Under the aegis of the DST’s All India Coordinated project on Algae, NBRI had developed a soft technology for Spirulina production in sewage. Without being a health hazard, total use of sewage is envisaged for production of algal proteins (as animal feed), fish-culture and for irrigation water in an integrated pilot plant system. After extensive bench and field experiments, it has been possible to adapt Spirulina to raw and settled sewage, using sodium bicarbonate as a carbon source as also to maintain a high pH, required for satisfactory growth of algae. A system, therefore, of raw sewage, fortified with sodium bicarbanate (9g/l) and sodium nitrate (1.0g/l), has been developed which works very well and the alga grows profusely, without contamination. The major steps in the cultivation of S. platensis are preparation of inoculum, mass outdoor cultivation in high-rate oxidation pond...