PRI-DE™ Digester Sulfide and Struvite Control
Example 3. Digester H2S and struvite control
When applied to primary settled solids (prior to thickening/digestion), the effect of the PRI technology is two-fold:
- 1) To remove dissolved sulfide that either contributes to immediate biogas H2S levels or provides a sink for Fe added subsequently; and
- 2) To remove total sulfide and so ‘free up' the iron bound as FeS. That ‘freed up' Fe is then available to control H2S production and/or struvite scaling within the digester.
Example 4. Phosphorus binding into dewatering cakes
When applied to digester effluent prior to dewatering, PRI-Tech frees up Fe2+ from FeS (and oxidizes Fe2+ to Fe3+) with the effect being to partition more phosphorus into the dewatered cake. Side benefits include improved dewatering efficiency, reduced struvite scaling, and enhanced odor control. By capturing more phosphorus into the solids cake, less is returned to the plant influent and so plant-wide phosphorus loadings are lowered - in some cases enough to meet tighter effluent nutrient limits. Phosphorus loadings in dewatering sidestreams can be several hundred mg/L and comprise 25-50% of the total plant phosphorus loading.
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