Biosolids don’t stink

To The Eagle:

“Oh my God, it’s pooh!” These were the first words uttered when visiting the Renton wastewater treatment plant (WWTP) for the first time as an engineering student. That reaction is reminiscent of the knee-jerk reaction I’m observing today among Wahkiakum residents. I have studied biosolids a lot since then; and a dear colleague just completed his PhD on the matter. Let me attempt to explain why Class A biosolids should not be included in the County’s proposed ban.

A biosolid itself is the solid material from the clarification process at the WWTP, where liquids are separated from the solids which sink (sludge). The solids go into a digester where bacteria consume them, then excrete a new waste material we call biosolids. If this sounds unpleasant to you, please realize every time you bite into cheese, eat a cured sausage or drink alcohol; you are consuming the waste product of bacteria. We just happen to call these bacteria “yeasts” when they are used in food making.

Biosolids are further chemically ‘incinerated’ with alkaline lime. The extra treatment, increasing the pH to 12, ensures no pathogens survive. Fecal coliforms are not present in biosolids.

Class A biosolids are used widely in agriculture and if you’ve ever eaten produce (meat or vegetable) from say Yakima, Walla Walla or the Skagit Valley it is very possible those fields were fertilized with Class A biosolids. It is safe to apply to fields where animals are grazing and appears now in commercially available fertilizers like you would buy at Home Depot.

By weight, Class A biosolids are roughly 50 percent lime. This is an incredibly important and costly ingredient which our farmers need to rehabilitate our naturally poor, highly acidic soils. To be able to get fertilizer and lime in the form of Class A biosolids has been truly a blessing; rather than having to apply the two separately.

I will not speak to Class B biosolids, except to note that ironically the largest use statewide for these are application to forest lands. Decomposition of wood debris deprives the soil of nitrogen and makes it turn more acidic. The Class B’s provide these lost nutrients and the lime raises the pH balance, making the return on regrowth quicker with healthier soil.

A concern was raised regarding potential pharmaceutical residues in Class A biosolids. Pharmaceutical drugs are metabolized by the kidneys or liver into urine. These are all water soluble and therefore are removed from the system during clarification and therefore do not reach the biosolids.

Another concern was raised regarding heavy metal build-up in soils. The heavy metal worries also concerned me when first contemplating biosolids; however my opinion has entirely changed. Longview WWTP has recently begun producing Class A biosolids, a laudable accomplishment. We sat down with the actual biosolids heavy metal analysis from the treatment plant and then compared the number to the Federal EPA allowable limits.

A bit of quick math showed in order to reach EPA threshold levels for arsenic, one would have to apply Class A biosolids at a rate of 6,732 tons (13,464,000 pounds) per acre or at one ton per acre for 6,372 years. The similar calculation for mercury is 39,473 tons per acre and lead 7,882 tons per acre. It would take impossible conditions or millennia for Class A biosolids to contaminate soils with heavy or trace metals.

By comparison, consider chicken manure which can be applied without restriction to one’s pasture which would reach the same threshold levels in ‘just’ 616 years; a full order of magnitude quicker than Class A biosolids.

If we are to take the stand that “better safe than sorry” on the use of biosolids in Wahkiakum County, then we really ought to follow the logic to its fullest extent. Farming, raising livestock, forestry and industry should all also be banned, as they have all shown to some extent to be harmful to groundwater, surface water, fish or the environment. This is, of course, a ridiculous proposition.

I encourage the County Commissioners to not include Class A biosolids in their proposed ordinance banning biosolids. Please, appeal to reason rather than have that knee-jerk response I once had many years ago.

Loren P. Jennings, PE

Puget Island