by Kristin Taormina
 
 

Think about the last time you had a check-up at the doctor’s office. The doctor probably checked your blood pressure, took your temperature, and made you say “ahhhh.” Then the fun part: being poked for a blood test. Much like a doctor draws from our bloodstreams to test our health, a wastewater treatment plant  operator should be sampling from his influent and effluent streams to monitor the health of his wastewater treatment system.

Anyone operating a production plant that generates a wastewater needs to have a sound understanding of wastewater monitoring, sampling and testing practices. Whether for regulatory consideration (demonstrate discharge compliance) or economic consideration (establish surcharge costs or track the value of lost product), sampling and testing are critical to your operation. In addition, considering that every sample that is collected and sent to a certified lab for analysis costs an average of $20 to $30 per parameter analyzed, you need to be assured that you will obtain accurate and reliable results.

Although facilities often take care to sample and report parameters that are regulated, such as the final effluent, sampling and monitoring streams within the wastewater treatment system are equally important to maintaining the health and efficiency of the system.  The raw influent stream(s) to a wastewater treatment plant define the loading to the plant and can serve as an indicator of production plant problems.  As a minimum, it is recommended to monitor BOD/COD, TSS, NH3, phosphorus, and daily flow, regardless of the type of treatment.  

Individual treatment processes within a wastewater treatment plant also benefit from regular sampling and monitoring, such as the following:

• Primary and secondary clarifier influent flow and influent and effluent TSS can define the solids loading rate and surface overflow rates, as well as the solids removal efficiency.  
• Activated sludge systems require regular monitoring of MLTSS, MLVSS, dissolved oxygen (DO), and temperature.  
• Anaerobic systems require regular monitoring of flow, temperature, TSS, VSS, BOD, and COD to define loading rates and removal efficiencies.  
• Nutrient needs for biological systems can be checked by testing for NH3 and other phosphates.
• Biogas utilization systems benefit from gas flow, percent methane, H2S, and siloxane sampling and monitoring.  
• Waste and return sludge systems should be monitored for flow, TSS and VSS as a minimum.  
• A variety of other processes may exist in a treatment system in which one must evaluate what parameters define proper and efficient operation.   

                  
While it is ideal to sample for many parameters within a wastewater treatment system, the cost of sampling often prohibits the practice.  For parameters that are not regulated, consider in-house testing.  COD is one parameter that can be economically tested in-house for a cost of about $2 per test.  The cost of lab equipment and labor must be weighed against the cost of outside laboratory testing.  Often times, routine monitoring and data collection do not take place even when instrumentation is in place.  A sampling and monitoring plan needs to be defined and followed by plant staff.  Refer to that dusty plant O&M manual if need be!  In addition, organized data collection and tracking are essential for plant performance and health.    

Sampling of a wastewater stream seems easy, but keep in mind the following guidelines:

• Double-check the source of the wastewater to be sampled. Is it really the one you need to characterize?
• Determine if grab, time-composite, or flow-composite samples are required, and then select the proper sampling equipment.
• Verify that the sampling frequency meets your needs (hourly, daily, or longer term).
• Use the proper sample container (e.g., glass for fats, oils, and grease) and preservatives (e.g., nitric acid for copper).
• To obtain the most accurate results, refrigerate samples until shipped/transferred in chilled containers to the testing laboratory.
• Testing of the samples can be more complicated than collecting them.  Some guidelines to follow include:
• Whenever possible, run all tests according to the latest edition of Standard Methods, such as the 20th Edition of Standard Methods for the Examination of Water and Wastewater.
• For onsite testing, follow an established procedure consistently and precisely. Always calibrate instruments with known and current standards.
• For offsite testing, be sure to work with a certified laboratory. Occasionally split a sample between  certified laboratories and compare the two sets of data.

Please contact ATI for more details on the guidelines of monitoring, sampling and testing or sample collection containers and preservatives.