Tailor Made

Operators and engineers in Rock Falls worked together to create a new tertiary treatment plant that’s efficient, effective, safe, and ready to grow
Tailor Made

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Walk around the new Rock Falls (Ill.) Water Reclamation Facility and you can see and feel that it’s different.

Skylights and windows brighten the buildings. Ample stairways connect levels instead of ladders or narrow metal steps. Pumps are mounted away from the walls to allow easy servicing. There are no confined spaces anywhere. The laboratory is spacious; influent and final effluent samples are piped right in.

There’s a lunch and break room with space outside for a picnic table. There’s a shower, and a washer and dryer for team members’ uniforms. Each building has a restroom. Everything from the headworks to the outfall is set up for operators’ convenience, efficiency, comfort and safety.

Brilliant engineering? Yes — the kind you get when consultants and operators collaborate from even before the first lines are drawn on a plan. Plant superintendent Edward Cox and his team worked with project engineer Bob Gasper of the Willett Hofmann & Associates engineering firm of Dixon, Ill., from 2003 until the plant was commissioned in July 2011.

The result is a $20 million, 3 mgd (design) tertiary facility that consistently meets its discharge permit, operates efficiently, makes operators feel at home and — perhaps best of all — came in on budget.

“Willett Hofmann had been the city engineers for years,” says Cox. “They went into the project with the same attitude we did — that we were going to work together. Other firms that approached us basically gave us the cookie cutter. We didn’t want to get stuck in that mode. Almost every piece of equipment in this plant was hand-picked.”

 

Tougher standards

The plant project began in 2003, the same year Cox joined the city. The old treatment plant was built in 1935 and expanded three times, most recently in the 1980s. Ultimately, its packed biological reactors (PBRs), essentially trickling filters with plastic media, could not meet new ammonia and phosphorus permit limits.

“The new ammonia limit was 1.5 mg/L, and we could only reach that in the hot summer months,” recalls Cox. “The PBRs couldn’t retain heat, and we couldn’t get the nitrifiers to work correctly in colder weather. We would violate right up to the heat of summer in late June or early July, and then in September, when the nights got cooler, we’d fall out of compliance again.”

The plant site would not accommodate expansion: It was across the street from the high school and hemmed in by the Rock River and residential neighborhoods.

In 2003, the city and engineers chose a 19-acre site for a new plant on farmland about 1.5 miles west of the old one.

Formal design began in 2007, and transfer of flow to the new plant began in July 2011. A pump station at the old plant, with a Muffin Monster grinder (JWC Environmental) and four Smith & Loveless dry-pit pumps rated at 1,500 gpm, delivers wastewater (average daily flow about 1.5 mgd) to the new site through a 20-inch ductile iron force main.

The wet well at the new plant is set deep enough to allow gravity flow from future residential and industrial development in the area. Spaans Babcock screw pumps lift the flow to the influent building. At the headworks, a Parkson step screen captures material, compacts and dewaters it and delivers it to a dump container. A Eutek (Hydro International) system collects, classifies and dewaters grit, and a Eutek Grit Snail unit conveys it to a container.

 

Nutrient removal

The wastewater passes through a Parshall flume for flow measurement and is lifted to the three-channel Envirex oxidation ditch (Siemens Water Technologies) by a second set of Spaans Babcock screw pumps.

The oxidation ditch provides secondary treatment with biological nutrient removal. Exiting that process, the water passes through a splitter vault and enters the two 90-foot-diameter Envirex clarifiers. The splitter vault provides capability to add ferric chloride for phosphorus removal if necessary.

From there the flow proceeds to tertiary treatment in three basins with AquaDisk cloth disc filters (Aqua-Aerobic Systems), through UV disinfection (TrojanUV), and through final flow metering before discharge to the Rock River.

On the solids side, telescoping valves in the clarifier sumps draw off activated sludge. Flygt pumps (Xylem) send return activated sludge (RAS) back to the oxidation ditch, and waste activated sludge (WAS) to the aerobic digesters feed air with Kaeser blowers and Sanitaire fine-bubble diffusers (Xylem). The plant SCADA system adjusts airflow to the digesters based on sludge levels in four basins. Digested biosolids are dewatered on a belt filter press (BDP Industries) and hauled to landfill.

 

Making choices

Credit for the plant’s successful first year and bright future belongs to careful planning and design. The first key objective was to pick a location that allowed room for expansion over 50 years or longer.

“We’re not landlocked now,” says Cox. “Everything is already in place in case we have to expand in the future. We could mirror this plant in a heartbeat — we’d just flip the design and build another right beside it. Everything is all ready to be connected.”

The second key objective was ease of operation and maintenance, and here Cox and assistant plant superintendent Steve Mulvaney worked closely with Gasper.

Before joining Rock Falls, Cox had worked 10 years with a private water operations and management company. “I had worked at different sites all over and had seen what worked and what didn’t,” he says. “I had certain things I wanted as an operator. I wanted an Envirex ditch, and I wanted Envirex clarifiers. They’re widely used, there’s a lot of experience with them, and it’s easy to get parts.”

Cox and Gasper traveled extensively to look at equipment such as bar screens, grit systems and biosolids dewatering presses. They looked at SCADA systems at several plants in Illinois before choosing to work with SCADAware of Bloomington, which had provided the system for the Rock Falls water department.

“The water side was very happy with their services,” says Gasper. “We laid out what we wanted, and we came to the conclusion that there were advantages to using the same provider for both sides of the city system.” Among the system’s features, manuals for all plant equipment are built in and accessible on-screen.

 

Little things matter

Cox and Mulvaney also collaborated with Gasper on multiple details of the plant structures and workspaces. At times they sought input from operations and maintenance team members Allan Briggs, Dan Reinhardt and Scott Breed.

“My philosophy is that I’m not designing it for myself,” says Gasper. “If a piece of equipment gets installed that the team didn’t like from the very beginning, it’s just human nature that they’re going to complain about it and they’re not going to want to use it. But if they really like what is put in place, they’re going to work with it and they’re going to take care of it better. So let’s deal with the concerns up front in the design, so that everybody is on board and we deliver a great product.”

Cox adds, “We tried to make this an operator’s plant — make it simple to operate and easy to maintain while getting rid of all the headaches like confined spaces, low ceilings, and really hot environments in the summer.

“There are no confined spaces. In every basement you could fit multiple people. We have positive ventilation. The ceilings are 10 feet high. Every staircase is four feet wide with large landings. Another key item was access for maintenance and service. There are no pumps against the walls. We can actually put a person on each side of the pump and they can move their elbows without cutting them up.”

At one point during design, city staff pointed out that there was no easy way to remove the RAS and WAS pumps from their basement location for replacement or service. In response, the engineers provided a removable grating in the floor above through which the pumps can be lifted out using a portable hoist.

Mulvaney observes, “Maintenance is easy to do here. Things are placed where you can get to them. You don’t have to climb over pipes or crawl through a tunnel to grease something. Everything is right there in front of you. It’s a matter of just walking up to any piece of equipment to check or change the oil or adjust belt tension.”

 

Ample amenities

Mulvaney had great flexibility to design the laboratory. “I sat down with the architect and was told, ‘This is how big your space is — what do you want to do in here?’” he recalls. “It was nice to be able to set it up with a certain workflow in mind.

“We have two U-shaped work areas, each with a center island. There are separate areas to keep operations testing away from DMR [discharge monitoring report] testing. Sinks are located where they’re functional for us. There are separate writing areas for doing reports. Three or four people can work without bumping into each other.”

Refrigerated samplers for influent and final effluent are inside the lab. A wall-mounted still saves countertop space. There are plenty of storage cabinets, closets and sinks. Windows and skylights make the atmosphere pleasant.

 

Flexible at every step

The Rock Falls team even had input on architectural details. “Bob and I went to Rockford (Ill.) and actually picked out the brick,” Cox says. “Steve and I picked out the color of the metal roof. Every place that’s painted, we chose the colors — even for the piping, which is all color-coded.

“We picked out the floor tile color and pattern. Our painted floors have a Tnemec coating that’s used in auto repair shops. We can walk in with our boots icy and wet, but once you step on that floor, you don’t slip.” (The coating includes 3 mils of Series N69 Hi-Build Epoxoline II and 6-12 mils of Series 281 Tneme-Glaze.)

Collaboration continued during two years of construction. “Steve and I were out there often, and changes were made as we went,” says Cox. “We had many meetings. We even discussed exactly where the road should go. Now we have a big circle drive so any delivery vehicle can pull in and pull right out.”

In the solids building, the belt filter press discharges from a conveyor directly into a dump truck or roll-off container. The vehicle maintenance building includes a truck wash bay and a large shop area with four bays.

A variety of small changes were made on the fly. Gasper observes, “If we were running piping in a building or placing hose bibs for washdown areas, they might ask, ‘Can we just move that over here?’ Doing so might not even change the cost, but yet it might help them in the long run. They took ownership of the construction process to see that everything was going to be in the best location.”

 

The way forward

Looking back, Cox is grateful to have worked with engineers who listen: “As operators, we work with these systems every day. We know the good and we know the bad. We may not be able to tell you how to build a structure, but we can tell you how the plant is going to run once you build it.

“I think you’ll see more of this working together in the future. Operators now are much more educated than they were 20 or 30 years ago. We’re starting to see younger people coming in who have gone to school, have worked with engineers, and may have some engineering background of their own.

“At the end of the day, when operators can talk back and forth with the engineers, and both sides can be flexible, it makes a world of difference.”



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