Do you know why your UV system is not performing. The lamps need to be changed at the specified hours run. Any lamps out will significantly affect performance. The sleeves need to be cleaned on a three monthly basis (unwiped) or six monthly basis for the wiped system (and you need to ensure the acticlean system is in good working order, every six months). On this basis the sleeves need to be sparkling clean on cleaning to mildly cloudy when cleaning is required. Take the lamps out of the effluent and rinse with potable water and then allow 2 minutes for the water to run off and the sleeves to air dry. Then observe the fouling. I would recommend 5-10 % phosphoric acid solution for cleaning. Perhaps your Trojan rep can troubleshoot the unit for you.

The effluent quality needs to be suitable for UV to work. Beyond 12 mg/L TSS you will find UV ineffective. This usually results from a problem with your activated sludge system (such as insufficent aeration (SVI>250 ml/g) or clarification. You could troubleshoot your A/S plant or look at installing a filter (sand, cloth media) upstream of the UV unit.

The UV transmittance of the effluent is paramount and I would recommend you take some samples and have them analysed by the lab. If the design UVT value is higher than the measured value then  you need to look at having your UV unit resized by your Trojan rep. and then look at further capacity. Things that interfere are colour (numbers greater than 50), TSS (>12 mg/L), COD and iron (> 1.5 mg/L). Colour can be affected by seasonal water supplies with high colour.

For chlorine you need an approriate detention time. A 30 min time at peak hourly dry weather flow is generally required to meet 200 TC per 100 mL. You would need to ensure your outlet residual meets your permit standards. May need dechlorination

 As for ozone, you are looking at a lot more complexity and cost.

 I hope that I have given you some things to think about.

Regards

Grant H, Australia