North Liberty, IA

Membrane Bioreactor Wastewater Treatment Plant: Phase I

  • Client City of North Liberty
  • Type Wastewater
  • Services Treatment
  • Construction Cost $8.5 Million
  • Project Manager Steve Troyer, P.E., BCEE
  • Project Engineer Matt Kasper, P.E.

Challenge

Growth brings challenges along with opportunities for innovation and sound environmental choices. North Liberty is a rapidly growing community in Johnson County, near Iowa City. This growth required expansion of the existing wastewater treatment facility, originally constructed in 1998. In addition to community growth, the sensitive nature of the receiving stream, Muddy Creek, which flows through residential neighborhoods and near elementary and junior high schools, made an advanced treatment technology desirable.

Before moving ahead, the city and their consultants met with IDNR to get buy-in for this new MBR process.   The agency was supportive of the project and upon completion recommended it for the Iowa Governor’s Environmental Excellence Award:  “I would like to nominate the City of North Liberty and their consulting engineers, FOX Engineering Associates, Inc., for the excellent work they did on the City’s new wastewater treatment facility.  Steve Troyer with FOX Engineering did most of the technical design for the new plant.  North Liberty constructed one of the newest technologies, Membrane Bio-Reactor process, for their wastewater treatment. This is the first such facility in the State of Iowa and third in the Mid-west region.”

Environmental Engineer, IDNR WES

Membrane fibers

Membrane fibers

Solution

Completed in March of 2006, a Facility Plan evaluated a number of options, considering both up-front capital and life-cycle costs, and other non-economic considerations, such as reliability, flexibility, and ease of operation. With a great deal of input from city staff, FOX recommended converting the existing sequencing batch reactor activated sludge plant to a membrane bioreactor (MBR) process. The MBR is an advanced form of activated sludge that utilizes membranes to produce a very high quality effluent – which pleased the ecologically responsible city. The advanced treatment technology also allowed more flexibility in meeting future, more stringent regulations. The facility plan also evaluated funding options for the project, which was eventually funded through the State Revolving Fund (SRF) program.

The most significant feature of this project is the application of the membrane bioreactor (MBR). MBR technology has been around for many years, but in terms of wastewater treatment technology, it is relatively new. North Liberty wanted to utilize an advanced treatment process to minimize their impact on and help improve the water quality of Muddy Creek. FOX Engineering suggested an MBR, which is one of the most advanced wastewater treatment technologies available.

Although there are several installations throughout the country, this technology had never been utilized on a municipal plant in Iowa. This plant is the first of its kind in Iowa. Critical to the success of the project was getting buy-in from the community, school district, environmental groups, and IDNR.

Cylindrical rotary drum fine screens

Cylindrical rotary drum fine screens

Outcome

Achieving disinfection limits without use of chemicals or a UV system reduces operating costs. While most permits only require disinfection during certain months of the year, the MBR provides year-round disinfection without added cost. Simplified operations and improved process reliability help ensure consistent, high quality effluent at all times.

The reduced footprint size of the plant allows for future expansion of the plant without the need to consume more land.  All of these benefits provide social and economic value to the community beyond conventional systems.

North Liberty and FOX Engineering have demonstrated that the MBR process is a viable technology for Iowa. While it can be more expensive than conventional methods, it provides a higher level of treatment and produces a consistent, high quality effluent. The design, construction, and operational knowledge gained can be shared with other communities wanting to implement this technology. For communities desiring a higher level of treatment, this is certainly an option. This technology can help them attain their goals of returning their streams and rivers to the desired pristine state – the right thing to do.

Mixed liquor return pumps

Mixed liquor return pumps

Recognition

FOX Engineering Associates, Inc. and the city of North Liberty received the American Council of Engineering Companies (ACEC) Grand Conceptor (1st Place over all categories) and First Place Award for Engineering Excellence in the Water and Wastewater Category for the 2010 Membrane Bioreactor Wastewater Treatment Plant. The project also received the Iowa Governor’s Environmental Excellence Award for Water Quality in July 2009, recognizing leadership and innovation in the protection of Iowa’s natural resources.

Permeate pumps

Permeate pumps

 

 

Aeration basins

Aeration basins

A FIRST!!  Although there are several installations throughout the country, this technology had never been utilized on a full-scale municipal plant in Iowa. Implementing this process in North Liberty required blazing a new trail.

While conventional treatment technologies are adequate for many situations, sometimes “out-of-the-box” thinking is required to advance to a higher level. North Liberty wanted to go the extra mile and not just meet permit limits, but actually improve the water quality in Muddy Creek.  FOX provided the engineering expertise to get there.

Imagine consistently producing 0.02 ntu water (the drinking water turbidity standard is 0.3 ntu) with little or no bacteria and viruses, without the use of disinfection, from a wastewater plant!

North Liberty’s MBR facility has been doing that for years.