The phrase reduce, reuse, recycle is purposely listed in order of sustainability. It is always better to reduce our consumption, then reuse products, and only then to recycle as much as we can.
Living with the earth instead of just on it has some unexpected benefits – such as the delight we felt when we sold our lawn mower. Before we built here, the land was maintenance-free woodland. After we built, it was still maintenance-free woodland because of our green roof.
Last time I covered waste management, which, I’m convinced, is better than waste covering me. We looked at privies, composting toilets and the environmental problems of septic tanks. This time, as promised, we will investigate the two most responsible ways to handle your waste: peat moss systems and biofilters.
In a peat moss system, water from the dwelling first collects in a conventional septic tank where the solids settle. The clarified effluent then drains, or is pumped, to the peat filter. The peat acts like a sponge, absorbing and wicking the effluent and providing treatment as the wastewater slowly filters through. Eventually the effluent filters to the bottom of the peat where it percolates into the soil for final disposal.
We might not think that filtering through peat would have any treatment effect, but according to the Barnstable County Department of Health in Massachusetts, experimental results show that peat filters are capable of very efficient removal of fecal coliform bacteria, biochemical oxygen demand (BOD) and total suspended solids (TSS). They also appear to be capable of producing a significant reduction of total nitrogen in the finished effluent. This is important because it can avoid unwanted plant growth in the dispersal area.
The great advantage of a peat system is that most of the treatment can be contained in a large, above-ground box with a minimal drainfield. This makes the system ideal for rocky areas where installing a below-ground system with a conventional drainfield is difficult and expensive.
But, you can’t just buy garden peat moss and build a system yourself. The peat must be air-dried, have a very specific moisture content and a precise degree of decomposition. Peat meeting these specifications is mined from peat bogs specifically for use in peat filter systems.
This peat has unique chemical, physical and biological properties that contribute to sewage treatment. The peat bed holds up to 20 times its weight of water, and this stabilizes the internal temperature, nurtures the natural microbial population in the peat when the system is not being actively used, and maintains performance even in very cold conditions.
The moist, spongy environment gives the effluent a long residence time in the peat. As the wastewater is wicked through the peat, it flows in a thin film over the surfaces of the peat fibres. This allows the effluent to become aerated, exposed to the acidic chemical environment of the peat and come in close contact with the microbiological community inhabiting the peat. Solids that are larger than the channels in the peat are trapped on the peat fibres as the effluent trickles through.
Within several weeks of use, the peat filter is colonized by a range of micro-organisms and invertebrates from the septic tank effluent and the surrounding soil. These include bacteria, fungi, protozoa, nematodes, earthworms, rotifers and others. Treatment of the septic tank effluent is performed mainly by acid-tolerant bacteria and fungi living in the peat media.
Because of the high organic content, the peat must be periodically replaced. This means physically removing the peat when it has begun to decompose. Life expectancy depends on usage, but 10 to 15 years is average. Make sure your system is designed to make it easy to remove and replace the peat, and have your installer give you a firm quote for maintenance and peat replacement.
A peat system is usually more expensive than a conventional system, but much cheaper than trying to put a conventional system in difficult circumstances. This makes it ideal for small lots and cottages. Plus, a peat system typically provides better treatment and a cleaner discharge than a conventional septic system.
Biofilters act much like peat systems; they rely on the biological treatment of wastewater. Household sewage goes into a septic tank where the solids settle, then through a filter. The clarified effluent is sprayed over non-biodegradable foam cubes that provide a foothold for the bacteria that treat the waste.
The final water that is released is exceedingly clean, which was our reason for going with this system since we are next to the Salmon River. Our manufacturer claims we could drink it, but our confidence level is not quite that high. Nevertheless, we believe that this is the cleanest sewage-treatment method available.
Our biofilter system is housed in a small, above-ground shed 2 metres high, 1 metre wide, and 2 metres long, above a 3-metre diameter drainfield. Most biofilters can be installed above or below ground.
Biofilters reportedly have several benefits. We have only had ours for six months and can’t attest to them all, but it has worked well for us so far:
- Low maintenance: The non-biodegradable filter medium normally does not require cleaning or changing for 20 to 30 years.
- Low energy: A small intermittent pump is the only energy requirement.
- Recoverable: Easy to recover if the septic tank fails, unlike sand filters or conventional tile beds.
- Flexible configuration minimizes tree cutting and excavation.
- Small footprint: Effective treatment in an area five to 10 times smaller than that of sand, soil or peat beds; and 10 to 50 times smaller with recirculation or deeper beds, especially useful for larger systems.
- Applicable in many locations: bedrock, clay, swamp or small lot.
The cost of a biofilter is comparable to a high-end, conventional septic system, but because the results are so much better, that cost is justified no matter where you live.
So, we’ve come a long way from using bushes or throwing our night soil out the window in the morning. Both peat and biofilter systems co-operate with nature to process our waste, and that co-operation is always the best way.
Let’s treat the earth as if our lives depended on it.