# Blog

# Wahlbergisms

- September 10, 2013
- Posted by: Eric & Patti Wahlberg
- Category: From the Mind of Eric Wahlberg

No Comments

**M****∙****mg/L**: used to cancel mg, L and M (in Mgal) in pounds and pounds/day calculations**Mgal/10**^{6 }**gal**: used to insert M into the pounds and pounds/day calculations when volume or flow is given in units of gal (10^{6}gal = 1,000,000 gal) or other volume units converted to gal**%TS**: (usually in sludge or sludge cake) expressed as lb/100 lb of sludge or cake; for example, primary sludge is given as containing 4.8% TS is expressed as 4.8 lb TS/100 lb sludge; for example, centrifuge cake is given as containing 22% TS is expressed as 22 lb TS/100 lb cake**%VS**: always expressed as lb VS/100 lb of TS; for example, primary sludge is given as containing 76.8% VS is expressed as 76.8 lb VS/100 lb TS (in digester gas calculations, expressed as 76.8 lb VS_{applied}/100 lb TS)**VSR**: given as a percent and expressed as lb of VS destroyed in a digester per 100 lb of VS applied, or fed, to the digester (lb VS_{destroyed}/100 lb VS_{applied}); for example, a VSR of 59.8% is expressed as 59.8 lb VS_{destroyed}/100 lb VS_{applied}**Percent solids recovery (%SR)**: given as a percent and expressed as lb of TS in output from per 100 lb of TS in input to the thickening or dewatering unit; for example, a belt filter press is given as having a %SR of 96.6% is expressed as 96.6 lb TS_{c}(TS in cake, output from the press)/100 lb TS_{s}(TS in sludge feed, input to the press)**Percent CH**_{4 }**(methane)**: in digester gas; expressed as ft^{3}CH_{4}per 100 ft^{3}gas; for example, 66% methane is expressed as 66 ft^{3}CH_{4}/100 ft^{3}gas (this is the only instance in wastewater math where percent is on a volumetric rather than a weight (mass) basis)**Holy grail of pond math-3.069 ac****∙****ft/Mgal**: if ac and Mgal are on opposite sides of the equals sign or on opposite sides of the railroad track, this conversion factor greatly simplifies the math**F/M**: almost always given without units but is**not**unitless; for example, given an F/M ratio of 0.35, it is expressed as 0.35 lb BOD/d∙lb MLVSS**%AI (active ingredient)**: when used in chemical dosing problems, expressed as pounds of AI per 100 pounds of solution(or however the solution is labeled); for example, 0.35% polymer solution is expressed as 0.35 lb/100 lb soln; for example, sodium hypochlorite (hypo) is given as 12.5% chlorine is expressed as 12.5 lb Cl_{2}/100 lb hypo; for example, liquid alum (LA) is given as 49% dry alum (DA) is expressed as 49 lb DA/100 lb LA**Density**: used constantly in wastewater math to convert back and forth between gallons and pounds (density of water, 8.34 lb/gal, most common), but when concentration is given in percent (%), proper labeling is key; for example, 8.34 lb soln/gal soln; for example, 10.0 lb hypo/gal hypo; for example, 6.21 lb AqA (aqueous ammonia)/gal AqA; for example, 11.0 lb liquid alum/gal liquid alum (or, using an abbreviation, 11.0 lb LA/gal LA)**Remember**: no matter what “method” you use in your calculations (using formulas, using algebra, using dimensional analysis (the railroad track)), if we get the same answer,**we are doing it the same way****When using the railroad track, the units tell you what the equation is and they do the algebra for you!**Practice making your drawings and labeling them like we did in class!