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Making Middle Earth water fit for humans

April 20, 2016
The final stage of an upgrade to Waitaki District Council’s water-treatment plant (WTP) using GE ZeeWeed will save $400,000, consume less energy, and produce 25 percent more high-quality drinking water for 14,400 residents in the area, which almost spans the breadth of New Zealand’s south island, north of Dunedin.
The original plant was built in 2007, using membranes from a GE competitor. The upgrade employs ZeeWeed membranes, with two trains each carrying seven ZW1000-R1 racks. The modular ZW1000s can fit into an existing tank design with minimal modifications. The Oamaru upgrade is also ready for extra capacity when needed.

With mayor Gary Kircher set to officiate at a grand re-opening of the WTP on April 18, council contracts engineer for water facilities Michael Goldingham spoke to GEreports as the installation was nearing completion.

This upgrade started for me around January 2015. We were going through a hot summer and our demands were getting pretty high and that’s when we found out that we were sailing pretty close to the wind, with our existing membranes being at the end of their life.

The tender process concluded with GE and ZeeWeed selected for the upgrade.

Physical works started in September 2015 and installing the first treatment train took approximately two weeks to complete. We only started the second treatment train in the first week of April, and we’re finishing it for the April 18 re-opening. I inadvertently shortened the timeframe for GE for the second stage! But they’re working well, not too stressy at the moment … so it’s all good.

/><br /> <br /> <em>The water that will run through the ZeeWeed trains first runs as a river through New Zealand’s postcard landscapes.</em><br /> <br /> The water for Oamaru water supply comes down the Waitaki River, which comes from the Southern Alps of New Zealand, and comes through several power-generating lakes and recreational lakes, down the Waitaki Valley. From there, an irrigation company takes that water and puts it through some races and … we get it delivered to the north end of Oamaru, through an open race. From there we pump it up to an open reservoir, and that’s where the treatment plan gets its water from. So, to all intents and purposes, it’s the Waitaki River.<br /> <br /> <em>The “100% Pure” boast of New Zealand tourism campaigns is a fair call in terms of the country’s breathtaking beauty, but Oamaru’s </em><a href=ZeeWeed membranes have a job ahead to make this water fit to drink.

In water-treatment terms, it is good quality water, but it has its issues. Glacial flour is one issue, and that’s a little bit different from most water sources. It’s a very fine glacial silt. The lakes drop most of it out, but some of comes through. It floats around in the water and it’s very harsh on pumps. The river is prone to flooding and spills, and it comes through dairy areas. So while it’s not high nitrogen, there’s a chance that it could have high nitrogen later on. The main thing is that it’s quite high on organics, so the taste and odour is quite a thing, especially during summer. The water flow is higher then, so that’s when it gathers the silt and the dust. The water temperature goes up as high as 22 degrees Celsius, and the organic loading increases. The algaes start blooming, and that load starts coming on.

Another important aspect is how low the temperature gets. Our water goes down to about 2 degrees, not just the river water but our dam froze over last winter, not completely, but it had ice on it. So the water temperature can get pretty cold, as well. That variability is the challenge for the membranes.

The previous trains, from a GE competitor, were installed in 2007 with a life of seven years. Goldingham and his team wanted the new membranes last longer, and the upgrade project also revealed other areas where the WTP could be improved.

Through good luck and good management, we extended the old trains to eight-and-a-half years, and GE has given us a base life of 10 years for the ZeeWeed.

The whole process has increased our knowledge of the water-treatment plant. We’ve found some things with our existing plant that possibly weren’t right from day dot, so now we’ll fix those things up. We learned those things about the control of the water-treatment plant as we put those new membranes in, and the PLC [programmable logic controller]. This process has helped us identify a few things.

With only two treatment trains, when one’s offline we’re down to half the capacity, so we had to be very careful what time of year that we did this project. That’s where GE helped us out. The first stage was a bit late, but it was still at the right time that we didn’t run out of water. Then we had to wait until after summer to do this second stage. If we’d tried to do this second train after summer, we would have run the town out of water. We couldn’t risk that happening, so we left it until now.

We have been nursing those dying treatment train, in between the two stages of the membrane replacement. For this second and final stage we have to manage the plant and our storage, as we are down to half capacity in the treatment plant, while the second half of the membranes are being replaced. That has a real risk of not being able to supply enough water for the area. We put some water restrictions on in the town, as a risk mitigation … asking people not to water their garden and not to wash their cars. We’ll be more than happy that those restrictions will be lifted on Monday. If this second stage had not gone well, we would have had to continue those restrictions for another week.

/><br /> <br /> <em>The newly-installed trains at the Waitaki District Council’s water-treatment plant.</em><br /> <br /> <em>The council empowered Goldingham and his team to manage the upgrade.</em><br /> <br /> Our exec team let us make decisions, and let us be quite risky in how we ran those old membranes to get that extra life out of them. We had great support from our managers to make good decisions, and that was a really important aspect of the whole upgrade.<br /> <br /> The professionalism of GE has helped in all this, from the initial conversations and that followed right through the project. It’s not that there have been no problems, but any problem we’ve come across, they’ve been solved, professionally.<br /> <br /> <em>Waitaki Council also added GE’s Industrial Internet-driven </em><a href=InSight* Pro Process Consulting Service to the WTP which automatically collects data on water process and quality from the new membrane system and converts it into graphical reports. A GE process specialist is assigned to work with Oamaru to monitor the data and assist the operators with interpreting the results.