12 YEARS WITH A COMPOSTING WASTE WATER DISPOSAL SYSTEM

The system's main components

As mentioned in the last post we recently had trouble with the pump that moved water from our worm farm waste water disposal chamber to the underground distribution system. As many people who come on our permaculture tours are interested in the system, we thought we would elaborate on how it works and review its performance over the past 12 years.

The system is called the A&A Worm Farm Waste System (designed and built in Australia) and we are very happy with it. All waste (bathroom, toilet and kitchen) flows by gravity to a storage chamber (the worm farm). Solids form a compost heap in the tank and liquids gradually drain through into the sump. A submersible pump activated by floats takes a couple of minutes to pump the liquid to the disposal area where the waste is dispersed underground.

 

Our plan is to one day run this waste water through reed beds and then use it to water fruit trees. It is possible on some sites (in fact desirable) to have the whole system run by gravity. This would negate the need for a pump, and the only need for power would be to charge the battery on the alarm system which lets you know if the system is not working properly.

The rechargeable alarm

There is a compost bin on top of the chamber for adding other organic matter. We dispose of cardboard boxes and invasive weeds through this, to give the worms some variety in their diet. 

Over 12 years we have had some large parties and events and the system has coped well. The solids in the chamber have reached about the halfway mark and seem to have stabilized at this level. As the solids are broken down by microbes and worms, small particles get flushed out with the water.

We see the system’s main advantages as:-

·                 The waste water can be put to use in orchards or grassy areas

·                 Minimal power use (Almost nil if gravity is used instead of the pump)

·                 The cost of the system is reasonable with no ongoing maintenance contracts (like some other systems)

·                 There is virtually no odour – even when the access lid is lifted up

·                 A simple design that doesn’t require specific technical knowledge and problems are easy to diagnose and fix

·                 Most of the time there is no maintenance required at all

·                 The compost chamber allows easy disposal of persistent weeds and other organic matter

Looks like a compost heap inside!

 

How has it performed?

Even though we have had occasional issues that need attention, we think its performance over the 12 years has been excellent.  During this period it has largely operated day in and day out without us giving it a second thought.

The issues that have arisen with the system have mostly been of a minor nature and were easily fixed.

• Stuck floats. A couple of times the floats that turn the system off and on have become stuck. Usually the solution is to give the sump outflow pipe a shake and this frees them up.
• Build up of sediment. Every year or so we pull the pump out of the sump, wash it down, inspect it and empty any sediment that has built up in the bottom of the sump. The pump is not designed to cope with sediment so this is more of a precautionary measure.
• Pumps have a limited lifespan. Our issue with the pump was detailed in the last post
• Blocked Disposal trenches. This took a bit of effort to solve, but was very site specific. During the drought (years of very dry conditions) the ground surrounding our disposal trenches dried out to such an extent, it had set like concrete, and lost the capacity to absorb water. We would have had the same issue with any system of underground distribution of waste water.  In these conditions our soils were just not capable of absorbing the required amounts of waste water quickly enough. We replaced the first few metres of the installed underground distribution channels with Plastic Domed Drain Material which had a much bigger capacity and was capable of holding the waste water long enough for it to be absorbed over a longer period of time.

Domed drainage added to each absorption trench

 

Most of our issues were relatively easy to solve in retrospect. They were also part of the process of learning about how the system works, its limitations and maintenance needs. This last point is part of our basic philosophy – to take responsibility where possible for growing food, generating power, harvesting rain water and disposing of our own waste. Life has become one huge learning experience!