A high rate ponding unit operation linking treatment of tannery effluent and Arthrospira (Spirulina) biomass production. 1: Process development

Abstract

Effluent from the production of wet blue leather has been shown to support the substantial growth of Arthrospira biomass in tannery waste stabilization ponds, which is of interest in its use both in animal feeds and biofuels production. Here we report process development investigations which were undertaken in photobioreactor and outdoor high rate pond pilot studies. Biomass productivities of 16 t ha−1 yr−1 (dry mass) were measured which compares broadly with yields reported for Arthrospira cultivated in other complex media. The specific growth rate μ = 0.05 d−1 was somewhat lower than reports for the mixotrophic cultivation of Arthrospira in defined media studies. This system operates under ammonia control and may be relieved by recirculation of alkaline waters which accumulate in these waste stabilization ponds. A substantial difference in total nitrogen and phosphorus removal between the experimental and theoretical yields due to biological activity suggests stripping may account for the largest fraction of ammonia removal, and precipitation for phosphate removal, in this operation. Heavy metal contamination may be a problem with biomass production in industrial effluents and pretreatment of the tannery effluent in a primary facultative pond was shown to substantially reduce the heavy metal load. Process kinetic values were derived and have been used for the design and construction of a full-scale Arthrospira production operation using tannery effluent growth media, which is reported in a follow-up study.