この研究では、処理された都市排水からさまざまなコリファージを分離しました。 コリファージは大腸菌に感染するウイルスであり、消毒研究におけるヒト腸内ウイルスのモデルとして使用できます。 分離されたコリファージのほぼ半分は塩素またはUV放射に対して非常に耐性があり、これが塩素またはUV放射だけではすべてのコリファージに対して効果がなかった理由です。
"This highlights the importance of a combined treatment," says Doctoral Student Alyaa Zyara, MSc, from the University of Eastern Finland, who presented the results in her doctoral dissertation.
コリファージが最初に低塩素濃度（{{0}}。1または0.5 mg Cl / L）に10分間さらされた後、低UV放射（わずか22 mWs / cm2）にさらされたとき、研究されたすべてのコリファージは不活化されました。 ただし、処理の順序を逆にすると（UVが最初、塩素が2番目）、消毒の効果ははるかに低くなります。
"It is more effective to first use a low dosage of chlorine followed by a low dosage of UV radiation than to use high chlorine or UV dosages alone. The order of treatment is also important: using UV radiation first and chlorine second was less effective. In other words, the combination treatment using chlorine first and UV second can be recommended as a disinfection method for viruses."
The study also tested novel UV-LED technology, as UV-LEDs are a new method for disinfecting drinking water. The study used UV-LEDs operating at a wavelength of 270 nm and with a 120 mW irradiation capacity, which haven't been used in disinfection studies before. As little as 2 minutes of this UV-LED treatment was enough to cause a 90-99.9 percent reduction in the coliphages tested in a 5.2-litre reactor. Irradiation time of 10 minutes in the same reactor increased the reductions to 99.99 -- 99.999 percent . A traditional mercury UV lamp at a 254 nm wavelength caused similar or slightly higher reductions in 2 or 10 minutes, but the water volume was only 10 millilitres.
"UV-LEDs are a promising method for disinfecting water, since they consume less energy than traditional mercury UV lamps. Furthermore, as UV-LEDs do not contain any mercury, they are safer for the environment."
The findings were originally reported in Journal of Water and Health, and Water.
