NV Water/Wastewater Operator cheat sheet

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.

CT (contact time) value = disinfectant residual concentration (mg/L) x effective contact time (minutes); required CT depends on disinfectant type, water temperature, pH, and target pathogen log inactivation.

Chlorine demand = chlorine dose minus chlorine residual after the contact period; demand must be satisfied before any free residual persists.

Log inactivation removes 10^n of the target organism: 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%; the SWTR requires 3-log Giardia and 4-log virus inactivation for surface water.

Turbidity limits under the IESWTR: combined filter effluent must be <=0.3 NTU in at least 95% of monthly samples and never exceed 1 NTU; conventional filtration requires individual filter effluent <=0.3 NTU in 95% of samples.

Stage 2 DBPR LRAA limits: TTHM 80 ug/L and HAA5 60 ug/L, calculated as locational running annual averages at each monitoring location.

Lead action level is 0.015 mg/L and copper is 1.3 mg/L, evaluated at the 90th percentile of first-draw samples from high-risk sites.

Detention time (hours) = tank or pipe volume (gal) / flow rate (gal/hr); volume of a cylindrical tank = 0.785 x D^2 x H, with D and H in feet giving cubic feet.

Distribution storage must maintain system pressure: 20 psi minimum at all points under normal conditions and 20 psi minimum during main breaks and fire flow; pressures above roughly 100 psi require pressure-reducing valves.

Chlorine residual target: maintain a detectable free chlorine residual throughout distribution, commonly 0.2 mg/L minimum and up to 4.0 mg/L maximum at the consumer's tap under the Stage 2 DBPR.

BOD5 measures oxygen consumed by microorganisms over 5 days at 20 C; typical untreated domestic wastewater is about 200-250 mg/L BOD5 and 200-250 mg/L TSS.

Secondary treatment standards (40 CFR 133): 30-day average effluent BOD5 and TSS of 30 mg/L each, with removal of at least 85% of influent BOD5 and TSS.

F/M ratio = pounds of BOD5 applied per day / pounds of MLSS (or MLVSS) under aeration; low F/M (long MCRT) favors nitrification, high F/M favors rapid BOD removal but poor settling.

MCRT (sludge age, days) = pounds of solids in the aeration basin / pounds of solids wasted plus effluent solids per day; increasing MCRT increases nitrification and reduces sludge production.

SVI (mL/g) = 30-minute settled sludge volume (mL/L) x 1000 / MLSS (mg/L); SVI roughly 80-150 indicates good settling, above about 200 indicates bulking.

Return activated sludge rate is set by the sludge volume index and the desired MLSS; a rising blanket in the secondary clarifier with low RAS flow indicates solids washout risk.

Chlorine disinfection contact time: typical design is 15-30 minutes at peak flow with a residual of 0.5-2.0 mg/L; fecal coliform limits are usually 200 CFU/100 mL monthly geometric mean (or 126 E. coli).

Collection system infiltration/inflow: infiltration enters through defective pipes and joints (groundwater), inflow enters through direct connections such as roof drains and manhole covers; both increase hydraulic loading without increasing organic load.

Anaerobic digester stability: maintain pH 6.8-7.4, alkalinity above roughly 2000 mg/L as CaCO3, and volatile solids destruction of 40-60%; a dropping pH with rising volatile acids signals souring.