Anaerobic Digester Volatile Solids Loading
The digester health metric: volatile-solids loading rate VSLR = VS_fed / volume x 1000 (lb VS/day per 1,000 ft^3).
Example
You enter
- Sludge feed flow (gpd) 15000
- Total solids (%) 4
- Volatile fraction of TS (%) 75
- Digester volume (ft³) 20000
You get
- Volatile solids fed 3753 lb/day
- VSLR (per 1,000 ft³) 188 lb VS/day - in the 100-400 healthy band
- Hydraulic detention time 10.0 days
Details, formula, and sources
The VS fed, and the detention time. Overloading past ~400 sours the digester (acid-formers outrun the methane-formers, pH crashes). The loading rate, not a full tank, is the metric; a rich feed can overload at low flow.
VS_fed = feed_gal x 8.34 x (%TS/100) x (%VS/100); VSLR = VS_fed / volume x 1000; DT = volume x 7.48 / feed_gal.
Anaerobic digester volatile-solids loading rate (WEF; university operator courses), by name.
The volatile-solids loading and detention-time relations are public wastewater-operations results; the digester monitoring and the operator govern.
Estimate. AHJ and licensed professional govern.
Field names used by the API: feed_flow_gpd, percent_ts, percent_vs, digester_ft3, vs_fed_lb_day, vslr, dt_days
- High-rate band 100-400 lb VS/day per 1,000 ft^3; over ~400 the digester can sourWEF / operator courses
- Loading is the metric the loading rate, not a full tank, sets digester health; concentration and flow both matterWEF