Abstract |
Spent powdered activated carbon from secondary effluent treatment has been successfully dewatered by continuous membrane ultrafiltration. 5 and 10% carbon solids concentration slurries, using a laboratory size thin channel (0.1 sq ft membrane area), have been dewatered by continuous ultrafiltration to solids levels of 25 to 30%. Dewatering rates ranged between 50 and 100 gal/sq ft day at transmembrane pressures of from 10 to 50 psi during runs as long as 9 days, and product water was invariably free of any suspended carbon solids. The cost of membrane ultrafiltration depends upon the membrane life, and at membrane flux rates of 50 gal/sq ft day the cost of dewatering carbon from 10 to 20% solids is $0.0015 per pound of carbon with a membrane life of six months, and $0.0035 per pound with a membrane life of only one month. At the present no conclusive data on membrane life is available, but estimates of between 1 and 6 months are quite common and seen to be reasonable. (WRSIC abstract) |