Dear Kris,

Separated storm-water sewers with decentralized infiltration are usually discarded because of seemingly much higher costs. However this rarely takes into consideration the larger impacts on the overall water cycle and dropping ground-water tables (and salt-water intrusion in coastal cities).
I think most of the experts agree on this though, it is more of an issue that budget allocation usually goes for the "cheaper" option.

I think this is especially true in a place like Nepal, where 85% of the annual precip falls in a 3.5 month period. If we can locally infiltrate storm water, the waste water treatment solutions (centralized or de-centralized) could be designed so much more efficiently.

Marijn

Marijn Zandee wrote: • Grey water separation and decentralized treatment (same for rainwater), is totally feasible. It should be promoted much more “aggressively”.

Separated storm-water sewers with decentralized infiltration are usually discarded because of seemingly much higher costs. However this rarely takes into consideration the larger impacts on the overall water cycle and dropping ground-water tables (and salt-water intrusion in coastal cities).
I think most of the experts agree on this though, it is more of an issue that budget allocation usually goes for the "cheaper" option.

Marijn Zandee wrote: • The “BAMBi” filter that EAWAG uses in the “blue toilet”, may also find application in greywater treatment systems in many places with space limitations.

This is kind of funny if you know the history behind these gravity driven membrane filters. The system I worked with started out as a creative re-use of UF membranes from waste-water MBRs, was then converted for emergency/low cost drinking water treatment, then EAWAG thought their GDM drinking water treatment system could also be used for treating the wash-water in their toilet... and now it is back at waste-water

Dear all,

I recently had the opportunity to participate in the “IWA specialist conference Global challenges: Sustainable wastewater treatment and resource recovery” here in Kathmandu. Which was quite interesting, and I would like to share some messages and impressions.

The thing that surprised me most during the conference is how many research institutes, companies and utilities are working on nutrient and energy recovery in the developed world these days. The subject really seems to have “exploded” in recent years. Considering some of the recent discussions regarding what is and is not “Ecosan” on the forum. Maybe we also have to expand the forum somehow and come up with a new category where people can post information regarding resource recovery from centralized wastewater treatment plants?

Below I will list some other points that I found interesting. Many may not be new, but still good to remember:

• In many developing / middle income countries (and in developed ones too), the way invitations to tender for wastewater treatment systems are written more or less dictate a “classic” WWTP.

• In the developed world, where WWPTs are already common, it seems that many to ideas achieve energy neutrality and resource recovery are based on adding other (organic) wastes to the processes in the plants. While this may make sense for ‘Industrial size” WWTPs it still seems to me that separation is a better way to go in the developing world.

• Grey water separation and decentralized treatment (same for rainwater), is totally feasible. It should be promoted much more “aggressively”.

• The “BAMBi” filter that EAWAG uses in the “blue toilet”, may also find application in greywater treatment systems in many places with space limitations.

• Waste water is almost all water, future developments in places with water scarcity (Australia, parts of the USA), are likely to be driven by water prices (and the desire for drinking water quality effluent), rather than other recovery options.

• One way to prevent failures of lager waste water treatment systems in developing nations is to use a model where the company who installs the system also has to operate it for 15 years or so.

Regards

Marijn