Can I disaggregate a sector with a different activity level within another demand site?, e.g. a sugar factory(production units) within an urban demand site(persons) or must I create a separate demand site for it?

Yes, you can disaggregate a demand site to as much detail as you want, with each having its own activity level and water use rates. Look in the WEAP User Guide (http://www.weap21.org/downloads/WEAP_User_Guide.pdf), Section 4.4.2 Demand Tree, page 39 for more information and an example.

Jack

Yes!! You can disaggreagate demands... But let me discribe something to you...
As I got, you want to compute some supply-Demand Activity. Thus you want to know how much water you can allocate to a certain demand (or demand site)... and as I know potabel water has always first priority. Don't you think that it is better to divide this demands?
By the way.... from one demand site, you can make disaggregate your data.

Good point. You can disaggregate demands within one demand site, for
example, for potable water and for industrial use. However, if the
demands will have different priorities, preferred supply sources,
pollution generation, return flow fractions and monthly variations,
perhaps it is better to separate into two (or more) demand sites.

Jack