MASS AND VIABILITY ESTIMATIONS OF NOCARDIA IN ACTIVATED-SLUDGE AND ANAEROBIC DIGESTERS USING CONVENTIONAL STAINS AND IMMUNOFLUORESCENT METHODS

An immunofluorescent method was developed to estimate the quantity and viability of Nocardia filaments in activated sludge and anaerobically digested sludge on both a mass and volume basis. The Gram stain count ing technique of Vega-Rodriguez (1983) and Pitt (1988) was modified to estimate the mass of Nocardia in activated sludge and compared to the immunofluorescent method. Both methods were calibrated on a pure cult ure of chemostat grown Nocardia amarae. Using the immunofluorescence t echnique, Nocardia were estimated to comprise an average of 18% by wei ght of the VSS in a foaming activated sludge plant. Nocardia were foun d to be, on average, 79% viable as judged by INT reduction staining. N ocardia were found to comprise 13% of the VSS in a foaming anaerobic d igester sludge and had an average viability of 63%. These organisms we re estimated to be 30 to 50% viable in a mixed anaerobic digester with a hydraulic detention time of 14 days.