The right question to ask is what do end-users get in terms of water quality.
I had a fairly in-depth discussion on this with one of the members of my dissertation committee previously and this is why we concluded:
Centralized water treatment isn't cost-effective, and decentralized treatment is the way to go. Why treat massive quantities of water to levels which is extremely clean, only to let it flow down near-century old leaky, degraded old pipe infrastructure which greatly diminishes its quality when it reaches your tap. 10-50% of the water pumped through the aged-mains leak into the ground and all that treatment you subject it to essentially goes to waste.
A better water treatment strategy would be to pump raw reservoir water through the aged mains and to smaller neighbourhood treatment plants where water is only treated to 3 varying standards of quality near point of use (POU) - high-grade industrial use (UF-RO-DI, Newater quality), drinking (UF- activated carbon filter) and grey water (effectively just Sand or MF-filtered - mainly for flushing, watering plants, purposes where you just need water of a okay quality etc).
Effectively you only treat enough water to sufficient standards for its final use. Certainly the amount of high quality wastage would be less.
Unfortunately, such an infrastructure would require quite an extensive re-work of our existing water infrastructure, but its mostly near the POU end. Given that we're in economic doldrums now, it'll be a nice and much needed stimulus package, if the government wants to do this. This infrastructure is also alot more labour intensive in terms of operational maintenance, which probably helps to put more people into employment. Certainly something which the EDB would like.
A similar system re-work should work for wastewater treatment infrastructure as well. Decentralize segments of the system to focus on priority points of discharge (POD), particularly those heavy/manufacturing industry and pharma production discharge points. These industries typicially discharge wastewater with high heavy metal and non-biodegradable hydrocarbon/Endocrine Disrupting Compounds(EDC) content, and its much easier to treat these sources of wastewater at point source with the appropriate wastewater treatment techniques when the pollutants are highly concentrated, rather centralizing these flows and thus greatly diluting the pollutant concentration, which makes it much harder to comprehensively treat (although dilution does hide the problem very well).
After the critical POD streams have been treated to effluent quality satisfying that of typical municipal discharge, then would it be appropriate to mix the streams for a more centralized treatment approach.
Even then, you certainly don't need to do MBR-UF-RO Newater style treatment to get the water to reclaimable quality standards. A simple UF-MBR-carbon filter configuration would get the water quality to standards good enough for reservoir storage for total recycle.
By the way, EDCs (which includes synthetic hormone equivalents, synthetic biological compound equivalents - like your sugar substitutes.) are actually not that hard to remove. You just need to adsorb them onto a highly adsorptive media, and replace the media periodically when it gets saturated.
Just my 2 cents.
Cheers,
Trout
