• Acids: H⁺  , pH<7 
• Bases: OH^- , pH>7
• Strong acids and bases = complete dissociation 
• Small pKa means slight dissociation (weak acids and bases do not completely dissociate)

• HCl <--> H⁺ + Cl^-

• NaOH <--> Na⁺ + OH^-
• Ca(OH)₂ <--> Ca²⁺ + 2OH^-

1. Ability of a system to resist a change in pH
2. Most common uffer is Carbonic acid system / carbonate system
3. Alkalinity: measure of buffering capacity based on carbonate system. Expressed in terms of calcium carbonate equivalents.

1. Form from anaerobic decomposition of organic matter
2. Immediate precursors of methand
3. Toxic at high concentration in abaerobic digestion

Common VOAs : 

1. formic
2. acetic
3.  propionic
4.  butyric 
5. valeric 
6. isovaleric

• COD - O₂
• N - TN, TKN, nitrates and nitrites, ammonia
• P - phosphates
• VOA - acetic acid
• Alaklinity - CaCO₃