APPENDIX F - SAMPLE CT CALCULATIONS

Transcription

1 APPENDIX F - SAMPLE CT CALCULATIONS 81 f 100

2 EXAMPLE 1 Surce Water - Surface Water The surce water is surface water frm a river. Treatment Requirements Based n surce water cnditins, the treatment requirements are set at: 3.0-lg reductin fr Cryptspridium and Giardia; 4.0-lg reductin fr viruses. Filtratin Credits (Lg Remval) The treatment facility is a direct filtratin plant. Individual filter effluent turbidity was reviewed and meets the limits f 0.2 NTU 95% f the time. Therefre, this facility receives the fllwing filtratin credits twards meeting the treatment requirements: 2.5-lg reductin fr Cryptspridium; 2.5-lg reductin fr Giardia; 1.0-lg reductin fr viruses. Based n the abve, lg inactivatin (disinfectin) must prvide the fllwing lg reductin: Cryptspridium: 3.0-lg reductin required Subtract 2.5-lg filtratin credit Equals 0.5-lg inactivatin credit needed Giardia 3.0-lg reductin required Subtract 2.5-lg filtratin credit Equals 0.5-lg inactivatin credit needed Viruses 4.0-lg reductin required Subtract 1.0-lg filtratin credit Equals 3.0-lg inactivatin credit needed Treatment Deficiency #1 Because this facility has a shrtfall in lg remval credits fr Cryptspridium, an alternate disinfectant such as UV, chlrine dixide r zne will be required t meet treatment requirements. 82 f 100

3 In this example, UV is selected. The UV unit must be able t prvide a minimum dse f 2 40 mj/cm. This is sufficient t receive a 4-lg inactivatin credit fr Cryptspridium and Giardia (see IT tables in Appendix D) which meets the abve shrtfalls. UV is nly assigned a 0.5-lg inactivatin credit fr viruses. As such, 2.5-lg inactivatin is required by chlrine. Disinfectin Credits (Lg Inactivatin) The cntact chamber has the fllwing cnfiguratin: Directin f flw Cntact Chamber Specificatins: Vlume: 270 cubic metres Max. Flw: 4.1 MLD Dimensins: 9.1 m x 10 m x 3 m Baffling: Single Baffle Min. Temperature: 5 C Highest ph: 7.6 This facility uses free chlrine fr primary disinfectin. In the winter, the fac i lity has a minimum f 1.0 mg/l free chlrine residual leaving the cntact chamber. Based n the cnfiguratin f the cntact chamber the length t width rati is 2:1, which is pr. A baffling factr f 0.3 can be used. Tank lw level ccurs when the tank is 70% full. CT Calculatin Vlume f chamber: 270 cubic metres = L = 0.27 ML x 0.7 (lw level) = ML Cntact time actual: Vlume Max. Flw = ML 4.1 MLD = days x 24 hurs per day x 60 minutes per hur = 66.4 minutes CT actual: Cncentratin f disinfectant x cntact time x baffling factr = 1.0 mg/l x 66.4 minutes x 0.3 = 19.9 mg.min/l CT required (Giardia): UV disinfectin is prviding 4.0-lg inactivatin fr Cryptspridium and Giardia. 83 f 100

4 Adequate fr 0.5-lg Giardia? Yes CT required (Viruses): Referring t the CT tables in Appendix D, 8 mg.min/l prvides 4.0-lg inactivatin f viruses at 5 C, ph 6-9 Adequate fr CT actual CT required = = 2.49 (greater than 1) viruses? Therefre adequate Cnclusin This facility will require the installatin f an alternate disinfectant, in this example UV, t prvide sufficient disinfectin fr Cryptspridium and Giardia inactivatin. Chemical disinfectin will als be required t prvide adequate disinfectin fr virus inactivatin. 84 f 100

5 EXAMPLE 2 Surce Water - Surface Water The surce water is surface water frm a lake. Treatment Requirements Based n surce water cnditins, the treatment requirements are set at: 3.0-lg reductin fr Cryptspridium and Giardia; 4.0-lg reductin fr viruses. Filtratin Credits (Lg Remval) The treatment facility is a cnventinal filtratin plant. Individual filter effluent turbidity was reviewed and meets the limits f 0.2 NTU 95% f the time. Therefre, this facility receives the fllwing filtratin credits twards meeting the treatment requirements: 3.0-lg reductin fr Cryptspridium; 3.0-lg reductin fr Giardia; 2.0-lg reductin fr viruses. Based n the abve, lg inactivatin (disinfectin) must prvide the fllwing lg reductin: Cryptspridium: 3.0-lg reductin required Subtract 3.0-lg filtratin credit Equals 0.0-lg inactivatin credit needed Giardia 3.0-lg reductin required Subtract 3.0-lg filtratin credit Equals 0.0-lg inactivatin credit needed Viruses 4.0-lg reductin required Subtract 2.0-lg filtratin credit Equals 2.0-lg inactivatin credit needed There is n shrtfall in lg remval credits fr Cryptspridium in this example. 85 f 100

6 Disinfectin Credits (Lg Inactivatin) The cntact chamber has the fllwing cnfiguratin: Directin f flw Cntact Chamber Specificatins: Vlume: 303 cubic metres Max. Flw: 3.1 MLD Dimensins: 5.1 m x 20 m x 3 m Baffling: Five Baffles Min. Temperature: 7 C Highest ph: 7.3 This facility uses free chlrine fr primary disinfectin. In the winter, the fac i l ity has a minimum f 0.4 mg/l free chlrine residual leaving the cntact chamber. Based n the cnfiguratin f the cntact chamber the length t width rati is 4:1, and multiple baffles, which is gd. A baffling factr f 0.7 can be used. Tank lw level ccurs when the tank is 85% full. CT Calculatin Vlume f chamber: 303 cubic metres = L = ML x 0.85 (lw level) = ML Cntact time actual: Vlume Max. Flw = ML 3.1 MLD = days x 24 hurs per day x 60 minutes per hur = minutes CT actual: Cncentratin f disinfectant x cntact time x baffling factr = 0.4 mg/l x minutes x 0.7 = f 100

7 Adequate fr Referring t CT Tables in Appendix D: 0.5-lg Giardia? CT at 5 C and ph 7.0 = 23 CT at 5 C and ph 7.5 = 28 CT at 10 C and ph 7.0 = 18 CT at 10 C and ph 7.5 = 21 Therefre: CT at 7 C and ph 7.3 = 21.6 mg.min/l CT actual CT required = = 1.55 (greater than 1) Therefre adequate CT required (Viruses): Referring t CT tables in Appendix D, 7.2 mg.min/l prvides 4.0- lg inactivatin f viruses Adequate fr CT actual CT required = = 4.65 (greater than 1) viruses? Therefre adequate Cnclusin This facility adequately remves and inactivates Cryptspridium, Giardia and viruses and meets Nva Sctia s Drinking Water Treatment Standards. 87 f 100

8 EXAMPLE 3 Surce Water - High Risk GUDI Surce This example demnstrates the requirements fr grundwater under the direct influence f surface water. The results frm the GUDI prtcl indicate that the drilled wells serving the facility have been classified as high risk GUDI. This classificatin has been accepted in writing by the NSE reginal hydrgelgist. Treatment Requirements Since the facility has been classified as high risk GUDI, the facility requires engineered filtratin fr pathgen reductin. The treatment requirements fr this facility are: 3 - Lg reductin fr Cryptspridium and Giardia; 4 - Lg reductin fr viruses. Filtratin Credits (Lg Remval) The facility has a micr-filtratin (MF) membrane system with pre-cagulatin. Individual filter effluent turbidity was reviewed and meets the limits f 0.1 NTU 99% f the time. Direct integrity testing indicates that the membrane prvides 3.14-lg remval fr prtza (e.g. Cryptspridium cysts and Giardia cysts). The system receives n credits fr the remval fr viruses. Therefre, this facility receives the fllwing filtratin credits twards meeting the treatment requirements: 3.14-lg reductin fr Cryptspridium; 3.14-lg reductin fr Giardia; 0.0-lg reductin fr viruses. Based n the abve, lg inactivatin must prvide the fllwing lg reductin: Cryptspridium: 3.00-lg reductin required Subtract 3.14-lg filtratin credit Equals 0.0-lg inactivatin credit needed Giardia 3.00-lg reductin required Subtract 3.14-lg filtratin credit Equals 0.0-lg inactivatin credit needed Viruses 4.0-lg reductin required Subtract 0.0-lg filtratin credit Equals 4.0-lg inactivatin credit needed There is n shrtfall in lg remval credits fr Cryptspridium in this example. 88 f 100

9 The cntact chamber has the fllwing cnfiguratin: Cntact Chamber Specificatins: Vlume: 750 cubic metres Max. Flw: 12.5 MLD Dimensins: 5.1 m x 20 m x 3 m Baffling: n baffles, inlet at tp f basin, utlet at bttm f basin Min. Temperature: 5 C Highest ph: 7.5 The facility uses free chlrine. In the winter, the facility has a minimum f 1.2 mg/ L free chlrine leaving the cntact chamber. Based n the cnfiguratin f the cntact chamber, there is n baffling with pr mixing. A baffling factr f 0.1 can be used. Tank lw level ccurs when the tank is 85% full. CT Calculatin Vlume f chamber: 750 cubic metres = L = ML x 0.85 (lw level) = ML Cntact time actual: Vlume Max. Flw = ML 12.5 MLD = days x 24 hurs per day x 60 minutes per hur = 73.4 minutes CT actual: Cncentratin f disinfectant x cntact time x baffling factr = 1.2 mg/l x 73.4 minutes x 0.1 = 8.81 mg.min/l CT required (Giardia): Referring t the CT tables in Appendix D, fr 0.5-lg inactivatin f Giardia at 5 C and ph 7.5, CT = 28 mg.min/l Adequate fr CT actual CT required = = 0.31 (less than 1) 0.5-lg Giardia? Therefre nt adequate 89 f 100

10 CT required (Viruses): Referring t the CT tables in Appendix D, 8 mg.min/l prvides 4.0-lg inactivatin f viruses at 5 C, ph 6-9 Adequate fr CT actual CT required = = 1.1 (greater than 1) viruses? Therefre adequate Cnclusin The current cnfiguratin f the cntact chamber is nt sufficient t prvide 0.5-lg inactivatin fr Giardia. The cntact chamber can be increased in size, the baffling imprved, the chlrine residual increased t 4.0 mg/l r UV disinfectin can be added. 90 f 100

11 EXAMPLE 4 Surce Water - Medium Risk GUDI Surce This example demnstrates the requirements fr grundwater under the direct influence f surface water. The results frm the GUDI prtcl indicate that the drilled wells serving the facility have been classified as medium risk GUDI. This classificatin has been accepted in writing by the NSE reginal hydrgelgist. Treatment Requirements Since the facility has been classified as a medium risk GUDI, the treatment requirements fr this facility are: 3 - Lg reductin fr Cryptspridium and Giardia; 4 - Lg reductin fr viruses. Filtratin Credits (Lg Remval) A medium risk GUDI facility is eligible fr a 1.0-lg natural filtratin credit fr prtza if the Guidelines fr the Determinatin f Natural Filtratin Lg Remval fr Prtza are fllwed (see Appendix B) and the NSE reginal hydrgelgist accepts the determinatin in writing. This prcess has been cmpleted and accepted by NSE. Therefre, this facility receives the fllwing filtratin credits twards meeting the treatment requirements: 1.0-lg reductin fr Cryptspridium; 1.0-lg reductin fr Giardia; 0.0-lg reductin fr viruses. Based n the abve, lg inactivatin must prvide the fllwing lg reductin: Cryptspridium: 3.0-lg reductin required Subtract 1.0-lg filtratin credit Equals 2.0-lg inactivatin credit needed Giardia 3.0-lg reductin required Subtract 1.0-lg filtratin credit Equals 2.0-lg inactivatin credit needed Viruses 4.0-lg reductin required Subtract 0.0-lg filtratin credit Equals 4.0-lg inactivatin credit needed 91 f 100

12 Treatment Deficiency #1 Because this facility has a shrtfall in lg remval credits fr Cryptspridium, an alternate disinfectant such as UV, chlrine dixide r zne will be required t meet treatment requirements. In this example, UV is selected. The UV unit must be able t prvide a minimum dse f 2 40 mj/cm. This is sufficient t receive a 4-lg inactivatin credit fr Cryptspridium and Giardia (see IT tables in Appendix D) which meets the abve shrtfalls. UV is nly assigned a 0.5-lg inactivatin credit fr viruses. As such, 3.5-lg inactivatin fr viruses must be addressed. In this example, chlrine is selected t inactivate viruses. Disinfectin Credits (Lg Inactivatin) The cntact chamber has the fllwing cnfiguratin: Directin f flw Cntact Chamber Specificatins: Vlume: 450 cubic metres Max. Flw: 4.5 MLD Dimensins: 5 m x 30 m x 3 m Baffling: Five Baffles Min. Temperature: 10 C Highest ph: 7.5 The facility uses free chlrine fr virus disinfectin. The facility has a minimum f 0.5 mg/l free chlrine residual leaving the cntact chamber. Based n the cnfiguratin f the cntact chamber the length t width rati is 4:1, and multiple baffles, which is gd. A baffling factr f 0.7 can be used. The tank is cnfigured such that it is always full (e.g. utlet weir cntrls water level). 92 f 100

13 CT Calculatin Vlume f chamber: 450 cubic metres = L = ML x 1 (lw level) = ML Cntact time actual: Vlume Max. Flw = ML 4.5 MLD = 0.1 days x 24 hurs per day x 60 minutes per hur = 144 minutes CT actual: Cncentratin f disinfectant x cntact time x baffling factr = 0.5 mg/l x 144 minutes x 0.7 = 50.4 CT required (Giardia): UV disinfectin is prviding 4.0-lg inactivatin fr Cryptspridium and Giardia. Adequate fr 0.5-lg Giardia? Yes CT required (Viruses): Referring t the CT tables in Appendix D, 6 mg min/l prvides 4.0- lg inactivatin f viruses at 10 C, ph 6-9 Adequate fr CT actual CT required = = 8.4 (greater than 1) viruses? Therefre adequate Cnclusin This facility will require the installatin f an alternate disinfectant, in this example UV, t prvide sufficient disinfectin fr Cryptspridium and Giardia inactivatin. Chemical disinfectin will als be required t prvide adequate disinfectin fr virus inactivatin. 93 f 100

14 EXAMPLE 5 Surce Water - Nn-GUDI This example demnstrates the requirements fr a nn-gudi surce. The results frm the GUDI prtcl indicate that the drilled wells serving the facility have been classified as nn- GUDI. This classificatin has been accepted in writing by the NSE reginal hydrgelgist. Treatment Requirements Since the facility has been classified as nn-gudi, the treatment requirements fr this facility are: 4 - Lg reductin fr viruses. Treatment Adequacy A nn-gudi facility des nt require engineered filtratin fr pathgen reductin. Therefre, nly disinfectin is required fr the 4-lg inactivatin f viruses. The utility has tw chices fr primary disinfectin: chemical disinfectin nly r UV and chemical disinfectin. The facility well field is lcated 2.1 km frm the first custmer with a 12 ductile irn water main, which prvides plug flw. The baffling factr fr the water main is 1. The maximum flw in the system is 3.8 MLD. 0 The minimum water temperature is 5 C. With chemical disinfectin nly the utility ensures that the minimum free chlrine cncentratin at the first custmer is 0.4 mg/l. This facility is cnsidering UV as an added barrier fr disinfectin, but wanted t cmpare the tw chices befre making the final selectin. Optin 1: Chemical disinfectin nly Vlume f the chamber = Length f water main x crss-sectinal area = 2100 m x sq. m = 153 cu. m = ML Cntact time actual = Vlume/Max. Flw = ML /4.5 MLD = days x 24 hurs per day x 60 minutes per hur = 49.0 min CT actual = Cncentratin f disinfectant x cntact time x baffling factr 94 f 100

15 CT actual = 0.4 mg / L x 49.0 min x 1.0 CT actual = 19.6 mg min/l CT required (viruses): Referring t CT Tables in Appendix D, 8 mg min/l prvides 4.0-lg 0 inactivatin at 5 C, ph 6-9 Adequate fr CT= CT actual CT required = = 2.45 (greater than 1) viruses? Therefre adequate Optin 2: UV with chemical disinfectin UV will nly prvide 0.5-lg inactivatin fr viruses s chemical disinfectin will be required fr 3.5-lg inactivatin f viruses. Given that the chemical disinfectin wuld prvide mst f the inactivatin the utility reduced the free chlrine cncentratin t 0.3 mg /L as a cst saving measure. CT actual = Cncentratin f disinfectant x cntact time x baffling factr CT actual = 0.3 mg/l x 49.0 min x 1.0 CT actual = 14.7 mg-min/l CT = CT CT = = 1.84 (greater than 1) actual required Adequate fr viruses? Therefre adequate. Cnclusin Bth ptins are sufficient fr disinfectin. Since the facility nly btains a 0.5-lg reductin credit fr viruses fr the UV unit, the utility must evaluate the additinal capital and perating csts f the UV unit, reduced cst f chlrine additin and risk benefit. 95 f 100