Why should a wastewater treatment plant always have to look like, well, a wastewater treatment plant? A visual trip through project files of Aqueonics Inc., based in Greenville, SC, reveals photos of what look like houses in a variety of settings. But a look inside these “homes” would reveal a wastewater treatment system surprisingly versatile in what it can do. Besides giving developers a system independent of the regional or municipal wastewater systems, which might already be at peak capacity, the 30-year old company also believes firmly in the idea that wastewater holds the key to a growing number of issues when it comes to water conservation.
The typical Aqueonics system treats approximately 100,000 gallons per day of wastewater effluent. This equates to about 330-340 market-rated houses. The footprint for such a system is roughly 40 feet by 100 feet, or a typical house lot for one housing development’s treatment plant. For a 30,000-gallon facility, the footprint involved will be roughly that of a typical starter home, approximately 30 feet by 30 feet, according to Jerry Trayham, owner of Aqueonics.
“We embed that ‘house’ within 50 feet of an inhabited residence because there is no odor or noise,” says Trayham. “A benefit to the developer is that their need for installing a waste treatment system doesn’t impact their landmass because the footprint is so small. The only thing you have to determine is how you are going to discharge your water: either by subsurface beds or through a nearby water user.
“If subsurface discharge is the method you use, the soil permeability is a major issue—it must at least have the ability to absorb one gallon per square foot per day. Therefore a 30,000 gpd facility with only marginal soils would require a discharge bed size of 100 feet by 200 feet.” But a discharge bed in that facility could also be a recreational facility, with ball fields, golf courses or putting greens.
How can a wastewater treatment plant embedded into a neighborhood not use much landmass and be environmentally friendly and user-friendly all at the same time? The systems that Aqueonics builds do all of the above, says Trayham, but there is also a much more basic reason for these downsized treatment plants.
Wastewater enters the building by way of gravity or a lifting system.
“The primary reason for the wastewater treatment building is you’ve got to control the process environmental conditions to make it work properly,” says Trayham. “This is where other companies experience problems in their quest for doing 24-7 quality effluent reduction of nitrogen, nitrates and other components.
“In 1979 our scientists figured out that the only way you can successfully control the environmental conditions is to put the process in an environmentally protected area. We match the buildings to the area because we can put it within 50 feet of an inhabited residence without any odor or noise, but the real reason for the building is to control environmental conditions of the process.”
Wastewater enters the building from the community or small industry, by way of either gravity or a lifting system. The flow comes in largest volumes during the hours when people are at home. For a commercial operation, the peak hours are typically just the opposite.
The process used for aquifer recharge, wastewater reuse, or wastewater mining is one that produces a high quality of effluent. It uses an alternating aerobic-anaerobic trickling filter system. The system is made up of three fiberglass interior aerobic towers and three anaerobic towers; conventional framing forms the exterior. Those towers are on the top level. Two floors below those are a series of tanks, pumps, and piping.
The first step is the pumping of the effluent into a headbox, from which it then flows into a primary clarifier; any remaining flow returns to the flow equalization for recovery and reuse of the system. If the pipe coming into the collection system of the plant is gravity-fed, that pipe will be from 8 to 12 inches in diameter. But if it’s a forced main, it will be a simple 2-inch pipe; this is the case in the Hampton Township project described below. The primary clarifier is a tank containing the pureed waste that gives a continuous consistent flow volume. From there it is pumped to the first aerobic tower, where the raw sewage is distributed across a fixed-film media.
The media in this first tower have a density of 32 cubic feet per square foot, set on a 60-degree plane through egg-crate style openings. What is happening is that the raw sewage is being distributed through spray nozzles on a given design pattern; every square inch of that media is contacted with the raw sewage. The bacteria contained in the raw sewage trickling down through the media—approximately 16 feet tall—cling to the media walls.
The buildings can be placed within 50 feet of an inhabited residence—and without any odor problems or noise.
Since these are heterotrophic bacteria, (as opposed to autotrophic, which can produce their own food), they digest the solids while anchored to the walls of the tank for support. After it trickles down into this media, the processed water is collected in a hopper. While in the anaerobic tank (the next one) it is also at 32 cubic feet per square foot of density, but it’s submerged.
At this site the bacteria are eating 10 times faster to reach the oxygen contained in the nitrogen component of the waste materials. At this point much of the waste product is starting to be lost, resulting in cleaner water. The effluent now pumps up again to tower two. The density of that medium has been increased to 42 square feet per cubic foot—a greater density and a larger colony area.
Also just before this point, the bacteria have mutated from to autotrophic. At this reaction point the ammonia nitrogen is stripped out. Both nitrogen reactions are able to safely release nitrogen gas into the atmosphere.
“This is a true de-nitrifying process because you are using variations of bacteria in alternating sequences so that one is stripping out levels of nitrate nitrogen and the other is stripping out levels of ammonia nitrogen,” says Trayham. “Those two combined make up the total nitrogen concentration. Therefore, when a company says they are de-nitrifiers, they can only be that if they are using variations of bacteria to achieve those end results; that’s one reason we have this triple alternating stage.”
By the time the liquid moves up again, this time to the third aerobic tower, that media has increased in density to 62 square feet per cubic foot of media. At this point there is almost 100% greater surface than was present in the first tower. There is also only 10% of the original amount of the material present in the process now for the bacteria to digest.
“What has happened is that you’ve taken this heavily laden bacterial solid component process from tower one to tower three,” says Trayham. “By the time you have reached that point, bacteria have eaten both other bacteria and the solids; the liquid is getting cleaner and cleaner.”
By the time the liquid trickles down into the third anoxic reactor, that water is clear, although it still contains a tremendous amount of bacteria. “Depending upon what limits you’re trying to meet with your effluent needs as far as permitting—golf course irrigation, aquifer recharge, public playgrounds, chill water service, DOT de-icing service or vehicle washing, whatever function you will be performing—that determines what water quality you’ll need out of the system,” he says.
“The water quality also determines how we will kill the remaining bacteria,” says Trayham. “Destruction of the final bacteria typically involves removal through an upflow sand filtration system with UV disinfection system.”
For swimming-pool-quality water, the limits acceptable for fecal coliform are less than 200 mg per liter of nitrogen. If the water needs to be drinking-water quality it needs to be less than 20 mg per liter of nitrogen. For water placed in a playground area, the water must be guaranteed to be drinking water quality; this can be done by monitoring the water continuously.
The size of the Aqueonics wastewater treatment facility determines whether or not there will be an onsite lab for monitoring or testing of the effluent. Any facility 150,000 gpd or greater requires an onsite lab, according to Trayham. Anything below this amount is required to have a licensed lab do all the testing and verifying. For conditions where the water is to be use in an application in which it must be clean, data can be captured and evaluated every 10 seconds or less if needed.
The original physical process used gamma radiation (as opposed to the UV radiation now used), to kill the bacteria in the final step. This was developed by a scientist in California. The patent was originally purchased by ARCO. Eventually the patent for the system shifted back to Aqueonics.
A typical system can treat 100,000 gallons per day.
The pumps that Aqueonics uses in its facilities include Hydromatic, Goulds, Peerless, Imperial, Zoeller, Ram Industries and F.E. Meyers, among others. “We use the different brands depending on the various processes involved as well the best cost-efficiency we can find,” says Trayham. “But we do make use of all of those vendors. We prefer them because of their high quality.”
Aqueonics uses Dura-Pac filters in its systems. Those are purchased through NSW Environmental Systems in Roanoke, VA. “Since we have a fixed-film media, our filters never have to be changed out either,” says Trayham. “As long as the operator continues to operate the facilities as they are supposed to be done, there is no reason for it to clog. PVC pipe will last for 50 years. We haven’t run into any problems. We do watch carefully the quality of the media, being sure it doesn’t delaminate. To date we’ve had no problems with delamination of the media. The media consists, typically, of plastic blocks 2 feet by 2 feet by 4 feet. The media—contained within the towers and reactors—is stacked up in a variety of patterns to achieve the biological colony.
“We have air systems included in our setups to ‘burp’ the media. As long as that is done on a continuous basis, that media will always stay clear and things will operate efficiently. There is an air system in which we puff air through the bottom to release the air in those cells so that, if there is anything starting to clog, it would open it back up and the bacteria would continue to function.
“This would only be an issue in tower number one because that is where the majority of the solids are. As things proceed through tower two and tower three the solids are highly reduced, becoming clean water.”
Onsite generators maintain power during any outages. Were there to be a leak in a tank, that tank would be drawn down and isolated while everything else continued to operate. The fluid itself at the third stage would be recycled back to the flow equalization tank after any repairs would be made and go through the process again. “In any case you are never letting anything out of the plant that would be less than what is required and acceptable by the permit,” says Trayham.
“The flow entering the system would never be stopped. Instead you would isolate the process at the flow equalization tank, which is 137% more than the full flow that is coming into the plant. A pumping truck or sludge hauler would be called and they would come in and pump out the flow equalization tank.”
One challenge that Aqueonics faces comes with the fact that developers and builders tend to complete housing developments in phases, sometimes taking over three years before the project is completely done. With the first phase completed, that may start only 25% of the flow into the Aqueonics system. All of the construction employees are still onsite for the next year. Trayham describes situations in which manhole covers were left off when a plumber hooked up a line from a new house to the collection system coming to the plant. “In those cases you have potential for torrential rains washing large volumes of silt and mud and everything else into the collection system,” says Trayham. “That’s a real concern for us; we don’t want all that mud going through our system and clogging everything. If you see that—it’s called an uncontrolled volume—you must isolate the plant at the flow equalization, call a pumper truck and then pump the flow EQ out.”
This problem is compounded by the fact that neighborhoods in the process of being built are also not landscaped yet. Any excess water will naturally flow to the lowest point. Any uncovered manholes, if they are in the lowest spot, can easily flood. “That material can be processed in our systems; but still you also run the risk of long-term exposure to sediment which tends to settle to the bottom of the tanks. We had to be onsite when this problem occurred: about an hour of torrential rains and pumping trucks to clear out our system to save the integrity of the process. The truck then took the material to an activated sludge plant which can handle those things.”
Measurement equipment in some sites allows remote monitoring with programmable logic controllers, PLCs. “I can monitor any one of our plants in New Jersey remotely any time I want to, even on the road with my laptop and my mobile phone, which I can connect to the Internet,” says Trayham. “In fact, during a recent trip to Australia, we spoke with a water corporation and they’re in the process of establishing a system at their central office in order to monitor 100 different plants that they own. Of course we are providing proposals for two replacement plants in which our PLC will be controlling and monitoring all of our process controls. That data will be sent both to their system and ours, plus we can also tap into the data anywhere in the US if we’d like.”
Most of the components that Aqueonics has now are discrete signals, which means it’s an on-off dry contact; the company also has analog signals—the flow control or flow monitoring for showing variations in milliamps from four to 20 of an electrical signal.
Aqueonics has also recently proposed a small system for a composting area for the County of Los Angeles for the treatment of the workers’ waste as well as the food preparation waste for the cafeteria operations on the site. They will also be taking a very small stream of the compost, treating by processing it to a guaranteed continuous drinking water standard so that it can be both either used at any time or discharged at will.
That site is therefore meeting California’s Title 22, the EPA’s most stringent standard for the reuse of water. “We already have some plants up and running in California which already meet Title 22,” says Trayham. “One of these is the Pullis Pines Plant in the Sierra Nevada Mountains of northern California.”
In the L.A. County proposal, to kill the bacteria to meet the Title 22 and the guaranteed drinking water standards, an upflow sand filter is used with the discharge, continuing on through a micro-filtration system. From there it goes through a long-path chlorination/dechlorination system. “That process will guarantee the destruction of any bacteria present in that wastestream,” says Trayham. “We just proposed systems in Western Australian that will do the same thing.”
For a 30,000-gallon facility, the footprint will be roughly that of a starter home.
A Perfect Fit
Osprey Point in Seaville, NJ, is strictly a residential development consisting of 149 age-restricted homes, up and running for the past two years. Aqueonics provided the onsite treatment, an alternating aerobic-anaerobic trickling filter system that handles a wastewater volume of 38,000 gpd.
As with another similar project to the north, in Hampton Township, NJ, the Osprey Point site discharges the treated wastewater back into the area aquifer; unlike the Hampton Township site, however, there were no problems with finding the best location for the most efficient percolation into the water table.
“From our point of view, the treatment system is quite unobtrusive,” says Bob Henzy, Sales Manager with Osprey Point Homes. “We’ve had zero complaints on the system, and it is onsite; yet, half the people here don’t even know it’s here. It’s quiet and odorless.
“We tell them when they purchase a home that we do our wastewater treatment onsite and that the system sits in the back. There’s no problem with it whatsoever. Though a small company maintains it, it is like a city here, so people don’t even think about it. As far as I understand it, the system can handle even more homes, too.”
Henzy can actually use the system as a selling point for those interested in environmental technologies. “We have a lot of people who come in, pick up our brochures and enjoy reading about how the system works.”
Every month a truck comes in and removes the solids. “The MUA takes the solids from us and other communities, they heat that, sterilize it and we buy the product back from them for use as fertilizer. Everything from the plant comes back here. When that product’s placed on the grass, it turns the grass emerald green. It costs $3 per cubic yard in addition to delivering it and letting us use their spreader for a dollar a day; it’s quite a savings.”
Osprey Point will also be using it on the community’s common garden. “It’s environmentally the safest thing you can put on the ground,” says Henzy. “Because it’s boiled there are no weed seeds in it. When grass seed is placed down, 27 days later there is a golf-course quality lawn in place. We are saving thousands of dollars.”
Peter Hildebrandt is a writer specializing in science and engineering topics.