1 Mar 2010

Is there a risk using sewage sludge in farming?

Blog readers may remember Panorama's programme about sewage - see my blog here - well a few weeks ago I was at the Wessex Water Customer Liaison panel on behalf of Stroud District Council - the next post will cover that meeting but here I wanted to talk about sewage more.....here is a rather hasty discussion...

Photo: Inside the WW building - great cafe for meeting - acclaimed as a good design for people to work in...

One of the questions I asked related to the use of sewage sludge - in the US there is much concern from some Organic campaigning organisations:

That link leads to a number of US articles that raise questions about the safety of the use of sewage sludge in agriculture. I asked how the British use of sludge varies from the US and what WW make regarding the allegations that effectively say this sludge is a hazardous waste renamed as "organic fertilizer" (or "biosolids")?

One of the article reads: "Household sewage, contaminated as it is with chemical cosmetics, toxic household cleaners and any number of pharmaceutical drugs poured into toilets and kitchen sinks, isn't pristine; but, to paraphrase Bob Hope, it's not the shit, it's what we've done to it. After the toilet is flushed or the drain is emptied, household waste is funneled into a vast underground sewage system, where it joins a toxic stew of industrial and hospital wastes and rainwater runoff from our streets and highways. Allowing corporations to flood the environment and the waste stream with 100,000 synthetic, mostly toxic chemicals, (most of which end up in sewage sludge), less than 1% of which have ever been proved to be safe for the environment and public health, is a form of insanity. Besides contaminating the water and soil, this irrational so-called "sewage treatment" process wastes enormous amounts of potable water..."

"Human and animal manure, (separated from and free from chemical and pharmaceutical residues), throughout the centuries, and in the present time can and should be safely composted and utilized as a fertilizer on fields, farms, and forests. Although current organic standards prohibit the use of compost derived from human manure (properly composted animal manure is allowed) on food crops, feeding the soil with properly composted "humanure" (or producing methane gas for energy use through bio-digesters) will no doubt become the norm in the future as fossil fuel and water supplies dwindle and chemical fertilizer costs become prohibitive."

I had a detailed response which I can't cover here in full but suggested the articles are an unfortunate miss use of information and overstating of the problem. There are apparently differences between US and European legislation but WW note that the facts do not support the views expressed in these papers, which use very excitable language unusual for scientific papers. Indeed they do, but I still think there is good reason to be concerned....

I was pleased therefore that WW noted that the concerns raised about the use of chemicals in the home and the environment are legitimate and have been considered for a long time.

In the UK we have a range of legislation that deals with the use of chemicals and which chemicals can be used without harm once they are disposed of. We have whats called 'a safe sludge matrix' that monitors the quality of sludge that can be put to land and have for many years monitored the levels of metals in sludges intended for use as fertiliser to ensure that no toxicity emerges.

Legislation for the use of such chemicals continues to evolve and there are a number of new or updated pieces of legislation dealing with chemicals and their disposal either being implemented or about to be implemented. There is no evidence of acute toxicity but work continues to understand the effects of pharmaceuticals disposed of and particularly their daughter compounds as well as the effects of other organic compounds such as endocrins. Indeed I was pleased to hear that WW are specifically looking into this area with their own research.

I would appreciate other's thoughts on this.


Anonymous said...

Interesting blog item. I operate a business in the organics industry. I come across a variety of organic waste applications and quantities and types of land. There has been some extensive research going on into the application of quality products to agricultural land and I am pleased to say that quality composts look favourable at this early stage. The significant difference here is that these are products that are coming from source segregated material streams and are processed through a thorough process, I do not think that all sewage sludges are recovered to such standards.

However, I am not totally against the use of sewage sludge in agriculture if we consider the benefits of sewage sludge. It provides organic matter retaining moisture. Therefore require less watering of water hungry plants. High in nutrients, particularly Phosphorous. With nutrients in mind I suppose it is an alternative to using the bagged artificial fertilisers extracted and produced at great energy and unsustainably. (I acknowledge that a fair proportion of the fertiliser value actually comes from industry and domestic use of products derived from usustainable sources also).

I think the use of sewage sludge is not the problem it is more what goes into the sewage itself. Perhaps some feasibility work could be done into segregating sewage into 'cleaner' feedstocks and 'dirtier' feedstocks so that the quality of sewage sludge could be improved and applied in a safer and more sustainable way. Turning sewage sludge into a better and more sustainable asset.

We are fast moving away from putting all our waste into a bin that goes to landfill and separating this out into useful resources and new products. Perhaps we should be moving more quickly towards washing all our products down one sewage system that goes to one sewage process?

Anonymous said...

Agree with the last comment - segregate our sewage on all new build as a start and at the very least insist on segregation of rain water - it is crazy that a lot of that still goes into sewage system. Reed beds where possible and land available. Maybe even composting toilets?

Jim bynum said...

Chemicals are long term hazards associated with sludge use. It is well to discuss them, except the authorities can not afford to test for them or tell you how many cause cancer. The real danger is from disease organisms for which there is no economical way to remove from sludge. Few people understand that treatment of sewage consists of bacteria decomposing the fecal organics in the waste stream. Authorities will assure you that scientists have established a safe level of fecal coliform (in the U.S. it is 1,000 CFU) in sludge which will not harm animals or humans as they are only indicators that pathogens might be present. What the authorities do not want you to know is that CFU means the laboratory technician actually counted 1,000 colonies of thermotolerant E. coli at the end of the test. Each colony of E. coli may contain millions of bacteria. The high heat of the test suppresses the growth of most bacteria except a few E. coli while the bacteria in sludge keep growing at a normal rate. English doctors have documented E. coli causing the deaths of women and infants in hospitals since 1900.

When sludge was dumped in the ocean farmers had very little Salmonella and no E. coli 0157. Nice scam for a cheap method of disposal.