Maintaining consistent, compliant wastewater discharge at all times is vitally important since wastewater treatment plants operate 24 hours per day, seven days a week.
Official discharge permit sampling is required periodically, but it is equally important to maintain consistent wastewater discharge compliance at all times.
Wastewater treatment procedures may also need to be modified from time to time in response to instantaneous changes of the incoming untreated wastewater. This is extremely important for an operator to achieve. However, permanent changes sometimes affect the quantity and the quality of the untreated wastewater, and they may require permanent procedure changes to satisfy discharge permit limits. Ongoing procedures may also need to be changed.
An industrial customer recently asked me to monitor the significant changes of untreated wastewater and report the impact, cost, procedures, treatment requirements, etc., to management.
This article covers the data utilized to analyze the untreated wastewater’s changes and it identifies some of the required procedure modifications to respond to those changes while taking into account the maintenance required to consistently comply with the wastewater discharge permit.
Examples
When we started receiving the untreated wastewater, the first issue we identified was a substantial reduction in the volume of untreated influent.
As it worked out, the volume of water decreased almost 50 percent. This reduction was also important in terms of flow rate fluctuations. Because we were operating without an equalization tank, we had to react quickly to current rate changes and to the instantaneous changes during the treatment cycle.
The next obvious issue was that the absorption of the pollutants in the untreated wastewater was also diminished.
Decreases in volume and decreases in concentrations can show how wastewater treatment procedures and the individual process units work in physical/chemical wastewater treatment.
Changes in operating procedures would probably need to be linked with chemical set point changes and perhaps the unique chemicals used.
Current procedures
An analysis of current operating procedures for untreated wastewater would help operators understand how to modify any existing wastewater treatment process units’ operating procedures to meet untreated wastewater treatment volume and concentrations.
To better interpret the circumstances behind changes to these procedures, it is beneficial to understand the current wastewater treatment operating procedures before the changes take place.
For the current procedures, the incoming untreated wastewater flows through a circular screen. After a couple of pH adjustment locations, a polymer solution — flocculant — is injected into the flow stream before entering a solids separation process unit.
The effluent treatment process concludes with a pH adjustment procedure to satisfy discharge permit compliance as effluent flows to the sewer collection system.
Procedure modifications
After the alterations to the untreated wastewater occurred, we determined that we could reduce the amount of chemicals for treating each gallon of wastewater.
We used three basic chemicals for treating wastewater. After the changes, we were able to decrease the intensity of each chemical by approximately 60 percent, which was larger than the 50 percent reduction in the mass amount of untreated influent.
An analysis of the sludge generated from the decreased volume of untreated wastewater revealed a substantial reduction in sludge volume. The mass of sludge decreased by more than 65 percent. Perhaps this significant decrease of sludge volume was caused by a 50 percent decrease in untreated wastewater and a 60 percent decrease in chemicals used with the untreated influent. The reduced mass of sludge allowed for significant modifications to the solids handling processes.
In summary, we found that we could convert the pH set points throughout the treatment process and reduce the mass of chemicals used at each of the chemical injection locations, which afforded us these decreases throughout the treatment procedure.
Conclusion: Improved discharge
Measurement of the wastewater treatment operating procedures and wastewater treatment solutions revealed that with decreased quantity and quality of untreated wastewater, it was advantageous to control with fewer chemicals. Laboratory analysis results were essentially equal to the results achieved before the untreated wastewater changes.
Ultimately, consistent quality wastewater discharge was maintained at a reduced cost per unit of untreated wastewater because each gallon of untreated wastewater had a reduced waste load.
Known in the industry as "Wastewater Dan," Dan Theobald, proprietor of Environmental Services, is a professional wastewater and safety consultant/trainer. He has more than 24 years of hands-on industry experience operating many variants of wastewater treatment processing units and is anxious to share his knowledge with others.
