Liquid gold

Times Contributor    

 

With current shortages on fertilizer and rising costs for it, researchers look for other ways to fertilize crops.

Aged manure used as fertilizer is familiar to residents around Strathmore. Another common method used in Southern Alberta is spreading bio solids from waste treatment plants on land. 

“The monitoring shows agronomic rates give good crop response,” said Gordon Dinwoodie, Land Reclamation Specialist with the Alberta Department of Environment and Sustainable Resource Development

Bio solids come from sewer treatment. Solids are removed from sewage by filtration, mixed with oxygen and microorganisms that use anaerobic digestion to break down the organic solids, and neutralizes pathogens still in the wastewater. The water solution filters off and the muck that is left is the bio solid. 

Some of the public concerns with bio solids are bacteria and disease, pharmaceutical residue and offensive odor. Alberta Environment continues to monitor and develop regulations addressing those concerns.

Regulations for heavy metals from industrial waste began in the 1980’s.

“What’s been done over the years is source control. It really cleaned up the heavy metal issue in bio solids and I would say that the heavy metals are not that big of an issue anymore,” said Dinwoodie.

Since that time, Alberta Environment has developed comprehensive regulations dealing with the treatment and spreading of bio solids. Dinwoodie said the recent release of The Canadian Council of Ministers of the Environment report ‘The Guidance document for the beneficial use of municipal bio solids, municipal sludge and treated septage’ www.environment.alberta.ca will encourage jurisdictions to modify regulations even further.

 “Pathogens are always a big concern. The treatment processes they go through, from all the information we have been able to see, are fairly effective at getting rid of those microorganisms,” said Dinwoodie.

However, some studies have shown within a mile radius of spread sites an increased occurrence of staph bacteria causing rashes, other illness and breathing problems. He said Alberta currently doesn’t regulate pathogen limits but limits could be set and testing done.

“A lot of other jurisdictions do that and I would like to move us in that direction. The other approach is operational requirements.  

How the sludge is treated and time it remains in the lagoons,” said Dinwoodie. “There are some pharmaceuticals and personal care products that do wind up in the bio solids. When it gets land-spread, studies show the resulting concentrations are really quite low and once they get into the soil they degrade. There are a few that are fairly persistent. One is tryclosans. They come in things like anti-bacterial soaps. The question for us as regulators is what are the implications of that? A lot of research is going on and the story is not completely written on that yet. Studies show they are not taken up by plants, which is good news. Nobody has identified any problems yet, but more research needs to be done.”

The odor comes from the sulphur and ammonia compounds that are by-products of microbial action at work in the treatment process and after soil application. It is the process that also kills the pathogens. The smell can decrease by mixing in lime and applying heat in the treatment process. In the soil, quick soil tilling or use of direct injection will decrease the odor. 

The process is a green method of providing nutrients to the soil. The spreading is allowed on land that grows small cereal grains, oilseeds, dried legumes, and forage crops, but are not permitted under current provincial guidelines, on root, vegetable, or tobacco crops, or dairy pasturelands.

“Research shows it doesn’t transfer to the foods we eat. Literature doesn’t show any uptake,” said Dinwoodie. “The material is full of nutrients, in my perspective as a soil scientist it is a shame to throw those nutrients away. It is high in phosphorous. That is why we talk about the responsible use of land spreading. It needs to be managed properly and managed properly there are benefits for farmers in terms of organic matter additions and nutrients that can offset fertilizer and costs.”

The bio solids get contracted out to private trucking and application operators, who sign contracts with farmers to apply to their fields. Tests should be done to make sure land is not over saturated. Making sure the operators are applying the product properly is hard to police. 

“We rely on having the rules in place on what they are supposed to do or not supposed to do. If people see them pumping stuff into a ditch or something that should be reported to us they should call the. 1-800 number (1-800 222-6514) for emergency issues or environmental concerns,” said Dinwoodie.