Proceedings

Rectangular primary settlement tanks are often used on large wastewater treatment works as they offer a smaller footprint than the circular alternative. Scraping of the settled sludge and surface scum to remove it from the system is important, and this has normally been achieved either by travelling bridges or chain and flight systems. Zickert reciprocating scrapers offer another important and effective alternative.

The Zickert Scraper is a reciprocating scraper using a framework welded lattice of shaped profiled blades to move the sludge to the hopper end of the tank and a ratchet suspended blade for scum removal. The low head-space requirements of this system facilitate installation of low-profile covers, and therefore less expensive odour control measures. A case study of large primary settlement tank installations is presented along with comparative results against the conventional travelling bridge system.

KEY WORDS: Primary treatment, Solids Removal, Sludge removal, Odour control, Scraper, BOD removal, TSS removal.