It will also cause huge weed overgrowth, temporarily soaking up some CO2, yes.  But it will be rereleased (in a 21x worse GHG form) as that weed overgrowth kills the lakes and the weeds and fish die and turn into methane too.

I recently found out that human urine contains all the fertilizer needed to grow enough crops to feed that person's needs in the food chain.  Then on the Green network they showed the simple 2 part process that separates the fertilizer in the urine so it can replace chemical fertilizer.

And of course the compounds dumped in the waterways from urine, like hormones and antibiotics are killing and mutating wildlife,  

It strikes me that recycling the fertilizer from urine and replacing ever more expensive shipped and mined fertilizer would more than pay for breaking down the contaminants in the waste stream and keeping our aquifers safe and actually recycling waste water itself.