BOD5 - An indirect measurement of the organic matter present in the water. The BOD5 test is done by measuring the amount of dissolved oxygen used by microorganisms like bacteria to consume organic matter in the water over a five day period.
pH - Refers to the hydrogen ion content of a solution; above 7.0 is basic, below is acidic.
Sludge - Solids that settle out of raw wastewater, and solids generated in the treatment processes and are then settled out.
Turbidity - The amount of suspended solids in a body of water or "cloudiness".