reyoz's comments

RO does use a lot of energy to overcome the osmotic pressure and to create flux through the membrane. An interesting concept is using the reverse process, "forward" osmosis, to extract the energy where fresh water mixes with seawater, such as a river mouth. This is called pressure-retarded osmosis (PRO) and was tried at pilot scale by Norwegian power company Statkraft. Ultimately this trial was shelved due to being uncommercial [1], perhaps future membrane development will improve the viability of FO. And yes the membranes are quite different, RO membranes are relatively thick due to the transmembrane pressures required. FO requires a much thinner support for the active layer as there is no external pressure applied to push the water through (it is drawn through by the difference in salt concentration).

[1] https://www.powermag.com/statkraft-shelves-osmotic-power-pro...

Having a diversity of water supplies and using water fit for purpose reduces demand for drinking water. Toilet flushing, irrigation and even washing machines do not need high quality drinking water. I have 5,000L of rainwater storage that I use for toilet flushing and irrigation. Combined with a water efficient shower head (typically the largest domestic water use in my country) we use 100 L/d/person. In some areas of my city there is dual supply plumbing that delivers highly treated wastewater for these uses.

For a short backstory on Wittenoom, an former asbestos mining town in remote Western Australia see this video https://www.youtube.com/watch?v=q3LDoI7H1Gc

I once worked with an environmental engineer who had a grandfather that worked at Wittenoom. He passed away due to mesothelioma, but her father who grew up there has not been affected, which is quite amazing given the circumstances. I have seen footage from Wittenoom of children playing in mounds of asbestos.

Today there are two general types of legacy asbestos products, friable and non-friable. Generally non-friable products such as asbestos-cement sheeting are considered safe to leave in place and are only dangerous when cut, broken or otherwise damaged. Friable products such as pipe lagging are very dangerous as they easily break down into fibers that can be inhaled.

It can be found in many old homes in odd places. I was removing some old putty around a window and a friend of mine who was an asbestos hygienist suggested that it could contain asbestos and took a sample for testing (all clear thankfully).

In another instance I worked on a demolition of a 1960's era multistory apartment complex. During construction of the concrete core walls the builder had used asbestos in the formwork, leaving some embedded in the wall at regular intervals. This meant that all of demolition waste was considered contaminated and was going to a special dump at a huge cost.

Finally, there was an infamous case in Canberra, Australia where a company called Mr Fluffy [1] installed loose friable asbestos as insulation in homes. A cleanup program in the 90's did not adequately fix the problem and so in 2014 the government finally purchased affected properties and demolished the houses.

Asbestos is bad stuff, but exposure causing mesothelioma seems to be a bit like Russian roulette. You might get it, you might not. But if you do, you will die.

[1] https://en.wikipedia.org/wiki/Mr_Fluffy

A recent report [1] looked at the efficiencies of generating hydrogen at a waste water treatment plant to lower production costs. The WWTP provides the water and uses the oxygen that is also produced by electrolysis to increase the efficiency of the biological treatment process vs air. Some of the electricity for the electrolysis can also be sourced from biogas produced by the WWTP.

[1] https://www.jacobs.com/sites/default/files/2020-06/jacobs-ya...

I put in a Sanden heat pump to replace an old electric gravity water heater 1.5 years ago. Based on power meter data it uses 30% of the energy of the old system on average. This is probably understated as hot water consumption has gone up as the new system and new pipes increased pressure and flow. I say on average as there is seasonality to the energy consumption. I live in a temperate climate, no snow.

We run it at night to take advantage of cheaper separately metered electricity rates ('controlled load'), it could be run even more efficiently during the day, but at higher cost. This and replacing the old gas ducted heating with reverse cycle air conditioning has allowed us to stop using gas, saving the fixed $~30/month service charge. Eventually the additional of solar will further increase our use of renewables.