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(written in 1999) Public comment about wastewater treatment operations is usually non-existent, unless it is negative. Usually, when the phone rings or the newspaper writes a story about the local wastewater treatment facility it has to do with the need to increase sewer rates, improve outdated facilities, the practice of sludge application, or the need for odor control. One Northwest Iowa Wastewater Treatment Plant has been the feature of much positive press and frequent "pats on the back" by local citizens because of the odor reduction they achieved. Le Mars, Iowa, a growing community of about 10,000 people has had a long-standing and ever-worsening odor problem. Much of the odors are a result of the heavy BOD loading that must be treated. With influent CBOD loadings that average over 8,000 lb/d and sometimes peak to as high as 60,000 lb/d odor has been the "talk of the town". Until recently the talk wasn’t positive. With businesses, residential areas, and a Little League complex within a few hundred feet of the wastewater plant, there were plenty of complaints. Neighbors often complained that they had to keep their windows closed and run their air conditioner because the odor was "unbearable" to many of them. Comments such as, "We tried to grill out on the patio last night, but we couldn’t stand it and had to go inside" and, "The odors are driving me crazy", as well as many others were commonly heard around town. Terry Branstad, Governor of Iowa in 1994, had proclaimed Le Mars as the "Ice Cream Capitol of the World". Le Mars is the home of the largest family owned ice cream maker in the world. The wastewater treatment plant was originally constructed in 1958. On the average since that time, the city has had to do a major expansion/upgrade every 7 years to accommodate the increasing loadings. The plant consists of preliminary treatment, flow equalization, primary treatment, 2 deep Roughing Filters with plastic media, two Trickling Filters, and a complete-mix activated sludge plant. Over 8 million gallons of raw sludge is treated in an anaerobic digester and then thickened to about 4% TS before it is land applied year around. With the plant in the news so often, citizens often wondered why the odor issue was not a priority. A lot of dollars had been spent, but the odors grew more frequent and less bearable. The plant Superintendent wanted to find a solution to the problem and turn the public perception around. "It just didn’t seem right to be called the "Ice Cream Capitol of the World" and have lingering, often very strong odor hanging over the community. Citizens expected better and so we set out to find the answer", said the Superintendent. First, he established a volunteer citizen task force made up of neighbors, City officials, and interested persons to assist the City in evaluating various products. Those trials have included chemical addition, process control improvements, a 1997 plant upgrade, and products from Odor Control Company (www.odorcontrolco.com). The primary job of the task force was to monitor and record odor events (or the lack of). While the task force was helpful, over time the people seem to lose interest. West Central Environmental Consultants (WCEC) from Morris, Minnesota was hired to conduct a detailed "odor study" and develop specific recommendations for a long-term solution. WCEC analyzed a number of air and water samples and soon issued a detailed report that identified the sources of the odors and the levels of Hydrogen Sulfide at each source. While it was found that the odor was being released from nearly every plant process, the Roughing Filter, Primary Clarifiers, and Trickling Filters were identified as those with the highest intensity. WCEC went on to make a public report to the City Council recommending that a Biofilter be installed to handle the Roughing Filter odors, and that Biocovers be installed over the two Primary Clarifiers. Estimated equipment and construction cost was $95,000. The City Council approved the recommendation and authorized the expenditure. However, with another major plant upgrade also in the works, the City Administrator wanted to first see what impact the improvements would have, without adding the Biofilter or Biocovers. It had now been some three years and there had been many local news stories published about the pant upgrade. Citizens wondered out loud why with all the money that had been spent, were there still terrible odors? The City’s design engineers, McClure Engineering Company of Fort Dodge, Iowa (www.mecresults.com) was asked to review the WCEC recommendation and do further analysis. While the plant upgrade may have helped slightly, it was not nearly enough. McClure suggested a number of operational modifications, such as increase trickling filter recirculation, increased sludge withdrawal from the clarifiers, and frequent flooding/flushing of the Roughing Filter. The operational changes were made and again there was improvement. But again, it was not enough. It looked like the Biofilter (or an air scrubber) was the only option. Estimated capital expenditure for these improvements had grown and now stood at between $100,000-$200,000. The City was prepared to spend the money. In the spring of 1998, Mike Trotter of McClure Engineering suggested the City try one or two more things before proceeding with the project. He had received some information on a couple of products and he felt the City should evaluate them. The products included some "odor sleeves and granules" (www.odorcontrolco.com) which uses the ‘essential oils technology". Reluctantly, the plant Superintendent agreed to purchase a small quantity to see what happened. He felt that this was nothing more than a "snake oil" and that it wouldn’t work. The product comes in 25 lb pails and looks something like kitty litter with a strong fragrance. The product is poured into a three-foot long cloth sleeve and simply hung between the odor sources and the public. The sleeves are placed every 8-10 feet along the perimeter of the plant. The granules last for 3 months and them must be replaced with fresh granules. It seemed to help, so the Superintendent ordered enough to do about 800 feet of his fence. The sleeves were also hung inside the Roughing Filter (which is covered by a dome) and in the screenings dumpster. Citizen input was again solicited by using press releases in the local paper. It is interesting to note that since the sleeves had been hung, the few complaints received came during a time when the Roughing Filter was being flooded or sludge was being land applied. The local paper did yet another story, this time on the "odor sleeves". Again, the phone began to ring; however the calls and the public comments were all positive! One man, who has lived next to the WWTP for many years, stated that he sort of "forgot about the smell that summer". It wasn’t until he read the newspaper article that he realized there had been no odor all summer. Following this, liquid products from the same company (www.odorcontrolco.com) were ordered and now are routinely "misted" into the atmosphere. The liquid products are diluted 150:1 or more. The WWTP Superintendent and many others have noticed a significant reduction in odors. Within minutes of starting the misters, the odors were gone. This is not to say that there are never any odors, but they are now very manageable. By simply monitoring the odors inside the plant and adjusting the dosage of the liquid products, the odors are controllable for Le Mars. Annual cost for the products used in this community are lower than the operations and maintenance costs would have been for the scrubber or Biofilters, and there was no capital expense. "How do we know it is working?" says the Superintendent, "because people tell us it is. I often have gotten comments from a variety of folks and they have been quite positive". Not only has the story made the local paper and radio station, it was a feature of a regional television newscast and in a regional newspaper. Citizen complaints have now become citizen compliments thanks to the low cost products from Odor Control Company, Inc. Le Mars has also used Biomodifiers from the same company to control grease and grease pit/lift station odors. Many communities have followed suit and begun to use the Biomodifiers for control of lift station grease, lagoon sludge, and now for BOD reduction in wastewater lagoons. It works! Mark Simms served as the WWTP Superintendent in Le Mars from 1993-2002 and he can be emailed at: simms@lemarscomm.net for further information regarding this typical success story. He now owns and operates Management and Operational Resources, a Water/Wastewater consulting, training, and contract operations company that recommends several of OCC's products. |
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