Genetic improvement of Magnetospirillum gryphiswaldense for enhanced biological removal of phosphate.

OBJECTIVES: To improve its phosphate accumulating abilities for phosphate recycling from wastewater, a magnetotactic bacterium, Magnetospirillum gryphiswaldense, was genetically modified to over-express polyphosphate kinase. RESULTS: Polyphosphate kinase was over-expressed in the bacterium. The recombinant strain accumulated ninefold more polyphosphate from synthetic wastewater compared to original wild type. The magnetic property of the recombinant M. gryphiswaldense strain was retained. CONCLUSIONS: The recombinant M. gryphiswaldense can be used for phosphate removal and recovery in bioremediation.

Removal of biofilms by intermittent low-intensity ultrasonication triggered bursting of microbubbles.

In this study, a chemical-free cleaning method for biofilms removal is presented, which is based on intermittent low-intensity ultrasonication (US) triggered bursting of microbubbles (MB) in such a sequence that MB were continuously introduced into the reaction vessel for 15 min, while US was activated for 2 s after every 2 min of microbubbling. It was found that the fixed biomass, and the extracellular proteins and polysaccharides of 24-h old biofilms grown on a nylon membrane surface were reduced, respectively, by 75, 79 and 72% after treatment by the US + MB method. Fourier transform infrared (FTIR) analysis further revealed that the chemical composition of the biofilms was not altered by the US + MB treatment, suggesting that biofilms were removed through physical forces due to the generation of a shock wave and a high-speed water jet through US-triggered bursting of the MB. The proposed method can be considered a chemical-free technology for biofilm removal.

A model for decentralised grey wastewater treatment system in Singapore public housing.

Global concerns over the sustainable use of natural resources provided the impetus for research into water reclamation from wastewater within the Singapore context. The objective of the research is to study and develop a water infrastructure system as an integral element of architecture and the urbanscape, thereby reducing the need for the large area requirements associated with centralised treatment plants. The decentralised plants were considered so as to break up the large contiguous plot of land otherwise needed, into smaller integrated fragments, which can be incorporated within the housing scheme. This liberated more usable space on the ground plane of the urban housing master plan, enabling water-edge and waterscape relationships within both the private and public domains of varying scale.