The GOSEP back-story

Over the last 35 years Dean Cameron has observed the way ecosystems process organic matter and gradually came to understand that conventional engineering approaches to sanitation and waste treatment have been led down the wrong path because of two popular innovations that separated people from their natural aversion to the odour of their own bodily wastes. The earliest innovation was pipes and drainage systems designed to remove contaminated/used water, and the second was the flush toilet. These inventions transformed the lives of urban people. No longer did they feel the urge to throw the objectionable contents of their chamber pot into the street or take precarious trips to the out-house on dark rainy nights. Their unsanitary “wastes” could be flushed “away”. In the first instance “away” was the nearest gutter or waterway, but this only transferred the offensive materials and odours into a street or stream nearby. It was quickly realised that wastewater could easily overwhelm the ability of waterways to naturally treat the wastes and was upsetting the natural balance and killing fish and other aquatic life as well as people.

This is the origin of the fundamental mistake, the original sin of sanitation engineers, they saw wastewater as a contaminated aquatic system and based their treatment solutions on what they observed happening to the organic matter when it as left in the water rather than thinking about how best to get the waste out of the water as quickly as possible.

Sanitation engineers observed three basic processes.

1. Heavier particulate matter settled to the bottom of the wastewater column and did not decay much (in fact it is pickled and can remain clearly identifiable as corn, peas or carrots etc for many years until it is pumped out of septic tanks or settling ponds)

2. Lighter material floats to the top and forms a crust that is exposed to the air and breaks down slowly to humus and given time can even develop a soil like ecosystem containing earthworms and insects.

3. The water zone between these two layers depletes all of the oxygen originally contained in the water due to microbial fermentation and soon becomes anaerobic, odorous and typically black in colour (hence the term blackwater) for septic effluent.

These three processes lumped together are referred to as primary sewage treatment and form the basis for the design of the default minimum standard for wastewater treatment, the septic tank. The tank size has to be large (costly) enough to allow the peak hydraulic flow rate to be slow enough to allow the heavy and light solids to separate and not just be carried out of the tank and block the trenches. Even when sized correctly the primary septic process produces effluent that still contains about half of the wastewaters original organic matter food value (BOD₅) and many of its original microbial pathogens, so it still needs further treatment. The blackwater effluent also smells bad and so is typically “disposed of” in underground trenches where it will hopefully be further treated by subsoil microbes and eventually make its way into the groundwater, ideally without bypassing treatment through root channels and other soil macropores and so contaminate wells and bores. In addition to this obnoxious effluent output, primary treatment produces methane, CO₂ and unpleasant odours. These greenhouse gas emissions are vented to above the roof line through the building drain pipes and vents. Last but not least is the septic “sludge” output. After a few years so much settled sludge accumulates that it must be pumped out and carted to either secondary treatment systems, oxidation beds, composting operations or landfill. Sludge treatment can be a significant and ongoing cost of both primary and secondary treatment systems.

On the face of it primary sewage treatment only seems logical if you don't consider what alternatives could be used if we employed lateral thinking! Sedimentation, floatation and anaerobic digestion only remove about half of the contaminants that were originally in the sewage. Biogenic methane production is discharged to the atmosphere and not recovered. And most importantly a difficult to treat and obnoxious smelling pathogenic effluent that is prone to clog the subsoil has to be disposed of below ground. Lastly the septic sludge requires a dedicated pump out and treatment/disposal infrastructure that is costly.

The septic tank is the quintessential product of the aquatic mindset trap.

Furthermore secondary and advanced treatment are just a further and more expensive extension of this aquatic treatment mindset trap. As microbiology and biochemistry advanced it was realised that wastewater that was agitated, injected with fine bubbles or otherwise exposed to air would not go anaerobic and that the organic “food” within it could be decomposed much more rapidly and the pathogens within it could be consumed and neutralised by aquatic aerobic microbes. Instead of only removing 50% of the original food value in the wastewater as for primary treatment, 95% or more could be rapidly metabolised with secondary treatment. Some of this remaining 5% could then be physically removed as settled sludge by sedimentation prior to disposal or further treatment and even reuse. The biggest cost of secondary treatment is all linked to oxygenation. It is energetically costly to pump oxygen into water. even in ideal conditions water at 20°C can hold less than 10 parts per million of dissolved oxygen. By comparison air contains over 200,000 parts per million of oxygen, 20,000 times the saturation concentration in water. What this means is that what happens for free in a soil ecosystem treatment method where moist wastes are surrounded in air with thousands of times the oxygen available for rapid breakdown, can only be accomplished in an aquatic treatment system with lots of electrical input needed to pump or blow small amounts of oxygen against a concentration gradient into wastewater. Secondary treatment is still considered a big advance but this view can only be sustained when considered in relation to primary treatment of raw used water. In comparison to aerobic soil based treatment systems all aquatic based wastewater treatment systems are slow, energetically inefficient, have a high greenhouse gas footprint and produce lower quality effluent treatment and environmental outcomes.

The case for a new wastewater treatment paradigm is compelling. To graphically illustrate why this is the case consider the following experiment.

Aquatic vs Soil filtration comparison experiment;

• Take a large dog turd that you have picked up while walking your dog.

• Weigh the turd on several folds of toilet paper.

• Now place the turd and toilet paper gently in a bucket containing 4 litres of tap water (the flush volume in a water efficient toilet).

• Stir it gently with a stick to simulate the effect of it being flushed down the toilet and through the pipes to the treatment system.

• Weigh a wetted paper kitchen towel.

• Now filter the contents of the bucket through the wet paper kitchen towel folded into a funnel (it will only take a few minutes for the water portion to fully flow through the wet paper towel).

• Now weight the wet paper towel with the filtered out portion of dog turd in it.

• look at the Turbidity of the filtered water and smell it (it will look surprisingly clear and have surprisingly little odour (less than 10 Nephelometric Turbidity Units (NTU)).

• Now place the dog turd and filter paper on the surface of a worm farm and observe how long it takes to disappear. (typically in 3 - 4 days - or less for human faeces)

• Estimate what proportion of the wormfarm surface layer was taken up by the paper towel package. (if it takes up 1/20th of the surface then 20 such packages could be digested every 3 - 4 days)

Discussion:

If you conduct this experiment you will find that for each 100g of turd less than 0.1g will flow through the filter with the water. Now to fully comprehend what this experiment means let's compare that to typical results from aquatic based conventional primary and secondary treatment that would take a day or so to achieve.

In a septic system about 50 grams of the turds weight would pass through in the effluent. In a properly operating secondary treatment system producing the required effluent standard of a 20mg/l Biological Oxygen Demand (BOD₅)/30 mg/l Total Suspended Solids (TSS) effluent 0.120g of solids (microbial mostly) would still be in the effluent! The simple filtration method is much better than primary treatment and significantly better than secondary treatment. If the filtration medium is changed from paper to sandy loam soil then effluent treatment performance will be at least an order of magnitude better than for secondary activated sludge aquatic treatment.

As a general rule, the longer organic waste material stays submerged in water the harder it will be to treat because the soluble portion of the organic matter will dissolve and the microbes in the waste will rapidly deplete the free dissolved oxygen in the water and start creating odours. Also the more the organic matter is agitated and broken up the faster the soluble portion will dissolve.

It should be obvious that not only is the cost of making and installing a primary treatment tank unnecessary for good treatment, it is actually an impediment to the genuinely effective treatment stage for any septic system, which is the soil infiltration stage. Anaerobic effluent from a septic is toxic to worms and other soil fauna which benefit the soil greatly by incorporating organic matter thus improving the soil porosity and treatment capacity.

All of the tanks, pumps, blowers and electricity of secondary treatment systems are only necessary because they are rooted in the aquatic treatment mindset. It's time to “think outside of the tank” and re-imagine wastewater treatment by collaboratively observing and documenting the amazing power of moist soil ecosystems to break down wastes and cooperatively emulate them using the simplest possible infrastructure. Pipes and flush toilets are wonderful sanitation advances but have given us the problem of wastewater to deal with. Aquatic treatment of wastewater is a deadend we need to abandon.

Filtering out the organic matter from the water within the first few minutes after wastewater is generated and surrounding it with free air and a diverse yet stable community of soil organic layer organisms, both macroscopic and microscopic is not cheating, it is just a whole lot smarter than pushing an unstable and easily perturbed aquatic microbial ecosystem past its natural limits.

GOSEP is a creative collaborative development response to take the best of the known sanitation solutions and deliberately engineer and evolve them into a robust ultra-low cost yet super effective solution that can be implemented virtually anywhere in the world where temperatures can be maintained above 10-15 °C and below 32-35 °C. Significant progress and proof of concept has already been achieved towards this goal.