Acid regression stage of sludge digestion at a temperature 21°C extends over a period of______________?

A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares

A. Size of the sewer
B. Shape of the sewer
C. Roughness of sewer surface
D. All the above

A. 2 metres/sec
B. 1 metre/sec
C. 0.5 metre/sec
D. 0.25 metre/sec

A. Vs = 418 (Gs – Gw) d [(3T + 70)/100]
B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100]
C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100]
D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]

A. Large suspended organic solids
B. Oil and grease
C. Sand and girt
D. Floating materials