The 1998 Master Composter Excursion:
"How the Bugs Do It on Vancouver Island"
"Low-Tech Wastewater Treatment"
By Wendy Steffensen
FIELD TRIP BACKGROUND:
What to do- what to do- Labor Day Weekend, 1998.
Of all things planned and possible, our group of the intrepid six (master composters, friends, and relatives) decided to forgo the amazing music festivals of Puget Sound and head across the border to Canada’s Vancouver Island to see, yes, you heard right- a wastewater plant. Here we forged lasting interpersonal bonds- the kind made possible only by waiting in holiday-weekend lines at border crossings and ferry terminals and by peering over tubs of poop (er- wastewater).
We did have a fun and interesting time during our educational outing. Read on to see what you could have learned first hand, had you not gone to BUMBERSHOOT.
We learned that A SOLAR AQUATICS WASTE DISPOSAL SYSTEM:
SEPTIC TANK SYSTEMS:
In these systems, household waste is funneled to a septic tank in which solids settle out and form a sludge layer. The liquid flows into a drainfield by means of a network of perforated plastic pipes surrounded by crushed stone. The sludge is typically pumped out of the tank every 3-5 years and hauled to a conventional wastewater plant. The liquids contain high levels of bacteria, nutrients, and organic compounds. As the water filters through soil, the bacteria die off or cling to soil particles, and the nutrients and organics are taken up by the soil biota. In a properly functioning drainfield, contamination of the groundwater is negligible.
CONVENTIONAL WASTEWATER TREATMENT:
Here, waste is collected from homes, businesses, and institutions via underground pipes and it is routed to a central location. The waste is treated physically by screening and settling the wastewater (primary treatment). Next, it might be treated biologically using bacteria that break down organic waste (secondary treatment). Chemical treatment is applied to further reduce organics, nutrients, or toxics if necessary (tertiary treatment).
Typically, after the solid waste is separated by settling, it is incinerated or, after further treatment, land-applied. Water is discharged or further treated for drinking water.
Regulations on discharged wastewater usually include limits on the number of fecal coliforms (bacteria used as indicators for fecal contamination), the amount of suspended solids, and the amounts of degradable matter (termed biological oxygen demand). Diminishment of fecal coliforms, suspended solids, and biological oxygen demand is aided by chlorination, primary treatment, and secondary treatment, respectively.
SOLAR- AQUATICS SYSTEM at Englishman River TRAILER Park:
Historically, waste at the Englishman River Trailer Park (ERTP) on Vancouver Island was treated with septic tanks and a common drain field. In recent years, the septic tanks and drain field at ERTP was failing; sewage was leaking from broken pipes before adequate treatment and passage to the drainfield. Instead of making the necessary repairs to the existing system, the more cost-effective solar-aquatics waste treatment system was built.
In the Solar Aquatics System, waste is collected, blended, aerated, and gravity-fed through a system of solar tanks. As with the secondary treatment process of a conventional plant, the bacteria within the waste degrade the complex organics into simpler organic compounds. The last tank in the series is called a clarifier, and it is where the sludge, or settled solids, is collected. Unlike a conventional plant, the sludge is taken from the clarifier and retreated many times until just a small amount of it remains. This small amount is considered non-degradable; it is collected and hauled away.
The solar aquatics system, different from conventional processes, contains plants, snails, frogs and fish, as well. The plants take up nitrogen, phosphorus, and metals from the waste and provide aeration and root surfaces on which biofilms of bacteria can grow. The snails, frogs, and fish pass freely between the tanks, finding suitable habitat, eating sludge and each other. Excess plants are routinely composted to keep the percent tank coverage by plants at optimum levels.
For more information on phytoremediation, the use of plants and trees to clean up contaminated soil and water,check out the EPA site on the supject: http://clu-in.com/citguide/phyto2.htm
Another great site that explains water recycling systems and shows pictures and architectural drawings of waste water systems as well as many references is: http://www.waterrecycling.com/index.htm
Passing it through a sand filter and a marsh system further treats water that is recovered from the final clarifier. The numbers on fecal coliforms, suspended solids, and biological oxygen demand from this solar aquatics system are comparable to that from a well-run conventional plant. (I checked)
WE WERE IMPRESSED!
DATA (FOR THOSE OF YOU WHO LIKE THIS KIND OF THING):