ORSANCO Adopts Total Dissolved Solids Water Quality Criterion

Last year the Ohio River Water Sanitation Commission (ORSANCO) proposed adopting a water quality criterion for total dissolved solids (TDS) of 500 mg/L, but the decision was suspended  temporarily while the Commission worked out a procedural issue.  That has now been resolved and the standard has been adopted. The following is found at page 11 of the 2011 Pollution Control Standards:

 

D. Taste and Odor Protection

To protect drinking water supplies from adverse taste and odor, the following

criteria shall be met at Ohio River drinking water intakes:

TOTAL DISSOLVED SOLIDS: Concentration shall not exceed 500 mg/L at

river flows equal to or greater than the minimum 7-day, 10-year flow.

TDS. Ordinarily, water quality standards must be met at the discharge point or at the edge of a mixing zone, within a few hundred feet downstream of the discharge pipe.  In that case, the permit  writer sets the permit limit of a pollutant after calculating how quickly the pollutant will be diluted once it is discharged, in order to avoid any concentration of the pollutant above water quality standards near the discharge.  With TDS, the permit writer would only look to see whether the discharge would cause a violation of the TDS standard at the drinking water intake downstream.  The TDS from any individual discharge likely will be well-mixed with the river before it reaches a drinking water intake, and therefore won't contribute to any problems at the intake.  As a result, this new criterion should not result in many new permit limits for TDS.

ORSANCO sets water quality standards for the Ohio River.  The standards apply to the Ohio River, in addition to the standards adopted by any other state that borders the Ohio River.