Biosolids Alternative Analyis

City of Santa Barbara, 
California

Biosolids Alternative Analyis

Service Type: 
Project Highlights: 
  • Development of a plan to produce Class A biosolids.
  • Solids processing systems design.
  • Obtaining consensus decisions and support for proposed wastewater facility modifications.
  • The consultant was responsible for cost estimates and construction schedule.
Santa Barbara digester
Carollo determined that chemical addition would be a costeffective technology to achieve Class A biosolids due mainly to the reuse of available building space.

The City hired Carollo to evaluate alternative methods toward the goal of developing long-term solutions for handling of biosolids. This Biosolids Alternative Evaluation included:

  • Evaluation of alternative methods of beneficial reuse to develop longterm solutions for biosolids handling and to produce Class A biosolids that could be distributed or marketed for pubic reuse within the City limits. This effort focused on alternatives that can be implemented within the present confines of the El Estero Wastewater Treatment Plant and alternatives for further treatment that will produce a high grade Class A product.
  • Evaluation of potential upgrades and enhancements to existing plant facilities to determine the cost-effectiveness of assisting the production of high quality Class A biosolids. A key recommendation of replacing the existing belt dewatering presses with centrifuges was not costeffective.

This was a collaborative effort between the City staff and Carollo. Carollo prepared technical memoranda which presented and evaluated alternatives based on capital, operations, and maintenance costs, site limitations, potential nuisances, regulatory constraints, and the other more subjective considerations which enter into the decision-making process. Since the alternatives available for reuse/disposal of the treatment biosolids effect the requirements for digestion, dewatering, and drying, Carollo and the City communicated regularly. The alternatives considered included three-phase digestion, in-vessel composting, heat drying, and chemical addition.

An additional part of this project was a digester analysis. The analysis included the alternatives from ongoing WERF anaerobic digestion research, and research and implementation being conducted by Carollo on two-phased digestion. The review included mixing improvements and evaluating changes to the process type (two-stage versus two-phase) and operating temperature (thermophilic versus mesophilic) at the wastewater treatment plant.

The project also included preparation of a strategic plan for high quality Class A biosolids. Key recommendations defined that chemical addition is the most costeffective alternative based primarily on the existing site’s spatial restrictions and alternatives cost-effectiveness of utilizing existing structures.

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