Nitrification and microalgae cultivation for two-stage biological nutrient valorization from source separated urine

Abstract

Urine contains the majority of nutrients in urban wastewaters and is an ideal nutrient recovery target. In this study, stabilization of real undiluted urine through nitrification and subsequent microalgae cultivation were explored as strategy for biological nutrient recovery. A nitrifying inoculum screening revealed a commercial aquaculture inoculum to have the highest halotolerance. This inoculum was compared with municipal activated sludge for the start-up of two nitrification membrane bioreactors. Complete nitrification of undiluted urine was achieved in both systems at a conductivity of 75mScm(-1) and loading rate above 450mgNL(-1)d(-1). The halotolerant inoculum shortened the start-up time with 54%. Nitrite oxidizers showed faster salt adaptation and Nitrobacter spp. became the dominant nitrite oxidizers. Nitrified urine as growth medium for Arthrospira platensis demonstrated superior growth compared to untreated urine and resulted in a high protein content of 62%. This two-stage strategy is therefore a promising approach for biological nutrient recovery.

Media Optimization, Strain Compatibility, and Low-Shear Modeled Microgravity Exposure of Synthetic Microbial Communities for Urine Nitrification in Regenerative Life-Support Systems

“…The application of nitrified urine was not evaluated. In a scenario in which urine nitrification will be required at high EC, for the cultivation of halophytes, salt adaptation of the microbial inoculum is a promising option (Coppens et al, 2016). Alternatively, although still requiring optimization, selective ion removal to ensure the optimal salinity can be obtained through electrodialysis, salt precipitation, or electrochemical technology (De Paepe et al, 2018).…”

“…To elucidate the impact of salinity and the minimum level of urea to induce ureolysis, the ureolytic activity of the strains was evaluated in an artificial urine salt matrix with different levels of salinity, corresponding to electrical conductivity (EC) levels reported for nitrification systems treating 10%, 20%, and 60% real urine (5, 10, and 30 mS cm -1 , respectively) (Coppens et al, 2016;De Paepe et al, 2018) and a low urea concentration (10, 25, or 50 mg-N L -1 , for each salinity tested). Since urine contains also multiple forms of organic nitrogen (Bouatra et al, 2013), the ureolysis was evaluated in the presence of different concentrations of a mixture of amino acids (130, 65, and 33 mg L -1 ) (Kim et al, 2013).…”

Antioxidant, Immunomodulating, and Microbial‐Modulating Activities of the Sustainable and Ecofriendly Spirulina

“…In the context of the bioremediation, Spirulina is considered a candidate for the removal of toxicants, such as heavy metals [ 1 – 5 ] and phenol [ 6 ]. Besides, within microalgae and cyanobacteria Spirulina showed maximum biomass productivity with the highest CO 2 fixation rate [ 7 ] and it has been suggested for the nitrification from urine in urban wastewaters [ 8 ]. The environmentally friendly Spirulina does not need fertile land, has a rapid growth, and takes less energy input and less water per kilogram than soya and corn proteins [ 9 ].…”

Control tools to selectively produce purple bacteria for microbial protein in raceway reactors

“…6 This was probably due to the higher growth rates of PNSB of 0.6-3.7 d -1 compared to the ones of microalgae of 0.60-1.38 d -1 . 13,33,34 To a lesser extent, non-PNSB chemotrophs also contributed to biomass production in the raceway reactor, thereby increasing the overall biomass productivity.…”