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Polishing of anaerobic secondary effluent by Chlorella vulgaris under low light intensity

Cheng, Tuoyuan, Wei, Chun-Hai, Leiknes, TorOve
Bioresource technology 2017 v.241 pp. 360-368
Chlorella vulgaris, ammonium nitrogen, biomass, chemical oxygen demand, hexane, membrane bioreactors, microalgae, nitrogen, nutrients, oils, phosphates, phosphorus, ultrafiltration
To investigate anaerobic secondary effluent polishing by microalgae (Chlorella vulgaris) under low light intensity (14μmol/m2/s), bubbling column reactors were operated in batches of 8 d with initial ammonium nitrogen 10–50mg/L, initial phosphate phosphorus 2–10mg/L and microalgal seed 40mg/L. Maximum microalgal biomass and minimum generation time were 370.9mg/L and 2.5d, respectively. Nitrogen removal (maximum 99.6%) was mainly attributed to microalgal growth rate, while phosphorus removal (maximum 49.8%) was related to microalgal growth rate, cell phosphorus content (maximum 1.5%) and initial nutrients ratio. Dissolved microalgal organics release in terms of chemical oxygen demand (maximum 63.2mg/L) and hexane extractable material (i.e., oil and grease, maximum 8.5mg/L) was firstly reported and mainly affected by nitrogen deficiency and deteriorated effluent quality. Ultrafiltration critical flux (16.6–39.5L/m2/h) showed negative linear correlation to microalgal biomass. Anaerobic membrane bioreactor effluent polishing showed similar results with slight inhibition to synthetic effluent.