CRMs are applicable to both drinking water and wastewater testing. NSI internal certification protocol includes both total and free residual chlorine with values for both documented on accompanying COA.

TOC: Total organic carbon (TOC)
Is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality.
A typical analysis for total carbon (TC) measures both the total organic carbon (TOC) present and the complementing total inorganic carbon (TIC), the latter representing the amount of non-organic carbon, like carbon in carbonate minerals.
Subtracting the inorganic carbon from the total carbon yields TOC. Another common variant of TOC analysis involves removing the TIC portion first and then measuring the leftover carbon.
This method involves purging an acidified sample with carbon-free air or nitrogen prior to measurement, and so is more accurately called non-purgeable organic carbon (NPOC)

COD Test:
The Chemical Oxygen Demand (COD) test uses a strong chemical oxidant in an acid solution and heat to oxidize organic carbon to CO2 and H2O.
By definition, chemical oxygen demand is “a measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant.”* Oxygen demand is determined by measuring the amount of oxidant consumed using titrimetric or photometric methods.
The test is not adversely affected by toxic substances, and test data is available in 1-1/2 to 3 hours, providing faster water quality assessment and process control. COD test results can also be used to estimate the BOD results on a given sample.
An empirical relationship exists between BOD, COD and TOC. However, the specific relationship must be established for each sample. Once correlation has been established, the test is useful for monitoring and control.

Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus.
It is a water quality parameter used to assess the quality of a specimen of any type of water or water body, ocean water for example, or wastewater after treatment in a wastewater treatment plant.
Total dissolved solids (TDS) is another parameter acquired through a separate analysis which is also used to determine water quality based on the total substances that are fully dissolved within the water, rather than undissolved suspended particles.