This is an archival version of the original KnowledgePoint website.

Interactive features have been disabled and some pages and links have been removed.

Visit the new KnowledgePoint website at


Decontamination of ground using lime


Areas set aside for cooking spaces, temporary learning spaces, etc have been used as defecation areas and are quite polluted, with (in some cases significant) human faecal matter as a result.

The pollution will have permeated below surface, what would be the best material or processes to decontaminate the ground in order that these areas can safely be redeveloped as cooking, child friendly, temporary learning spaces without health risk? It has been proposed lime be applied. Is this the most suitable option or are there preferred alternatives? If lime is to be applied what would be the appropriate application quantities?

We are based in Sri Lanka.

3 Answers


Personally, I wouldn’t even think about putting these spaces on former defecation fields.

Surely this should be the basis to advocate with Govt for more space elsewhere? Or push for full/partial camp population relocation, as required?

I would fence the areas off completely for human use as public health risks are too great. Cholera outbreak in a high density camp carries too high a mortality and morbidity risk, responsibility for which would presumably be carried by intl community if you sanction this move…

What about WHO? Are they involved to advise in-country? If nothing else to share burden of risk if you end up going ahead.

Pete Mansfield

Harriette Purchas

The problem

• a shitty field

• a shortage of space

• lots of people

Possible solutions

• Don’t use it – but the alternative may be worse so you will have to weigh up risks

• Best solution – scrape if off – may not be possible – we are talking about say 20cm and even then no guarantee that there is not some pollution left

• Next best – cover it – same problems as scraping it off – a lot of earth

In-situ treatment needs:

o High pH – lime would help but would not disinfect only reduce the time required by a modest percentage through raising the pH

o High temperature – but Feachem et al quote for composting figures of 62C for 1 hour, 50C for 1 day, 46C for 1 week, 43C for 1 month and 42C for 1 year for the inactivation of all excreted pathogens with the possible exception of Hepatitis A

o Low humidity – almost certainly a challenge in Sri Lanka and little that can be done?

o Time – measured in months, see above – we assume that you don't have this luxury

o So on balance any on site treatment may be tokenism with the exception of scraping or covering

I'm well aware that we have not come up with a magical solution, but unless someone else does, perhaps the best we can offer is confirmation that one does not exist - apart from scraping or covering.

Tim Foster


I won't claim to be an expert, so I might be out of line here and should let others handle this. Could the decay process be accelerated by regular tilling? I' know Vavuniya, and at this time of year the area is dry and hot. The rains shouldn't resume until late September or so. If the area was tilled to 8-12 inches every week or so, would that enhance the decay process?

This is an agricultural area, so there should be plenty of equipment available to do the work. Are there any biological supplements (could you inoculate with a digestive bacteria?) or fertilizers that might also accelerate digestion? At this time of year, they might actually make some of Tim's temperatures for a week or a month, too. It's predominantly flat, hot, dry and exposed, or at least it was when I worked there.

Dave Sacco