In this interactive solve several situations as a wastewater process engineer.

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Rights: The University of Waikato Published 28 June 2016

The last stage of wastewater treatment disinfects the effluent by zapping the remaining microorganisms and viruses with a dose of UVC. Four situations are presented in this interactive and the aim is to make the correct adjustments to keep the zapping dose high.

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You are a process engineer at a small wastewater treatment plant in New Zealand. The wastewater treatment plant is responsible for releasing clean treated water into the local harbor for recreational activities.

It is your job to ensure that the treated water released into the harbor is safe for the people of the township to enjoy.

Let’s take a look at your wastewater treatment plant.

This is your wastewater treatment plant. You will be in charge of the tertiary treatment section where the wastewater is disinfected. We will present you with four problems to solve.

Learn about the disinfection process.

Tertiary treatment

The UV plant is basically getting effluent from the secondary treatment process. So you have the secondary treatment process carry suspended solids, it basically forms a film on the lamps itself. So there’s a sleeve which goes across and is cleaning the lamps to have optimum rays coming out. The plant is monitored everyday. We are trying to target a certain dose, at which we know that the microbial organisms are dead, and the other thing that we do is monitor the UV intensity, and if the intensity starts falling below a certain level we replace the lamps. And this happens after 12,000 hours of working. We tend to not replace them every day but we tend to replace the entire channel every so often. When a channel is in service we know the run hours, so what are we monitoring for maintenance purposes would be the run hours on the channel, uh, that’s the classic indication of how long will it last and what do we need to do to bring it back online. We clean the channels as well, along with the wiping system there’s a physical process of hosing the channels off, hosing the lamps off to keep it clean.

Continue to monitoring station

This is your monitoring station where you can see these following things:

  • Intensity of the UV lamps in the wastewater disinfection channel.
  • Number of run hours the lamps have been shining for.
  • Flow rate of the wastewater entering the channel.
  • Time since the lamps were last cleaned.

It is your job to make sure that the harbor receives clean treated wastewater and that your disinfection section operates within a set budget. Be careful! Replacing the UV lamps is very costly and should be done only when you really have to.