Table 142

Chemical Constituents of Activated Sludge Solids and Liquid Phases

Sample

Solids Liquid

Total Solids gl-1

Volatile Solids (gl-1)

Protein (mgl-1)

Humics (mgl-1)

Carbohydrate (mgl-1)

Uronic Acids (mgl-1)

BDb pH

NDa 7.2

a Not determined. b Below detection.

FIGURE 14.2 PO4ase activity in activated sludge fractions. Samples assayed at 500 ¡M MUF-PO4: (O) "as collected" activated sludge, 15.2 xmoll-1h-1; (v) resuspended floc, 18.4 xmoll-1h-1; (■) activated sludge supernatant, 0.1 xmoll-1h-1; and samples assayed at 100 ¡M MUF-PO4: (#)"as collected" activated sludge, 8.7 ¡moll-1 h-1; (▼) resuspended floc, 7.9 ¡moll-1 h-1.

FIGURE 14.2 PO4ase activity in activated sludge fractions. Samples assayed at 500 ¡M MUF-PO4: (O) "as collected" activated sludge, 15.2 xmoll-1h-1; (v) resuspended floc, 18.4 xmoll-1h-1; (■) activated sludge supernatant, 0.1 xmoll-1h-1; and samples assayed at 100 ¡M MUF-PO4: (#)"as collected" activated sludge, 8.7 ¡moll-1 h-1; (▼) resuspended floc, 7.9 ¡moll-1 h-1.

MUFP concentrations yielded a Vmax of 2 x 104 ¡moll-1 h-1 and Km of 133 ¡M with respect to MUFP (Figure 14.3). Conversion of MUFP to MUF was not the result of abiotic reactions since autoclave sterilization of the activated sludge samples before addition of the MUFP yielded no fluorescent product.

Additional evidence for the enzymatic release of Pi from detrital organic-P in activated sludge was obtained by following the concentration of Pi in samples of activated sludge under different conditions. Autoclave-sterilized activated sludge showed no change in Pi concentration over a 24-h period (Figure 14.4). Treatment of activated sludge with benzene to arrest growth of microorganisms present, but to allow PO4ases present to remain active, resulted in an increase in Pi from 13.6 to 18.8 xg ml-1 over a 24-h period (Figure 14.4), suggesting the production of new Pi from polyphosphate (poly-P) or organic-P sources present in the activated sludge. That benzene arrested the growth of the microorganisms in the activated sludge was demonstrated by recovering the same number of colony-forming units (cfus) at the end of the

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