BTW Urine Diverting Riser
The BTW (behind the wall) toilet riser diverts >99% of urine away from solid waste (poop, toilet paper, and trash). Urine is plumbed to onsite treatment by conventional septic field or containerized filtration by sand and fixed media. Solid waste is conveyed up a foot-powered belt and drops into a behind-the-wall earthen bottom vault (the Decompose type) or to a container or bag (the Waste Away). A heavy-duty, white, fiberglass or plastic riser is included with the BTW urine diversion conveyor.
>99% urine diversion; men can stand and pee; very robust; commercial strength
Could be damaged by an explosive; may not be ideal for urban parks with vandals
From extreme back-country environments to front-country climbing areas
Importance of Urine Diversion
Urine diversion or source separation of urine is the critical component in the development of a low cost, low odor, low waste volume system. Providing drainage of blackwater from the bottom of a pile of soaked feces is not urine diversion. When fecal waste has been saturated with urine, the urea in urine changes to ammonia, and prevents all bacterial and invertebrate life from decomposing the pile, and makes the waste soggy and smelly (avoid this).
The BTW seat diverts >99% of urine directly to an on-site septic field for treatment and disposal. This leaves the solid waste primarily comprised of dry low-density toilet paper and some feces. This high cellulose feedstock can be consumed (actually ingested) by bugs (worms, nematodes, slugs, and other insects). Passing through the gut of the bug, the majority of pathogens are destroyed and the waste is highly stabilized, odor eliminated, and volume diminished. TTS' Director, Dr. Hill, did his PhD work on this topic, references here.
What's in Urine and How is it Treated and Dispersed Onsite?
Urine is largely sterile when leaving the body, has high levels of plant nutrients, almost no heavy metals, flows by gravity, and self sanitizes when stored for 2-3 weeks. Fecal matter contains pathogens, metals, and has few plant nutrients, and is sticky. Of great importance to the backcountry manager, 70-90% of human waste volume and mass is urine. BTW systems divert urine away from fecal matter at the source (no mixing) so that pure urine can be stored or treated and disposed of immediately by a conventional gravity-fed septic field/leach field. This eliminates the vast majority of waste with little effort on the part of park management. Only 100-200 ml of urine are generated each use, so even at a high use toilet, used 100 times a day, less than 5 gallons of urine will be produced. This is 200x less than the standard residential septic field receives and processes. As such, the urine septic field for remote toilets can be quite short and still be conservatively over-sized. Depending on the soil type, the length can be as short as 10' long and 1' wide.