A: Direct Potable Reuse has been in operation in Windhoek, Namibia for more than half a century (since 1968).

A: Since the 1980s, thousands of water reuse projects have been developed around the world, and it is estimated that more than 200 water-recycling schemes are in operation in the European Union.

A: Many states in the USA use direct recycled water

A: Stormwater and wastewater are different and are already treated separately – they have different pipe systems underground. It’s important to understand that stormwater might look cleaner than wastewater but is actually quite dirty. Water from roofs is more likely to be safer and cleaner than water that has run over the roads.

A: Advanced water treatment (including desalination) remove all minerals from water, so some that are important to receive via the water supply need to be added back at the end.

A: Prions can be removed by effective filtration and reverse osmosis. Treating wastewater or seawater to a drinkable standard would require both filtration and reverse osmosis in the advanced water treatment plant.

UF Purification versus Microfiltration, Which Process To Choose For Your Application?

https://www.safewater.org/fact-sheets-1/2017/1/23/ultrafiltrationnanoandro

A: The issue seems to be a political one rather than a scientific one. The Water Services Association of Australia has produced this document about the growing acceptance of recycled water options which might be useful:
https://www.wsaa.asn.au/publication/all-options-table-lessons-journeys-others

A: You cannot tell the difference because the water from all water treatment plants is ‘pH balanced’ to make it safe and taste good.

A: This can be done but it is better to plan for the amount of water needed rather than turning systems on and off. The recycled water systems can continue to be used when dams are full, rather than drawing from them, leaving that water storage for times when demand is higher or there is a drought.

A: Direct treatment for drinking is cheaper to run, because although they make the same water, it takes money to pump around the recycled water into water courses/dams etc.

A: Direct (option 3) = wastewater goes into an advanced water treatment plant and is then pumped into supply

A: Indirect (option 5) = wastewater goes into an advanced wastewater treatment plant then into a lake, river or groundwater storage, then into advanced water treatment, and is then put into supply

A: Water in option 4 is not for drinking. It would be conveyed in different pipes and must be kept separate from drinking water networks.

A: Drinking water must meet very strict guidelines before it is put into supply. These guidelines ensure that the water is safe to drink.

A: Yes – option three at 150 MLD would be enough for drinking and non-drinking. Also note that there are strict quality standards that need to be met whether for drinking or other use (ie. you have to treat wastewater well before you put it into the environment anyway)

A: There are some storage (resilience) benefits of indirect recycling (option 5). With this option, a reservoir (storage) would need to be built.

A: Option 3 doesn’t require a reservoir to be built. With the Rosedale option previously identified, the treated water would need to be pumped uphill to the built storage lake so there is an additional energy requirement to operate that option.

A: Cost: wastewater treatment costs less than desalination

A: Efficiency: waste treatment is a lot more efficient, with higher water volume recovery. Reverse Osmosis is required for both but there is less pressure on the treatment plant for wastewater treatment, because you have to process so much more water with desalination to get the same amount in the end (yield)

A: Purity: Risks are a bit higher with waste treatment because seawater has lower concentration of contaminants.

A: Evaporation systems can be used to reduce the water portion of water-based wastes by converting the water portion to water vapour. This does not contribute to water supply but could reduce the volume of treated water being released to harbours/waterways.

A: Evaporation technologies are sometimes used to treat the waste stream from desalination, thereby recovering salts and other minerals, and reducing/eliminating the discharge of brine, but these processes are currently very expensive. Evaporation ponds are most efficient in the arid or semi-arid areas (that means, not Auckland!).

A: The methods presented represent what is currently possible/practical. The limits of what we might do by 2040 are not known. Nothing is set in stone and nothing has been decided.

A: This is a constant area of research internationally as desalination becomes more widespread as a source of water. If chosen as a way forward, significant investment would be made on how to do this well – protecting people and the environment and improving efficiency.

A: We have asked the Navy – this may be classified information. We are making enquiries and will come back to you.

A: Nothing has been decided yet – the option would have an impact on the site, and this is what the assembly is for

A: Recycled:
If the recycled water source is in the North, there may not be enough volume to shift it south. The shore will still end up with a blend. In Summer it will have more water coming in from the south to blend, while in winter it would provide the majority of the shore water.

For Mangere it will depend on how it’s configured.

A: Desalination:
No particular site has been specified yet. It could be either in the Hauraki Gulf (easier to manage) or out on the West Coast (better for mixing but harder to manage)

If Hauraki it would likely be Rosedale (where our wastewater assets are)

A: Non-potable use would be for organisations and businesses who have need for lower quality water. It is not practical to construct the pipe network necessary to provide non-potable water for general residential use.

A: Even if it were mandated the cost and responsibility of installing rain tanks would be borne by the household. If this were subsidised, the cost of subsidisation would be paid for by the billpayer. The water utility would still need to have capacity to supply the household during dry spells unless the mandated tank size was 2×25,000 litres. Therefore, we still would need another source until everyone had two large rain tanks or are prepared to go without water during a drought. This is why this option is so expensive.

A: It is 15 million litres. This is the possibility for 1/3 of Auckland roof space having tanks attached.

A: Building regulations are set at the national level. Watercare encourages customers to have rain tanks but we know that plumbing them into the house is expensive.

A: Age of house is not critical but it is easier to plan for and install tanks during building. Retrofitting to older homes can be expensive.

A: A few things would be required to make this work:
– Space for tanks
– Metro supply during droughts
– Backflow prevention

A: They can be. This is done in some new developments. However, when the rain tank is empty, toilet flushing water must come from the metropolitan supply. It’s also more expensive than the larger source options (per household) and the cost will be borne by the household, not the water provider.

A: It isn’t different, it’s about how reliable they are in summer and how densely packed our city is. In summer you need space for 2x 25,000 litre tanks to be self-sufficient.