And...another update from Dr. Agar, who has now done some homework and ended up in a direction we never would have thought of. Here's what he found:
"First, I can find NO INFORMATION in the PD or dialysis literature to answer this lady’s question … Zip!
We have known here in Geelong for a long time that the post dialyser saline effluent from HD should NOT be directed to a septic system as the saline damages the bacterial and fungal ecosystems that at vital to septic tank function. Indeed, I have included this information in my papers and editorials in HDI on the topic of Green Dialysis and it is included as an instruction for home HD patients in the waste-water management section of our eco-dialysis website of ‘how to make dialysis green’ … http://www.greendialysis.org.
So … in HD, it is clear … don’t discharge to the septic!
As no such relationship has – to my searching – been reported in the literature, I went searching.
Ha! While the dialysis literature is void, the wine-making literature is not! There is a wealth of information for small wineries warning not to discharge the sugar-rich effluent from the crushing process into anaerobic septic systems. While this this effluent may vary in its sugar content over the wine-making cycle from 1000 to 5000 mg/L, over this limit will clog and damage the septic system as a gelatinous co-polymer forms over the surface of the septic bed and in the feed and outflow pipes. There is a recommended maximum sugar concentration for winery effluent into septics of 5000 mg/L
PD solutions are 1.5 – 4.25% (note that this % = grams (not mg) per 100ml).
This is equivalent to 15 grams per litre (or 15,000 mg/L) up to 42.5 grams per litre (or 42,6500 mg/L) = an order of magnitude 10 x that of the recommended upper limit for sugar concentrations into an anaerobic system. Combine that with a small surface area system and a low total daily water flow and it is a recipe for system failure.
Apparently, some form of ‘clear gelatinous co-polymer forms’. I have emailed the Curtin University Department of Environment and Agriculture in Perth for some explanation of the underlying chemistry of this but have only just done so and have not yet heard back. Curtin have conducted research for the Margaret River wine region of Western Australia on this issue, and this has led to their publication of a series of fact sheets for the Wine Industry, and a series of effluent regulations around size of septic system relative to water flows and the ‘substance content’ of the effluent … with one of those substances being sugar!
So, Dori … the short answer to this lady and others is: don’t discharge PD effluent into a small anaerobic septic. It will rapidly generate a clogging co-polymer that blocks up the septic.
We will research this further, with a likely warning to this effect added to our green website information base.
As 252,000 PD patients exist world-wide, it may be a topic of relevance to others – and one that your readership becomes aware of.
If further information comes to light, I will let you know. If others are interested in the chemistry behind this, let me know and I will come back to you with the answer – if or when I get them.
So, now the obvious question is, what CAN you do with the PD drainage if it can't go down the toilet into a septic system? Good question. For now, Dr. Agar's answer was, "dig a pit in the garden." But, he is still looking into it, and there may be other ideas.