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Date: September 17, 1999 - page 5 / 9

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On-Site Holding/Contract Beneficial Reuse

This technology makes use of maintaining the dewatered

biosolids on-site (on an asphalt standards. The biosolids could

pad) for 90 days. This would then be removed, by a contract

allow the biosolids to meet Class hauler, for beneficial reuse outside

B of

Prescott Valley. This process disposal to local landfill.

was

employed

prior

to

the

current

practice

of

dewatering

followed

by

Advantages

  • Low capital costs

  • Low energy costs

  • Low risk, with respect to biosolids reuse

  • Low operations and maintenance requirements

  • Low noise potential

Disadvantages

  • High contract hauling and reuse costs

  • Moderate odor potential

  • No beneficial reuse within Prescott Valley

Agitated Air Drying and Curing

This technology is a batch process in which unstabilized dewatered

biosolids are spread on an impermeable paved asphalt pad and are subject to mechanical agitation.

Small

windrows

are

created

approximately

12

to

16

inches

in

height.

When

unstabilized

solids

concentrations

are

low

(15%-20%), an amount of drier (65%) stabilized material is mixed in (recycled)

to bring the initial solids concentration up to approximately 40%. are then dried in the windrows as the machine is moved through

The wet surfaces of the biosolids the material. The curing process

follows this. The porosity

The curing process occurs when of the material allows aeration

the material is stored for an adequate period of time. by convection, with heat build-up from the aerobic

biological breakdown of the residual up plus proper storage time allows biosolids requirements.

volatile matter in the solids and from for pathogenic organism destruction,

insulation. The heat build- required to meet Class A

Advantages

  • Low/moderate capital costs

  • Low operations and maintenance requirements

  • Low energy costs

  • Low noise potential

  • Beneficial reuse options within Prescott Valley

Disadvantages

  • Moderate/high land requirements

  • Moderate odor potential

Autothermophilic Aerobic Digestion

closed

and

insulated

tanks.

The

This technology tanks are aerated

is a batch process that makes use of a series of and mixed, similar to conventional aerobic

digestion. When waste sludge is volatile organic compounds. This insulated the bulk liquid heats up.

added to the tank the biological organisms proceed to oxidize the biological reactions produces heat. Since the tankage is closed and The temperatures reaches the thermophilic range of 120*F-135*F.

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