- 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.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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