Comparing three methods for photosynthetic bacteria separation and recycling during wastewater treatment

Abstract

Photosynthetic bacteria (PSB) wastewater treatment technology can simultaneously treat wastewater and produce valuable materials. However, PSB are typically difficult to collect from wastewater, which limits their utilization in wastewater treatment and resource recovery. In this study, three different methods (e.g. immobilization, coagulation and membrane separation) were investigated and compared for PSB collection to recover bioresources. A strain of PSB, Z08 (Rhodobacter sphaeroides) was used. Results showed that PSB hardly attached to the seven support materials tested during immobilization. Aluminium polychloride was shown to be effective at PSB separation via coagulation at a dosage of 5,000 mg/L; however, coagulants might cause the second pollution. Also, the membrane was effective at Z08 collection. Ninety-nine per cent of PSB was collected from water; this PSB liquid was then concentrated by a factor of 12.4, and the water production ratio reached 93.0%. The optimal Z08 dosage was 1,682.1 mg/L, which generated 165,396.0 mg/L of biomass within a 50 h water cycle. Compared with activated sludge, the water cycle that combines the PSB and the membrane can function up to 60 min with an initial PSB concentration of 10,000 mg/L, which will mitigate membrane fouling and achieve bioresource recovery.

Keywords:

• Photosynthetic bacteria
• Bioresource recovery
• Membrane separation
• Coagulation
• Immobilization

Acknowledgements

The authors would like to thank the National Natural Science Foundation of China (51308535, 51278489) and MARC (MARC2012D011) for their financial support.