The day began with Dave Johnson, Merrill City Administrator, welcoming us and the attendees to Merrill. He shared that he started his professional career at the wastewater treatment plant in Indianapolis and finds this industry and professions as one of the most important. He strongly recommended that we spend a lot of time (and money :)) in Merrill.
Richard Fulk, Rivers Bend Engineering, was the first speaker. He covered the fundamentals of industrial wastewater pretreatment. The treatment of industrial wastewater goes through equalization, chemical treatment, phase separation, and final polishing. The main difference between industrial and municipal treatment is that industrial treatment utilizes chemical treatment instead of biological treatment.
After a break, biological upsets, defined as anything that limits the biological process, were discussed by Troy Larson, Strand Associates. Potential causes, users, and symptoms were identified. There are action steps that should be taken before (know your industry, permit, ordnance, develop a baseline), during (isolate impacted influent, contact appropriate entities, adjust process, document activity, consider reseeding, attempt to identify source), and after (document, implement lessons learned) a biological upset. Several case studies were discussed.
Mark Duer, Mulcahy/Shaw Water, next spoke about industrial pretreatment flow monitoring and sampling. He gave an overview of both time proportional composite samplers and flow proportional composite samplers. For flow proportional samplers, a primary device (wier or flume) must be selected, each type having advantages and disadvantages. He also discussed types of secondary measuring devices, including open channel flow meters, ultrasonic, bubblers, velocity meters, and submerged probes.
There was a short break, and then Steve Ohm gave the brief DNR update. After this, Terry Vanden Heuval discussed the successful implementation of Merrill’s industrial monitoring program. Pre-implementation, Merrill WWTP faced high zinc levels in sludge, plant upsets, exceed phosphorous levels, yellow plant, failed W.E.T. tests, and failed proposed zinc limits. After initial grab site sampling and contacting of industries, samplers were added until now the program is utilizing a total of five samplers. Due to the industrial monitoring program, many of the problems identified prior to the monitoring program were traced down, better working relations with industries were developed, better operation of the plant, no zinc limits in permit, and zinc levels have decreased.
After the business meeting, lunch was served, followed by a raffle of donated items. Despite some suspicious shenanigans by the Steering Committee's table (they all won prizes pretty handily...), we were happy to give away one of our B&M fish/nature hat.
In my humble opinion, the most exciting speaker of the day was Josh Gruber, B&M Technical Services. Yep, despite coming down with a terrible cold (which has led to him losing his voice as of now), he gave a great presentation overviewing lift station controls and integration. Level sensing options were discussed, including floats, bubblers, submersible transducers, ultrasonic sensors, and level probes. It is important to properly size submersible transducers and the importance of utilizing the full resolution of the 4-20 mA signal was demonstrated. Separate from primary level controls, it is important to provide appropriate redundancy in lift stations.
We were especially grateful that Pat Stanford, Rochem Membrane Systems, came all the way from California to give a great presentation on reverse osmosis for wastewater separation. Reverse osmosis is a separation process, not filtration. RO membranes are used for this, and the layers were described. When implementing a system, bench tests are often ran prior to full implementation to ensure desired results are achievable. Reverse osmosis systems are largely used as landfill leachate treatment when leachate is inhibiting UV treatment.
Troy Larson, Strand Associates, concluded the presentations by going over Merrill’s biological phosphorus pilot. After a brief facility overview, he discussed the biological phosphorous removal (BPR) pilot. Initially a bench BPR study was performed. The results of the bench study provided both positives (good results, nitrification not required, cost recovery opportunities, strong staff support) and negatives (not exceptional results, nitrification occurs naturally in summer) to consider before moving on to the full scale BPR study. The positives outweighed the negatives, and a full scale BPR study is being conducted currently. While it's too soon to see the outcomes, we're (and many others, I'm sure) are looking forward to the results of this study.
Thanks to Terry and the Merrill WWTP staff for a great day!