| | Background and objectives | Results | Conclusions and recommendations
Background and Objectives
Treatment of wastewater highly loaded in organic matter, like liquid hog manure, faces two problems. The high levels of nutrients in the wastewater challenge all treatment systems in achieving full removal. The decomposition of organic matter in the water rapidly uses up the water's oxygen content, resulting in objectionable odours as decomposition becomes anaerobic.
The Snowfluent® trials had three questions:
- what degree of treatment is achieved using Snowfluent® to treat liquid hog manure
- how is treatment achieved during snowmaking, in the snow pack and at snowmelt.
- what are the levels of airborne bacteria (bioaerosols) in the air during snowmaking, and do these levels present any health risk to operators and neighbours.
Results
The major benefits of the Snowfluent® technology demonstrated by this pilot test are:
- Odours are noticeably reduced. Odours from the snow pack are much less than from lagoons. There are minimal odours in the meltwater. The solid residue has noticeably less odour than liquid or solid manure. While there are odours in the immediate vicinity during snowmaking, the best snowmaking conditions occurred during the night and during cold weather, times when the public is not outside.
- Snowfluent® significantly reduced the nutrient/contaminant load in the treated runoff water. Biochemical Oxygen Demand (BOD) was reduced from 6524 mg/L in the raw manure to 3360 mg/L in the runoff, almost a 50% reduction in concentration. Total Kjeldahl Nitrogen (TKN) concentration underwent a 61% reduction, from 2431 mg/L in the raw manure to 946 mg/L in the runoff. The total phosphorous (TP) concentration dropped 69% from 425 mg/L to 131 mg/L as it went from raw manure to snowmelt.
- Faecal coliforms experienced a 5-log reduction (or 99.999%), going from 6.71x106 CFU/100mL in the raw manure, to 27 CFU/100mL in the runoff.
- In one treatment, Snowfluent® does not remove enough of the nutrients/contaminants for the meltwater to be released to surface water bodies. However, the meltwater should be suitable for re-use in the barns for manure flushing, or applied to a crop through irrigation. Alternatively, additional treatment in conventional wastewater lagoons may improve the water quality to the point of meeting regulatory limits for surface water discharge.
- Snowfluent® is effective in decanting water from solids for liquid manure systems that do not use straw. The meltwater from the snow pack is not completely treated, but the colour, nutrients, coliforms, and odour are significantly less than from liquid manure. The solid residue has significantly less odour than that of the runoff liquid, and a more concentrated nutrient value than the raw liquid manure.
- An economic comparison of Snowfluent® with conventional spreading and injection methods of manure management finds that it is comparable in cost.
- Snowfluent® appears to fit into a conventional liquid manure management system without significant changes to equipment and layout.
The draw backs of the Snowfluent® technology demonstrated by this pilot test are:
- In this pilot test nearly all of the nitrogen content of the raw manure was removed. Since most of the nitrogen was in the form of water soluble ammonia, this loss is not unexpected. By expanding the surface area of the water by approximately 30,000 times during the snowmaking operation, Snowfluent has a very significant aerosolization component to it's process. Any cost associated with this loss of nitrogen, must be weighed against the benefits of a substantially less odourous method of manure management. There may be options to reduce NH3 losses to the air, and maximize nitrogen retention in the solid residue.
- It only provides winter treatment. Liquid manure that accumulates in the lagoons through the summer will require lagoon covers or alternate forms of odour control to limit odour problems around the lagoons.
Conclusions and Recommendations
Overall, Snowfluent® offers Alberta pork producers significant opportunities to eliminate odour from lagoons and manure spreading. By decanting water from solids, it can reduce manure spreading costs and land requirements. Since Snowfluent is effective in killing micro-organisms, it reduces water requirements by allowing the decanted water to be recycled to the barn for manure flushing. While Snowfluent treatment does represent a loss of crop available nutrients, it also overcomes the major obstacles to expansion faced by Alberta's hog producers, namely odour from lagoon storage and spreading practices, and water contamination from spreading and infiltration.
Two treatment scenarios are possible:
1. For conventional sized operations, Snowfluent® would be used to decant water from solids. Two snowmaking operations, early and late winter, would reduce lagoon storage requirements to six months storage. In a multiple lagoon system, one lagoon could be converted to receiving meltwater from a snow pile built next to the lagoons. The area for snowmaking would be five or six times the lagoon area, on compacted soil with slopes directing drainage to the meltwater lagoon. The solid residue could be hauled for field spreading in conventional semi-solid/solid manure spreading equipment.
2. For large scale operations, a permanent Snowfluent® system with land application on forages may be justified. In this case, the area required for snowmaking is determined by balancing nutrient and salt loads and water volumes with crop uptake estimates and soil chemistry tolerances. Because of the delayed melt, cropping is limited to forages. There is also an issue of groundwater recharge and the quality of the meltwater infiltrating beyond the root zone. Large snow piles may result in snowmelt seepage past the forage crop's root zone.
The pilot test justifies production scale tests to define the best operational processes and confirm the pilot results with different operations in different climatic areas in Alberta. The process would benefit from having scientifically based odour measurements with the Alberta Research Council's odour protocol. |
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