Studies on the Technical Challenges of Urine Source-Separation Technology and its Microbial Ecology

Waterless and low-flow urinals offer a way to minimize potable water consumption and collect urine for downstream nutrient recovery; however, its practicality and social acceptability is hindered by technical problems such as biomineral pipe fouling. Understanding the biology of the urine drainage systems and factors that influence key reactions will provide insight when developing treatment methods to prevent pipe fouling in urine drainage systems. To understand the biomineral fouling, a four-part study was developed which consists of (1) a literature review, (2) biogeographic microbial ecology study, (3) a multiple regression study to determine the influencers of biomineral urease activity, and (4) an exploratory study on the use of an agricultural urease inhibitor, n-butyl thiophosphoric triamide, to minimize biomineral formation in urine source-separation systems

Modulation of struvite composition in full-scale nutrient recovery system using source-separated urine

Using urine collected from a public restroom at a highway rest stop in Northern California, a full-scale nutrient recovery system involving a two-part system consisting of urine distillation followed by the precipitation of struvite crystals was characterized. The study examined the effects of different operational parameters of the coupled ammonium distillation and struvite process (CADSP) on the composition of struvite crystals and the overall nutrient recovery rates. System inputs that were investigated included the feed:steam (F:S), alkalinity source, and urinary pH. Overall, the findings demonstrate that the composition of the struvite produced can be varied by adjusting the preceding distillation unit process. Low F:S distillation operations result in high ammonium distillation rates which coincided with increased formation of magnesium potassium phosphate (MPP) while higher F:S operations led to conditions favorable to magnesium ammonium phosphate (MAP) precipitation. Therefore, low energy distillation operations (high F:S) are more conducive to MAP formation and high phosphorus recovery rates while high energy operations (Iow F:S) are more conducive to MPP formation. Sodium-based alkalinity sources should also be avoided in instances of low ammonium concentrations in the struvite precipitation tank to minimize the co-precipitation of magnesium sodium phosphate (MSP) with MPP. HIGHLIGHTS A full-scale NPK recovery from urine was operated at a highway rest stop.; Process used coupled steam distillation and struvite precipitation.; Distillation feed to steam ratio (F:S) was a key variable for overall performance.; Low F:S resulted in decreased phosphorus recovery by precipitation.; High F:S favored magnesium ammonium phosphate crystallization.

A biogeographic 16S rRNA survey of bacterial communities of ureolytic biomineralization from California public restrooms

In this study, we examined the total bacterial community associated with ureolytic biomineralization from urine drainage systems. Biomineral samples were obtained from 11 California Department of Transportation public restrooms fitted with waterless, low-flow, or conventional urinals in 2019. Following high throughput 16S rRNA Illumina sequences processed using the DADA2 pipeline, the microbial diversity assessment of 169 biomineral and urine samples resulted in 3,869 reference sequences aggregated as 598 operational taxonomic units (OTUs). Using PERMANOVA testing, we found strong, significant differences between biomineral samples grouped by intrasystem sampling location and urinal type. Biomineral microbial community profiles and alpha diversities differed significantly when controlling for sampling season. Observational statistics revealed that biomineral samples obtained from waterless urinals contained the largest ureC/16S gene copy ratios and were the least diverse urinal type in terms of Shannon indices. Waterless urinal biomineral samples were largely dominated by the Bacilli class (86.1%) compared to low-flow (41.3%) and conventional samples (20.5%), and had the fewest genera that account for less than 2.5% relative abundance per OTU. Our findings are useful for future microbial ecology studies of urine source-separation technologies, as we have established a comparative basis using a large sample size and study area