Put Water to Work?

A New Jersey operator sees significant energy-saving potential in hydro turbines to capture the energy of flowing influent and effluent

Some 35 million gallons of wastewater flow daily into the Rahway Valley Sewerage Authority (RVSA) treatment plant, and a like volume of effluent flows out, all under the power of gravity.

Andy Sasso wondered: Why not put the energy of that water to work, producing electricity and saving money? Four years ago, Sasso, a shift supervisor at the plant in Rahway, N.J., took an interest in hydro turbines and their potential application in wastewater treatment plants.

Since then, he has been researching the technology, and would like to see treatment agencies around the country give it a closer look. He even went so far as to publish an article about hydro turbines in a 2007 issue of New Jersey EFFLUENTS, a publication of the New Jersey Water Environment Association.

Sasso, a 27-year veteran of RVSA, talked about the green power potential of hydro turbines in a recent interview with Treatment Plant Operator.

TPO:

What triggered your interest in hydro turbines?

Sasso:

Turbines caught my eye in 2005. Around that time there was a big push for green power. Hydro turbines are an old concept. The first ones were water wheels. Water turbines have been used from generation to generation. It’s a proven technology. I thought a little out of the box and decided you could place turbines in treatment plants and utilize the free energy of flowing water.

I started doing some technical investigation and breaking down the turbines that were available. Some great designs are out there that could utilize your head and velocity flows. You can arrange turbines according to the types that best suit your plant and your need for a supply of power.

With certain electronic components and controls, you can configure them to operate at 50 Hz or 60 Hz. You could incorporate them very quickly and easily, and also connect them to the utility grid.

TPO:

What do you see as the advantages of this technology?

Sasso:

You can place hydro turbines in any water source that has an intake and a discharge. They are environmentally safe, with no emissions. There is no cost to run them, as long as the water flow is constant. You have no worries about rising fuel costs.

They’re safe in that there is no danger of anything exploding because of a bad fuel mixture. They’re very easy to operate, and they basically maintain themselves.

There’s no reliance on fossil fuels and there are no emissions whatsoever. And you can place them online quickly to meet rapid increases in electric demand and fulfill emergency energy needs.

TPO:

What does the basic design of a hydro turbine look like?

Sasso:

A basic hydro turbine has a stator, rotor, shaft, wicket gate, and the turbine blades to capture the energy of flowing water.

You could actually retrofit water turbines into your inflow and outflow channels. You could build submersible channels that would create the velocity and the head needed to drive the turbine. A submersible turbine would be placed in a channel at a lower depth than the incoming wastewater supply. As it cascades down, you use that fall, that head pressure, to spin the turbines.

TPO:

What would a treatment plant do with the power generated by a small hydro turbine?

Sasso:

The easiest way to harness the energy is to connect a hydro turbine to your power grid using an induction generator. This generator automatically synchronizes to the grid, both phase and voltage. It will feed all generated power back to the grid.

TPO:

How did you go about researching the technology?

Sasso:

I worked on it for about two years. I did a lot of the research on the Internet, and I got hold of a number of technical books. I also spoke with an engineer — Gary St. Onge of St. Onge Environmental Engineering in Amsterdam, N.Y. — who is heavily involved in water turbines.

I picked his brain a little bit, and I really dove into the topic. I just kept exploring turbines and realized there are a great number of them on the market for whatever a given plant really needs. There’s a vast amount of information available, and if treatment plants would just look into it, they would find they can utilize this technology.

TPO:

What would be the most logical places to install hydro turbines in a treatment plant?

Sasso:

The most logical places are the headworks and the outfall. At our plant, for example, we have effluent screw pumps that release the effluent to a cascading waterfall. But the technology could apply anywhere you can get a cascading flow, or a channel where you can install a submersible turbine.

TPO:

What is your understanding about the payback on an investment in hydro turbines?

Sasso:

The payback depends on the size of the unit, the volume, the velocity of flow, and other factors. Typically, you can recoup your investment in five to eight years.

TPO:

What role does renewable energy play in your own treatment plant?

Sasso:

We have built a cogeneration facility using a blend of 70 percent natural gas and 30 percent digester methane. We have four Caterpillar engine-generators with 1,500 kW capacity. Right now, we are capturing the heat from the engines to dry our dewatered biosolids and heat our plant in a water loop.

TPO:

How do hydro turbines fit in with other forms of green energy being deployed in treatment facilities?

Sasso:

By using hydro turbines with wind turbines and solar panels, you could supply 90 percent of your plant’s needs from free energy. My whole concept is that it would be great to be the first totally green treatment plant.

The technology is out there. I believe hydro turbines are going to be the next big thing in green power in the next five years. The energy source is right there in front of us. If we can utilize it, it’s there for the grabbing. It’s free, and it’s waiting to be harnessed.



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