= 70 1.6 = 112 mg/L-min

= 10 1 = 10 mg/L-min

By interpolation of table C99.9% = 12.2mg/L-min, 34.8mg/L-min Ratio CT/CT99%: For clearwell = 112/12.2 =9.2 For pipe =10/34.8 =0.29

Total CT/CT99%= 9.2 + 0.29 =9.5 Therefore Giardia log inactivation = 3log (CT/CT99% = 39.5 log = 28.5 log

6. The Ct concept is used to calculate how much disinfectant is required to adequately disinfect water that is a measurement of disinfectant efficiency. The Ct concept involves the determination of the achieved contact time between the disinfectant and microorganism and the concentration of disinfectant. Ct refers to the final residual concentration of a particular chemical disinfectant in mg/L and t refers to the minimum contact time (minutes) of material that is disinfected with the disinfectant i.e. CT = disinfectant concentration x contact time = C mg/L x T minutes Therefore, the units of CT are expressed in mg-min/L. The Ct value is dependent on factors such as pH, temperature, strength of disinfectants and microorganism compared with required CT values from developed tables (e.g. the achieved CT value can compared with the standard table for 99% removal of Giardia lambia)

7. Indicator organisms to test the effectiveness of effluent disinfection in a wastewater treatment plant. Indicator organisms live under the same conditions that human pathogens live. Tests for easily detectable indicator organisms are conducted and the assumption is that if we kill the indicator organisms then we most likely kill the pathogens during effluent disinfection. The inactivation rate (organism killed/ volume-time), is proportional to the concentration of viable organism, N that is dN/dt =-KN Indicators include coliforms that come from the same sources as pathogenic organisms. Coliforms are relatively easy to identify, are usually present in larger numbers than more dangerous pathogens, and respond to the environment, wastewater treatment, and water treatment similarly to many pathogens. As a result, testing for coliform bacteria can be a reasonable indication of whether other pathogenic bacteria are present. Cryptosporidium is resistant to chlorination; however Ozonation and disinfection with ultraviolet light are effective in destroying Cryptosporidium.