SV30 & SVI ~ While the single number is great.... other things can be learned during the test!

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.

• 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.

Again - these tests are best when performed on a frequent basis to obtain standard operating data. Once a system is well known in response to various loadings and environmental changes.