A Valuable Tool For The Future
Of Decentralized Wastewater Treatment
By Larry D. Stephens, P.E.
Stephens Consulting Services, P.C., Haslett, MI 48840
INTRODUCTION
Many have correctly stated that the key to the success of small-scale onsite wastewater treatment is proper management --- management that is as invisible to the homeowner as is that of a municipal treatment facility. I believe that most in our industry have accepted two basic premises:
• That all onsite treatment systems need maintenance
• That homeowners are not inclined to provide the needed maintenance
Some suggest that we need to do a better job of communicating with homeowners; admittedly, this is an area where we could improve. But, if we honestly consider the alternative of homeowner education to get the job done, we have an impossible task on our hands. First, we must convince homeowners that onsite system maintenance is necessary. Second, we must convince or require them to do it. Third, we must train them on how it is to be done.
In Michigan alone, there are over 1,000,000 households equipped with their own wastewater treatment systems. Recent figures indicate that somewhere between 22,000 and 28,000 additional new systems are permitted each year by 53 local health departments. If you combine these numbers with the fact that homes change hands every 5 years (by some reports) we have a formidable task. These local health jurisdictions would have to effectively train from 400 to 530 homeowners each, on the average, every year just to keep up with new systems. Consider the fact that this is only about 2.5% of the total number of systems existing in the state.
The alternative to homeowner management is some type of management authority, either public or private sector. Authorities in many areas are beginning the discussion of onsite system management programs, primarily because of the introduction of new technology. Taking the responsibility of operation and maintenance of onsite systems out of the hands of the homeowner and putting it into the hands of a motivated and trained specialist appears to be the answer.
One of the tools that today's industry is providing is the ability to manage small-scale systems using telemetry. This equipment provides us with the ability to monitor system performance, anticipate and troubleshoot problems, and provide continuous logs of flows and system performance for future decision-making.
Systems serving residential homes are not the only types of systems that benefit from remote management. Onsite wastewater systems are being installed every day at commercial, industrial and institutional facilities all over the United States, which would benefit from remote management. Although the circumstances and personnel vary with each facility, most of these facilities do not have maintenance people on staff that are both trained and motivated to properly care for their wastewater treatment facilities. Personnel do change from time to time, making it necessary to provide continuous training.
In the last two years our engineering firm has been responsible for the design of three projects that have incorporated remote management capabilities. I believe that these three projects do provide somewhat of a cross-section of the opportunities and benefits of where remote management can be an indispensable.
RIVER ROCK LANDING
River Rock Landing is a 29 home residential site condominium project located near Dimondale, Michigan, which is a small residential town along the Grand River just southwest of Lansing. This development is new, with just 5 homes now occupied. The property is located just far enough from the existing municipal sewer system to make the connection impractical.
Early site investigations revealed that the native soils on much of the site were clay and clay loam texture. It may have been possible to develop some of the lots using sand filters for pretreatment or pressure-dosed sand mounds, but the lot sizes would have to be larger, reducing the number of lots in the project. After further investigation, the answer that seemed most appropriate was the installation of a community "cluster" treatment system. An area was found where the permeability of the soil allowed the installation of an unlined pond that could be used to return the highly treated wastewater effluent to the groundwater. An N.P.D.E.S. permit was obtained to manually discharge the excess water from the pond to the Grand River, should it ever be necessary.
The treatment process that was chosen was side-by-side duplex recirculating sand filters, followed by side-by-side duplex intermittent sand filters. Facilities have been constructed to add alum to the recirculation tanks to precipitate phosphorus, but it has not yet been necessary. Collection of the wastewater is by means of a S.T.E.P. system with small diameter pressure sewers. The wastewater flow to be treated is estimated to be up to 10,000 gallons per day.
As long as the discharge to the groundwater through the bottom of the unlined pond exceeds plant inflow, the discharge to the river will not be necessary. If and when it becomes necessary to discharge the treated effluent to the Grand River under provisions of the N.P.D.E.S. permit, effluent quality will be monitored on a daily basis, and monthly discharge reports must be filed with the Michigan Department of Environmental Quality. The facilities are required to be operated under the supervision of a qualified and certified operator. A local public wastewater treatment plant operator has agreed to serve in this capacity.
As part of the management program for this facility, the developer agreed to have installed a telemetry panel at the treatment site. A dedicated telephone line is connected to this control panel, enabling a desktop (or laptop) computer with a modem to access it directly from any location. Water level sensors were installed in the tanks at the site, and in a stilling well hydraulically connected to the pond. The panel at this site is programmed to log and report on demand the following information:
• Current high and low water alarm conditions, and a log of past alarm events.
• Pump run events and run times.
• Water level readings in the tanks and pond.
• Amperage being drawn by pumps.
• Low liquid level in alum supply tank.
In addition to these monitoring functions, the program allows the remote operator to make system adjustments as follows:
• Adjust programmed pump run cycles (Time-off and time-on settings).
• Adjust alarm characteristics such as audible delays.
• Set and adjust high-level pump override cycles.
• Turn pumps on and off as necessary to correct a high water condition.
These capabilities do not eliminate the need for personal visits to the site from time to time to evaluate the performance of components of the system that are not visible over the phone wire. But we have found that the ability to monitor and manage this system on a daily basis, if desired, provides the remote operator with confidence in knowing that many of the common system management problems will not go unnoticed for very long. And, the numerous logs of system information provide a record of performance that can help the operator recognize trends, and troubleshoot problems.
An additional use of remote monitoring is being used on the latest S.T.E.P. system that was installed at River Rock Landing. The latest home and all new homes will have the pump control panel connected to a shared telephone wire by which all pump run times and events, and any alarm events are being monitored.
POHL OIL TRUCK STOP / McDONALDS EXPRESS
Much like many truck service facilities, this site is located at an interchange along an interstate highway over two miles beyond the service area of public sewers. Located just north of Grand Ledge, Michigan, the site was chosen for this facility based upon its location and accessibility, not because it had soil conditions acceptable for an onsite wastewater system. Due to the size of the site and the nature of the soil conditions, it became necessary to pre-treat the wastewater before discharge to a soil absorption system. Design flows for this facility were estimated to be between 2,500 and 3,500 gallons per day.
The treatment process chosen for this facility begins with the McDonalds Express kitchen portion of the facility being served with a large dedicated septic tank. This consisted of a 1,000 gallon grease trap followed by a two-compartment, 2,000 gallon septic tank, fitted with an effluent filter at the outlet. From there, the effluent from the kitchen tanks is co-mingled with the raw wastes coming from the public bathrooms and showers (provided for truckers). The combined wastewater is directed through two 2500- gallon septic tanks in series, which are again equipped with an effluent filter at the outlet.
The septic tank effluent flows from the septic tanks to the treatment site where it enters the first of two 2,500 gallon precast concrete tanks that are connected near mid-depth. These tanks serve as recirculation tanks for a pair of recirculating sand filters. As the septic tank effluent enter the recirculation tanks, it is mingled and diluted with return flow from the sand filters in a ratio of about three parts return flow to one part incoming effluent. Pumps located in this tank dose the sand filters in programmed fashion. Final treated effluent from the sand filters flows to another dosing tank where another pump doses a soil absorption bed on a programmed basis.
The pump controls at the treatment site are all combined in one panel that is equipped with telemetry accessible over a dedicated telephone line. Water level sensors have been mounted in the tanks at the treatment site, and water meters have been installed on the raw water supply coming into the building and on the final effluent line going to the soil absorption bed. The various parameters listed for River Rock Landing are also being logged and reported here, along with the additional flow information being measured by the water meters.
Design flow estimates for facilities such as this boil down to an educated guess using limited water use information from other facilities. We have found this kind of information to be hard to come by, and highly variable. It is almost always based upon water use, and not actual wastewater flow information. My experience has been that both the review agencies and the engineering profession are not vary comfortable with the information that is available to provide a basis of design for such establishments. With the use of telemetry panels such as this one at Pohl Oil, we can begin to accumulate a large amount of good solid flow information for such facilities. If this information is archived, we will eventually create a large database of reliable available design information.
ISLAND CITY ACADEMY
The site for this new charter school just outside of Eaton Rapids, Michigan, was also one that required pre-treating of septic tank effluent before application to the soils on the site. The native soil conditions were marginally permeable when considering estimated peak flows from this school to be around 5,000 gallons per day. The pretreatment process chosen to follow the septic tanks were again a pair of side-by-side recirculating sand filters. Final discharge of the treated effluent was to a series of pressure-dosed soil absorption trenches.
Island City Academy is school facility that is part of a recent explosion of charter schools in Michigan. This movement to schools of choice does mean that the student body size is not as predictable as it once was. Growth of a public school district at one time paralleled the residential growth of the community. With schools of choice, institutions are now competing for students, with their degree of success dictated by their program and marketing efforts. This school does have some room for expansion, so it will be very important to monitor and document flows being processed at their wastewater treatment facility for future decision-making.
The wastewater treatment facility at this school was provided with a telemetry panel that has the ability to monitor and report pump run times and events, as well as alarm conditions and logging as previously listed. Programmable timing features can be adjusted and pumps actually controlled remotely as previously described. Daily flow information is being logged for future reference as needed.
A recent event illustrates how helpful this remote monitoring capability can be. In July this author received a telephone call from a secretary at the school. She said that several of the toilets in the building would not flush properly. This was strange to her, because there had been no one in the building for some time. School was not in session for the summer, and she was rarely there. She wondered if I could check the treatment system to see if everything was working properly. Agreeing to do so, I said I would call her back in a few minutes.
This school is about a 45-minute drive from our office. Had we not had the telemetry panel installed, this investigation would have required a drive to the site --- at least a two-hour commitment. But instead, I walked over to my desktop, dialed up the treatment panel at Island City Academy, found everything normal, and called her back within 10 minutes. She thanked me and told me that she had already arranged for the drain cleaning firm to come out the next day to check the building plumbing that was apparently plugged.
I was also able to go over with her on the phone when I noted that there had been flow in the system on two or three occasions during the previous month. She said that those all made sense because they had hosted some meetings at the school on those days.
SUMMARY
These remote management capabilities are the future of our wastewater industry. Through the use of telemetry on the systems described above, during the past year alone our firm has been able to:
• Document flows from several facilities.
• Adjust timer settings during start-up of treatment facilities.
• Find a leaking septic tank.
• Verify the treatment system was not the cause of toilet malfunction on two occasions.
• Monitor pond water levels and water levels in tanks.
• Find and correct a siphoning condition in a S.T.E.P. tank.
Wastewater treatment facilities at both commercial and residential facilities can be remotely managed economically with today's technology. Home and business owners, in general, are neither motivated nor trained to properly maintain their own wastewater treatment facilities. This "management from afar" by qualified service providers can be a major tool toward making the operation and maintenance of small-scale wastewater treatment facilities "invisible" to the owner.