Great information - thank you.

Dear Ian,

Thanks for this info. I am glad to see that formaldehyde does break down over time.

From the Wikipedia Formaldehyde page, I navegated to
sitem.herts.ac.uk/aeru/ppdb/en/Reports/359.htm
which states that for soil degradation, it has a typical DT50 of 6 days, sometimes reaching to 20 days, and that it does not remain persistent in the soil.

Thanks for pointing out that it breaks down into CO2 and water. It also does not include toxic elements, like mercury.

It seems there should be no problem applying Deep Row Entrenchment directly, on open land, at a prudent distance from streams and rivers, plus the groundwater being deep. It does not seem feasible to put this sludge in ponds first, especially since we are in an earthquake emergency and such waste stabilization ponds do not likely exist in the area.

Best wishes,
Chris Canaday

Hi Chris,

Most people that provide chemical toilets use folmaldehyde or other aldehyde products as they are much cheaper than the alternatives which we tend to consider more environmentally friendly. However formaldehydes are not actually a problem in a diluted form. Most of the commonly used holding-tank chemicals contain formaldehyde and are toxic or inhibitory to wastewater at full strength, but completely biodegrades with dilution and time. It breaks down into simpler molecules (like carbon
dioxide and water) through the natural action of oxygen, sunlight, bacteria and heat. The
biodegradation is considered to be faster than most other deodorant products, and therefore
formaldehyde-based products are considered the most effective holding tank chemicals
available.

For shock loads of formaldehyde to aerobic systems, the half-kill dose (= 50 % reduction in biological activity) is as much as 200 mg/litre. For continuous loading, the minimum half-kill dose is reported as about 20 mg/litre, but bacteria will acclimate to eventually remove larger concentrations of formaldehyde. For anaerobic treatment, the critical formaldehyde concentration is slightly higher than for aerobic treatment. When formaldehyde is discharged to septic tanks, it could lead to bacterial die-off and clogging of the french drain. The critical concentration is
reported to be about 250 mg/litre, which is much higher than the estimated values of
formaldehyde in chemical toilets.

So you should not be concerned about adding the content of chemical toilets to an existing wastewater treatment works if you remain within these parameters - which will normally be the case. If you want to use deep row entrenchment, it may be an option to first use a lagoon to allow for partial degradation and partial dewatering, followed by entrenchment of the sludge. The main problem with stinking toilets would be that they are not replaced at the required frequency. The main concern on small wastewater treatment works may be the much higher organic loading from chemical toilets (about 20 x more than sewered waste) rather than the presence of formaldehyde.

This information comes from a study undertaken by the University of the Witwatersrand in South Africa where this concern had been raised.

Dear Marijn,

Thanks for your input.

I will investigate what they are using. I think it is mainly a matter of private Ecuadorian companies (which may or not be scrupulous).

What should be done with faecal sludge that contains formaldehyde?
Are there other ingredients that are also unacceptable?

So, if those chemicals are not present, we will promote Deep Row Entrenchment.

I will write to Doctors Without Borders, who is running one of the main camps.

Best wishes,
Chris Canaday

Dear Chris,

I hope things are improving post earthquake, and that you are not having too many aftershocks.

Regarding your question. Have you checked with the suppliers of the toilets, or on the packaging of the disinfectants, what is actually in them? It seems there are non-formaldihyde mixtures for these kinds of toilets these days. I would be surprised if aid organizations still use Formaldihyde based products, as it is commonly agreed to be very nasty stuff.

If you are sure that ground water is not an issues, deep trenches are probably a realistic solution to get rid of the sludge.

Regards

Marijn

Hi everyone,

I am helping to analyze and improve the sanitation in the emergency relief camps after the Ecuador Earthquake. Many of the camps have stinking chemical toilets ("portapotties") and I saw on the internet that these tend to include FORMALDEHYDE to control the bacteria that generate odors.

I highly doubt that this faecal sludge is being treated at all, but what would the proper treatment be?

Is there a more environmentally friendly recipe that we can promote? In that case, would you agree that Deep Row Entrenchment is a good option (given that this is a dry area with mostly deep water tables and it is the beginning of the dry season)?

Other suggestions?

Best wishes,
Chris Canaday