(554d) Experimental Orders on an Entrepreneurial Pace: Dairy Wastewater Characterization Control Using Sequenced Blending

A creative mindset must be adopted in the effort to create sustainable processes.  Whether it be a process improvement to an existing technology or a novel application of sustainable processing, screening the effects through experimental orders often must be done in a fast pace environment with limited information.  The case study presented is dairy wastewater control applying an entrepreneurial mindset to practical experimental orders. 

Discharge specifications for effluents to the POTW have pH as a significant regulatory compliance component.  Many small to medium cheese plant operations discharge directly to the POTW.  Usually, cheese and milk products are produced in the same plant.  There is both acidic and basic cleaning solution discharge streams.  By using a selective blending control system the effluent from the plant to the POTW can be modified in process and in some cases water can be recovered for other operations.  Cycling of the cleaning operations is not practical with the pressures upon production.  The installation and use of pH monitoring and flow control systems can temper the blended discharge.  pH curves can be determined to assess the capacities of both the basic and acidic fluids to accept volumes of the other for in process neutralization.

Cheese whey is acidic.  Samples are in the pH 4 – 5 range.  The high pH cleaning residue can accept cheese whey as an effluent constituent.  Whey residue contains calcium which will precipitate as the pH is raised.  The baseline pH variability of the current effluent treatment system can be established and translated to a bench lab titration.  The cheese whey was characterized and added in a mass ratio to the available effluents then titrated similarly to the current system.  The pH neutralization curves were established for each of the three loading levels.  The family of curves were used to establish the mass balance expected at full scale  Sample analysis was conducted at the nominal operating temperatures.

Typically high pH characteristic flow can accept up a mass of the cheese whey without dropping the pH below 10.  This condition could occur frequently.  A sequenced blending control scheme would control of the cheese whey addition should be programmed to occur only when the waste tank material has the capacity to accept the cheese whey.  A second waste tank characteristic with a lower pH in the range of 7 – 9 was also observed.  It did not have capacity to neutralize the added cheese whey.  The sequenced blending control scheme will be needed to avoid this possible out of specification condition.

The addition of cheese whey may require additional caustic neutralization.  This may add additional precipitates to the existing waste stream.  The pH neutralization kinetics could be effected by the formation of additional precipitates.  The mixing parameters can be validated by lab work in sample jars and beakers.  These indicative results can then be run in a scalable mix system.  Effects of mixing on the reaction kinetics can be difficult to observe in small lab volume samples.