Evaluating a novel UV device for wastewater disinfection : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Environmental Technology and Sustainable Energy at Massey University, Manawatu Campus, Palmerston North, New Zealand. EMBARGOED until 31 March 2016
UV disinfection is the most common method used in wastewater disinfection. However, some types of wastewater effluent have a low UV transmittance (UVT), which cannot be disinfected efficiently by a commercial UV reactor. A novel UV reactor (called the project prototype) was developed, which has a different type of reactor hydraulics than a typical commercial UV reactor. This change in hydraulics is believed to be an innovative method of improving the low UVT fluid disinfection. The main purpose of this project is to evaluate the feasibility the project prototype.
The settings of the project prototype were first refined, and then compared to a control reactor, which was used to mimic a commercial UV reactor (called the commercial unit) at a range of UV doses. The UV dose was manipulated by changing the number of operated UV lamps and operated flow rate of the reactors. The disinfection performance of the reactors was not only compared at conventional wastewater treatment plants, but also at stabilization ponds. Within the conventional wastewater treatment plants, the reactors were tested using the effluent from the primary, secondary and tertiary treatment stages. In total, the reactors were compared twelve times at seven different wastewater treatment sites.
The results show that the project prototype was, on average, 1.4 times worse than the commercial unit at treating tertiary wastewater, where the wastewater had a high UVT (55 to 65%). This high UVT value favours the use of the commercial unit, as it is designed for this UVT range. However, at a low UVT range, the project prototype performed, on average, 1.4 times better than the commercial unit, at treating secondary wastewater, where the wastewater had UVT of 22 to 55 %. In the stabilization pond tests, where the UVT was 11 to 25%, the project prototype performed 2.1 times better than the commercial unit on average, and up to 8 times better at one location. In the primary treatment test, where the UVT of the wastewater was extremely low (5%), the project prototype, on average, performed 4.5 times better than the commercial unit, and in one case up to 13 times better than the commercial unit.
The research found that the project prototype has an advantage when treating low UVT fluid and great potential in the commercial market. The project prototype performs better
than the commercial unit at stabilization ponds. This suggests that the project prototype would be a viable option for pond treated wastewater disinfection. In addition, the project prototype offers superior performance on primary treated wastewater. This indicates the potential application at marine outfalls (primary treated wastewater), and the possibility of primary wastewater disinfection for irrigation. Overall, this research confirms the feasibility of the novel reactor in wastewater disinfection.