Managing nutrients at the centralized wastewater treatment scale has been a major focus of the environmental engineering field for decades. Recently, focus has shifted to sewershed management of nutrients, i.e. the management of nutrients along the collection system. Building-scale treatment of urine provides the opportunity to recover valuable nutrients at the point of entry into the collection system. This project specifically seeks to reduce the precipitation of struvite, a crystalline solid that can be used as a slow-release fertilizer, by treating urine closely after it enters waterless bathroom fixtures. Treatment can also reduce maintenance problems, such as clogging and malodor, which can ultimately dictate the current and future installation of water-saving bathroom fixtures. The treatment method that has been tested is as follows. A person uses a waterless fixture as it is conventionally used. Once the person walks away from the fixture, a small dose of acid is introduced into the waterless fixture. This would occur after each urination event. The user of the waterless fixture would have no interaction with the technology.
This treatment method is unique because of its ability to positively impact two widely different wastewater treatment scenarios. As described above, installing this technology in conventionalbathrooms outfitted with waterless fixtures can reduce clogging and malodor, which in turn increases water conservation and public approval of the waterless fixtures. Additionally, this technology can be coupled with urine source separation operations. Urine can be diverted and collected within the building, stored for disinfection, and then treated to recover value nutrients. Waterless fixtures are ideal in these operations because urine is collected without the dilution of flushing water. However, the precipitation of nutrients inside the fixtures reduces the amount of nutrients that can be beneficially recovered in the storage units. This small addition to the way waterless fixtures are installed today has the possibility of positively impacting wastewater systems of today and the future.