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Water To Waste Section Twelve:Understanding northwest Michigan geography and geology and how this relates to wastewater.
1. Act of Redemption
An elderly widow in Acworth, Ga., thought her 40-year-old septic tank was leaking. The state-required soil test reported that the back and front yards of the three-bedroom home were unsuitable for a conventional replacement system.
Only a small area behind the garage had acceptable soil.
A solution eluded the homeowner for more than a month.
Cherokee County Environmental Health Department and contractors were unfamiliar with available advanced treatment technologies. If they couldn’t find an answer, the agency would condemn her house.
Designers John and Judy Fortune, of Aerobic Systems LLC in Buchanan, contacted underground plumbing division manager Scott Law of Superior Plumbing in Kennesaw. Within a week, they had an approved plan to install an extended aeration activated sludge treatment unit and low-pressure bed, the first in the county, on the woman’s half-acre lot.
The system, installed in October 2006, is functioning perfectly, and the home is no longer threatened with condemnation.
Soils are Type F, except for 1,500 square feet of shallow sandy clay loam with a load rating of 90 minutes per inch. Water table is 24 inches below grade.
The Fortunes sized the system to handle 500 gpd. Its major components are:
* Existing 1,000-gallon, single-compartment concrete septic tank.
* Aqua Safe AS500 package treatment plant from Ecological Tanks Inc., Downsville, La.
* 1,000-gallon polymer holding tank from NORWESCO’s Rochester product line, St. Bonifacius, Minn.
* Blaster 1/2-hp filtered effluent pump from Goulds.
System Operation: Wastewater gravity feeds into the septic tank, then flows into the round fiberglass pretreatment tank, which houses an aeration mixing compartment and center, cone-shaped, clarifier.
This tank sits inside the holding tank.
Air introduced at 2.5 psi mixes with the influent. Bacteria attach them selves to the bubbles, their oxygen source, and digest 97 percent of the pathogens as they swirl through the wastewater. A pressure switch on the control panel monitors the air pressure and sounds an alarm if it drops below 0.9 psi.
Mixed liquid enters the fiberglass clarifier from the bottom. Solids fall to the bottom in this quiet zone and re-enter the mixing compartment. Clear, odorless effluent continues to flow up to the 4-inch discharge pipe and into the holding tank.
“Georgia code requires holding tanks in the event of a power failure,” says Law. The low-pressure bed is demand dosed. Effluent averages 2.37 mg/l CBOD and 2.11 mg/l TSS.
When Law first evaluated the site, he determined that the drainfield was at fault. The shallow suitable soil behind the garage was barely acceptable and confined to a long, narrow space.
“John and I went over the regulations for a low-pressure bed and found that we had just enough room for the pit and clearance between the soil and water table,” says Law.
Low-pressure beds are hard to install on slopes greater than 8 to 10 degrees, so they are rare in hilly Georgia. Curtis Barnhardt, chief environmental health inspector in Cherokee County, had never seen one in 30 years of service.
While both tanks were being set, the excavator operator dug the 20- by 75-foot drainfield pit 18 inches deep, excavating from one end to avoid compacting the soils. “That afternoon, Barnhardt inspected the tanks and pit, which had to be level,” says Law. and he completely tested and inspected the system before trenching of the lines began.
After Barnhardt inspected the disposal bed, contractor’s paper was laid over the gravel to keep dust and dirt from contaminating it.
That night brought a downpour. Law knew the site would be a mudslide and dreaded going back.
“By luck, the gravel bed was as clean as when we installed it,” he says. The excavated soil covered the contractor’s paper. The remainder was incorporated into the back yard.
“It was such a mess with a lot of low spots,” says Law. “So we graded it, and seeded and strawed it for free.”
The State of Georgia will not grant an onsite permit unless a service contract accompanies it. Twice a year, a technician from Superior Plumbing which holds the 3-year service agreement, checks that the aerobic tank is functioning properly, cleans the air filter, checks the solids level, and checks household usage.
A Perfect Fit
Vermont’s revised waste-water regulations went into effect on July 1, 2007. Several North Ferrisburg residents decided to upgrade the systems on their lakefront homes. Richard Hurd, Chairman of the Long Point Homeowners Assoc., led by example.
His 100’ x 100‘ lot had a sequencing batch reactor installed in the early 1970's as part of a dry well system discharging to Lake Champlain.
When Brad Fischer of Bundy’s Sewer and Drain Inc. in Jericho inspected the unit, he found insufficient oxidization and broken baffles that allowed the system to pump itself dry. The unit was unsalvageable. “This site was very tough - the only room for a replacement pretreatment unit was on a deck overlooking the lake,” says Fischer. “That really limited our options.”
an important feature, since the site was inaccessible to large equipment and all work was done by hand.
The clay/ledge soil has a percolation rate of 120 minutes per inch or more. The water table is four inches below grade. A slope with a 3:1 grade rises at the side of the house, ending in a 6-foot-high stone retaining wall abutting Shore Road. An L-shaped concrete sidewalk comes down the hill and around the side to the back of the house,
System Components: Erwin sized the system to handle 360 gpd.
The standard is 375 gpd for a three-bedroom home, but pretreatment allows a 50 percent reduction in size.
The system’s major components are:
* 500-gallon Model CA-5 sequencing batch reactor from Cromaglass Corp., Williams-port, Pa.
System Operation: Wastewater gravity flows thorough a 4-inch, cast-iron lateral that surfaces after passing beneath the sidewalk, slopes gently for three feet, and enters the 6-inch inlet at the top of the three-chamber reactor. (The steel beam reinforced deck on which the reactor rests is six feet lower than the sidewalk.)
Flow enters the solids retention section, where a non-corrosive screen separates and retains inorganic solids. One submerged 1/3-hp aeration pump in the aeration section forces mixed liquor through the screen. The resulting turbulence, more vigorous than the action of a washing machine, breaks up organic solids.
Liquid and small solids pass through the screen into the aeration section The liquor is mixed continuously with air for aerobic treatment.
After the settling period, a 1/2-hp turbine pump with Sim/Tech filter discharges effluent through 1-inch PVC Schedule 40 pipe 35 feet to the 20’ x15’ drainfield. A submersible pump returns the sludge at the bottom of the clarifier to the aeration section. It takes less than four hours for an 80-gallon batch to reach the drainfield. Fischer programmed the system to cycle four times a day.
Erwin’s plans specified a mound sand absorption barrier beneath the driplines. Because the property sloped toward the lake and to meet regulations, the men first built three 2-foot-high retaining walls from pressure-treated 6-by-6 timbers to prevent the prewashed sand from eroding and to enhance the bed’s appearance. The fourth side was the stone retaining wall. 18” of sand were hand leveled leveled it with shovels and rakes for the drainfield.
On top of the sand went fourteen 18-foot-long laterals covered with 12 inches of bark mulch. “The Geoflow package contains valves, head works, and control panel,” says Fischer. “When the pumps shut off, the valves drain back, so no liquid is left in the driplines. That’s important because Vermont can have frosts and freezing weather through May.”
Maintenance: The state requires an annual inspection. Bundy’s Sewer and Drain Inc. does this on a service contract.
Because the home is seasonal, a technician pulls the pumps every fall and replaces them in spring. Any liquid in the reactor is pumped out in autumn to prevent it from freezing. Should a problem arise during summer, audio and visual alarms in the house alert the owners, and they call Bundy’s. The system is dormant in winter.
Water To Waste Section Two: Water / Energy Efficiency information and EPA WaterSense Program
Water To Waste Section Three: The inter-relationship between water use, wastewater, the water cycle and wastewater systems.
Water To Waste Section Four: Common sense information about how your wastewater system works
Water To Waste Section Five: Installation, siting, operation and maintenance.
Water To Waste Section Six And Seven: The many amazing things that end up in the waste stream and why we should be careful and concerned.
Water To Waste Section Eight and Nine: The state of our region - an attempt to survey wastewater systems.
Water To Waste Section Ten: The Case For Community Management
Water To Waste Section Eleven: Small community options, choices and solutions
Water To Waste Section Twelve: Understanding northwest Michigan geography and geology and how this relates to wastewater.
Water To Waste Section Fourteen: A terrible waste to waste - when there's money to be made and saved by innovation.
Water To Waste Section Fifteen: A word about who we are and our goals for the future - how you can help.
Water To Waste Section Sixteen: Gratitude to our sponsors and links to more information.
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