Waste water respirometry solutions for toxicity testing

If industrial wastewater entering a treatment works contains toxic components the rate of biodegradation will be inhibited or stop completely. This can result in failed consents and will certainly give rise to operational problems. Visible indications include deflocculation, bulking and the appearance of filamentous bacteria. Sometimes, there are no visible effects. When the sludge bacteria are inhibited, there is the possibility of toxicity carryover in the effluent that is discharged to receiving waters. With new environmental legislation being introduced, worldwide, to protect the natural environment, toxin discharge is now a serious concern for treatment plant managers.

Toxicity, therefore, results in:

  • Increased costs of treatment
  • Failure to comply with discharge consents
  • Financial penalties for discharging toxic effluent

In order to protect a treatment works, from unknown toxic influents entering by sewer, a toxicity management regime is required. Tests with a laboratory respirometer are then required to measure the toxicity of the effluent, in order to determine the safe rate of discharge into the aeration tanks. For tankered waste, laboratory tests on samples of the wastewater are carried out prior to its acceptance for treatment. Manufacturing companies who treat their own waste and are concerned to minimise treatment costs, use the respirometer to monitor the toxicity of effluent streams. In this way, discharge rates can be controlled in order to ensure that toxicity does not inhibit the activated sludge bacteria of the aeration tanks.