23 JULY 2003
system to the filter press. To ensure proper chemical conditioning dosages, the lime
slurry and ferric chloride feed systems are also equipped with variable-speed pumps
that are controlled to match the proportional sludge flow rate into the conditioning tank.
This system offers the advantages of maintaining a nearly constant retention time, but
requires pumps with wider ranges of capabilities and variable-speed drives, and
requires complex controls.
e. The second method uses sludge transfer and conditioning feed pumps.
This system typically requires the use of intermittent but constant sludge transfer to the
conditioning tank, with constant and manually adjustable control of chemical
conditioning feed systems. Because this process involves intermittent sludge transfer, it
also involves varying the level in the conditioning tank. Because the level in the
retention tank varies, an increase in the capacity of the conditioning tank is typically
required; however, less complex controls are required. This system may be more useful
for smaller filter presses or those requiring less automatic or complex control.
f. In addition to the sludge transfer pumps, the volume of the conditioning
tank, chemical conditioning systems, and associated feed pumps must be sized to meet
the sludge feed requirements to the press. To meet changing requirements of uncondi-
tioned sludge, the chemical conditioning systems must also be flexible enough to ac-
commodate a range of chemical dosages.
2-188.8.131.52 Polymer Conditioning. Organic chemicals used for sludge conditioning are
primarily synthetic organic polymers. Although these polymers were originally used
primarily for wastewater and easily dewatered sludge, they are now being used as a
conditioning aid or as the primary conditioning chemical for all types of sludge. Poly-
mers in solution typically have chemical reactions that are similar to those of inorganic
chemicals, such as neutralizing surface changes and bridging of particles.
a. Polymers consist of three different charge types (anionic, cationic, and non-
ionic) and are commercially available in several forms including dry, liquid, emulsion,
gel, and Mannich polymers. The most commonly used polymers for filter press
applications are dry and liquid-type. The other types (i.e., emulsion, gel, and Mannich)
are not as commonly used, but may be appropriate for some applications. Additional
details for these types of polymer are presented in the publication Design of Municipal
Wastewater Treatment Plants-Manual of Practice No. 8 (WEF 1992).