Industrial Utility Efficiency    

Brown and Caldwell: Tackling Wastewater Aeration Challenges

Blower & Vacuum Best Practices interviewed Henryk Melcer, Senior Process Engineer, Vice President, at Brown and Caldwell.

 

     
Henryk MelcerHenryk Melcer, Senior Process Engineer, Vice President at Brown and Caldwell.
   

Good afternoon! Tell us about your background in water quality and wastewater treatment.

I’m senior process engineer with Brown and Caldwell. I work in the firm’s Seattle office and lead a group of 9-10 process engineers doing work throughout the Northwestern United States. I’ve been with the company since 1994.

I began my career in the industry in 1976 when I served as project engineer at AWARE, Dr. Wesley Eckenfelder’s water resources engineering firm in Tennessee. I took on my dream job in 1980 as head of Biological Process Development at the Wastewater Technology Centre (WTC), Environment Canada. WTC was a federal government research laboratory dedicated to advancing technological solutions designed to address environmental challenges. It was recognized as one of the three top wastewater research laboratories in the world. WTC provided state of the art engineering knowledge and process data to enable industry to build systems that would comply with the federal water quality regulations.

I’ve also had the pleasure of serving on the ASCE-EPA technical committee that helped develop the Environmental Protection Agency’s design manual for fine pore aeration systems. It was a great experience and I learned a lot from very well recognized people on that committee. I supervised two full-scale aeration demonstration facilities in the Midwest: in Monroe, Wisconsin, and Frankenmuth, Michigan. This was to demonstrate fine pore aeration and the newly developed (at that time) off-gas measurement of oxygen transfer efficiency.

I’m originally from England. While attending the University of Birmingham in Birmingham, England, I earned a Bachelor’s degree in Chemical Engineering, followed by a Master’s and Doctorate degrees in Chemical Engineering.

 

Please describe Brown and Caldwell and the services it offers.

We’re an employee-owned environmental firm offering a comprehensive range of engineering, scientific, consulting and construction services. Our expertise is in the design of progressive solutions that help municipal, federal and private organizations overcome some of their most complex environmental challenges.

We’re headquartered in Denver, Colorado. In all, we have more than 1,700 professionals working in nearly 50 locations, primarily in mainland USA. About 45% of our work is focused on wastewater engineering now, having made a conscious effort to diversify into water treatment and industrial wastewater treatment. That was after we absorbed Dr. Eckenfelder’s old company, which is ironic because it came full circle for me. We also carry out environmental impact assessments, water resources modeling, collection system and stormwater modeling, and a range of other services.

 

What are the most common challenges with aeration blower systems at wastewater plants today?

It’s in my interest as a process engineer to make sure I get what I want in the control of oxygen gradients in aeration basins, so over the last two to three years, I’ve become pretty heavily involved in aeration control systems and how they work. The need to control the rate of oxygen added to the aeration system has become particularly acute with the increasing application of nutrient control systems. In order to save energy, we’re using processes such as simultaneous nitrification-denitrification (SND), short-cut nitrogen control and Anammox®. Plants are continuing to move from providing for Biochemical Oxygen Demand (BOD) removal only to nutrient removal processes.

A lot of people are struggling to figure out how to make SND work at low Dissolved Oxygen (DO) concentrations of 0.1 to 0.5 milligrams per liter (mg/L). It’s not easy to do. Sometimes, it gets difficult to make the connection between the different players in aeration control: software programmers who put together the control algorithms, control engineers, systems integrators and process engineers.

 

Does nutrient removal put more air demand on blowers versus BOD removal?

Definitely. When you nitrify one needs to supply approximately four-and-a-half parts of oxygen per one part of ammonia, compared to one part of oxygen per part of BOD. Allowing for the different concentrations of BOD and ammonia, the air demand increases by a factor of about two.  As a result, a plant could end up doubling the number of blowers needed. More air, of course, equates to more energy cost.

This means treatment plants might be looking at significant additional expenses when they upgrade to nutrient removal. This also drives the need for many plants to find more efficient blowers to replace older models when they upgrade.

There are other ways of reducing overall demand for oxygen but there is still a very significant increase in the amount of air that needs to be delivered by the blower systems. 

Aeration Blower

Aeration blowers continue to play an important role in helping treatment plants achieve energy savings. 

 

Given these changes, what have you observed as far as aeration control strategies?

The provision of air in response to the oxygen demand in wastewater aeration systems varies diurnally and seasonally. This is a non-linear process and, therefore, a Proportional Integral Derivative (PID) control algorithm is not the best way of accommodating this need. 

Instead, plants should be using floating control, which is a flexible algorithm that essentially monitors the aeration process and determines if a correction is needed and then makes the correction. This allows the blowers to ramp up more slowly and adapt to the process, which, in turn, minimizes power draw and saves on energy costs.

This gets back to programmers, control engineers, systems integrators and process engineers working closely together to determine the best method of control for the blowers.

 

Are there other types of aeration control strategies showing success?

There are a number of successful strategies and they’re all geared toward saving energy. These include ammonia sensor-based controls, ammonia versus nitrate (AVN) control, and Most Open Valve (MOV) control, among others.

Energy savings is the driving force behind all of these methods. Of course, nearly everyone looking to save energy first looks at the blowers themselves. And even though the system control strategies give you more energy savings than blowers do, treatment plants will continue to look at blowers to achieve savings.

I must admit there’s been a lot of interest in using high-speed blowers because they’re perceived to be a lot more efficient and therefore people can save energy, although there’s still a huge category of folks who like the old Turblex type of blowers. There were a few stutter steps in introducing high-speed blowers. Overall, I think high-speed blower technology has become a lot more reliable and is delivering on the goods with respect to efficiencies and providing energy savings.

So yes, there are several ways one can manipulate the manner in which you control the airflow rate to the aeration basin. It’s important to consider changes in oxygen uptake rate along the length of the basin. That means an algorithm is required to control the amount of air supplied to each aeration zone along the length of the basin.

 Air supplie pipes

An algorithm is required to control the amount of air supplied to each aeration zone along the length of the basin.

 

What is your view of new processes, like Anammox and their impacts on air demand?

I wish I were 30 years younger because Anammox is the biggest breakthrough in the industry in the last 25 years.

There’s an organism that works in concert with ammonia oxidizing bacteria. In a reactor with alternating on-off aeration, when the air is on, the ammonia oxidizing bacteria will oxidize ammonia to nitrite. With the air off the Anammox bacteria are activated and convert the ammonia and the nitrite directly to nitrogen gas, which eliminates the need for carbon. About 40% of aeration demand is also eliminated.

Anammox is a new technology that’s only been implemented within about the last two or three years. It’s going to catch on quickly because of the savings it offers in capital and operational costs since it uses less air.

 

What other trends will impact the industry in the next five years and beyond?

The EPA is going to continue to roll out its mandate for ammonia removal across the country as various regions establish the scientific basis for implementing nutrient controls. I think that, as more EPA regions complete their Total Maximum Daily Loads (TMDLs) investigations, they will have the scientific basis for implementing nutrient controls, and we’re going to be faced with more and more plant upgrades to nutrient removal. I imagine it’s going to go on for the next five to ten years; requiring extensive expansion in aeration basin capacity.

I also think the complexity of treatment processes that will be implemented will be more challenging. For example, SND works very well in some cases but it’s not very well understood. If regulatory authorities induce the adoption of more of these types of processes on the industry, there will be increasing pressure on control systems to ensure compliance, while achieving process reliability. And blower systems are clearly linked to this need.

Of course, there is also the challenge posed by the increasing shortage of engineers in this field in the coming years since it’s well known that half of the professionals in this industry will be retiring in the next 10 years. It’s a major concern.

 

Would you encourage young engineers to get into the field of water resource recovery?

I would, especially since it offers a significant opportunity for a rewarding career in many regards. I’ve got to believe some folks have an interest in contributing to an improved environment and to the public good by harnessing the newer and emerging technologies. We mentioned Anammox; there is other emerging technology that is pretty interesting and revolutionary that will make our systems more reliable, more efficient, and improve the quality of effluent discharge and certainly the quality of water we drink.

 

Thank you for sharing your insights.

 

For more information, please contact Henryk Melcer, email: hmelcer@brwncald.com, tel: 206-749-2219, or visit www.brownandcaldwell.com.

To read similar Aeration Blower System Assessment articles, visit https://www.blowervacuumbestpractices.com/system-assessments/blower-systems.