virulence dilution factor determination

Determination of toxicity dilution factor
Determination of toxicity dilution factor

The Ministry of Environment and Forestry issued the Communiqué on Sampling and Analysis Methods for Water Pollution Control Regulation in 2009. This Communiqué regulates the principles for the determination of the quality of the waters and for the continuous or intermittent inspection of wastewater and receiving environments in the discharge of domestic and industrial wastewater or discharge to receiving environments. In addition, the principles regarding the measurement and analysis methods of the quality parameters stipulated in the Regulation on Water Pollution Control are also included in these audits.

The toxicity dilution factor determination studies to be carried out in these inspections are explained in the annex of the mentioned Communiqué titled Table 1 Toxicity Dilution Factor (ZSF) Determination (Appendix 1).

Physical and chemical methods alone are insufficient to assess the effects of pollutants on aquatic organisms. Therefore, toxicity tests are carried out to determine water pollution.

The wastewater contents adhere to the fins of the fish and cause swelling and disintegration of the respiratory tissues. In this way, the fish are damaged. In addition, harmful substances taken with fins, fish skin and digestive systems into the poisoning is caused.

This poisoning effect in wastewaters is also determined in proportion to the volume in which wastewater is diluted with dilution water. Accordingly, the smallest dilution value that all fish can survive is based on and the poisoning effect of wastewater is expressed by the dilution factor (ZSF).

Dilution factor = Unit wastewater volume + Volume of dilution water depending on wastewater volume used

Briefly, the dilution factor refers to how many volumes of wastewater are diluted with how many volumes of dilution water. For example,

Dilution factor (ZSF) 5 = 1 volume wastewater + 4 volume dilution water

The smallest value of the dilution experienced by all fish is called the Toxicity Dilution Factor (ZSF).


Toxicity Dilution Factor (ZSF) determination in wastewater is carried out by authorized laboratories within the scope of chemical food analysis. In these studies, standards and test methods issued by national and international organizations are followed.