Conventional:
BOD = biochemical oxygen demand; measure of organic content
TSS = total suspended solids
Oil and grease
pH - ciritical if nitrified-ww

Nonconventional:
NH3-H = ammonia-nitrogen; represents a nitrogenous oxygen demand; std < 1 to 4 mg/L
P = phosphorus
NO3 + NO2 = nitrate+nitrite
TDS = total dissolved solids
fecal coliform - bacteria
COD, Cr⁺⁶, Organic-N, phenols, TOC, fluoride, manganese, pesticide active ingred.

Actual concentration limits are set by the NPDES permit, negotiated with the state. These should be provided by the Colorado Dept. of Public Health in Sept. Although there are no current limits on annonia, N, or P, it is anticipated that these limits will be added, requiring tertiary treatment for nutrient removal at the plant. Common limits in Europe are: 20 mg/L BOD5, 30 mg/L suspended solids; COD <125 mg/L, Total P = 1 mg/L, Total N = 10 mg/L

Theoretical Oxygen demand (ThOH) = amount of oxygen to convert substance to CO2, H2O

Chemical oxygen demand (COD) = experimentally measured oxidation with dichromate; close to ThOD, but pyridines, ammonia, purines are not oxidized

Biochemical oxygen demand (BOD) = amount of oxygen consumed by bacteria during compound degradation; BOD < ThOD due to C incorporated into biomass

influent municipal WW COD:BOD5 2-2.5; effluent sBOD5 2-3 mg/L, sCOD 40-60 mg/L

Nitrogenous oxygen demand: NH4+ + 2 O2 -> NO3- + H2O + 2 H+

Denitrification by bacteria (in absence of oxygen): nitrate -> nitrite -> N2 (g)

Anaerobic bacterial degradation of organics -> CO2 + CH4 + water (NH3, H2S, mercaptans)

Phosphorus: stored intracellularly in polyphosphate, uptake in aerobic phase

Pretreatment: bar racks, grit chambers, communitors, flow equalization

Primary treatment: primary sedimentation tanks

Secondary Treatment (for carbon removal):

• trickling filter (shallow rock filter, structural plastic, plastic rings in tower)
• activated sludge (CSTR, plug-flow, tapered aeration, contact stabilization; aer or anox)
• oxidation pond or lagoon (aerobic, facultative, anaerobic)
• rotating biological contactor,
• sequencing batch reactor
• secondary settling tank

Disinfection

Advanced WW Treatment (AWT) or Tertiary Treatment (for N, P, toxics removal)
filtration, carbon adsorption, phosphorus removal, nitrogen control, land treatment

Residuals handling: sludge

• thickening by gravity or flotation;
• stabilization through biochemical digestion;
• chemical conditioning;
• dewatering by vacuum, pressure, drying
• chemical reduction: wet oxidation or incineration