The E. coli inactivation was conducted under UVA in tubular glass reactor (length of the reactor 100 cm and diameter 4 cm) in continuous mode. The volume of reactor was 10 L and transmittance of treated water at 365 nm was 65%. The power and efficiency of the lamp were 100W and 20%, respectively. The diameter and length of the lamp were 2 cm and 90 cm, correspondently.

Time, min	CFU / 100 mL
0	1.5*10^6
1	3.6*10^5
3	7.5*10^3
5	1.8*10^2
7	1*10^2
9	8

a) Calculate the dose received by water (mWs/cm2) at distance 0,5 cm from the lamp at each sampling point. Plot results of disinfection (CFU/100mL) as a function of dose. Discuss which representation of results is preferable (as a function of dose or as a function of time) when comparison with literature is required.

b) Calculate the dose received by water (mWs/cm2) at distance 0,5 cm from the lamp at each sampling point considering that at each sampling point the transmittance of water at 365 nm is increasing 3%.

c) Disinfected water will be reused for golf field irrigation. According to the law, water for golf field irrigation can contain max 200 UFC/100 mL of E.coli. Estimate the cost of UVA disinfection, considering that water will be used for golf fields. The power of the pump is 20W and cost of 1kWh is 0,1.