- Sludge color - darker sludge usually indicates "older" or lower F/M ration sludge. Other factors that can change color include iron sulfides, dyes, etc.
- Sludge density - do the solids have a "fluffy" appearance? Look like gelatin while settling? The way solids form, settle, and compact gives information on filamentous and non-filamentous bulking.
- Settling rates - for a quantitative number, operators read sludge volume every 5 minutes and plat the settling rate. This is important in that rapidly settling sludge (old biomass and low F/M) can settle too quickly leaving "fines" and excess material in the water column.
- Floating solids on top - is it ashy? (old sludge), float up after sitting for a few hours? (denitrification), or have a scum layer (often high fats, oils & grease).
- Supernatant turbidity/color - water turbidity can be a very good indicator of early upset or aging sludge before effluent TSS changes.
Many people run either the SV30 or SVI (just a MLVSS adjusted SV30) and generate a single number that helps operators make decisions on recycle rates, wasting rates, and polymer usage. Today, I am going to introduce other qualitative and quantitative measures that can be taken while running the SV30 test.
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