1. How important is it to perform bench, pilot, and/or demonstration-scale evaluations?
While bench-scale evaluations may have value for establishing treatability, pilot- and demonstration-scale testing is a critical precursor to full-scale implementation. These tests will support optimization of design and operational parameters.
2. What are the costs associated with performing these evaluations?
Evaluation costs are generally a function of scale, duration, equipment procurement, and analytical requirements. Short duration bench-scale evaluations can cost $30,000, while longer-term, large-scale evaluations where pilot equipment is procured can be over $1.5 million.
3. Water are target performance criteria for these evaluations?
Typical performance criteria include maintaining filtered turbidity below 0.1 NTU, filter run time greater than 24 hours, unit filter run volume greater than 10,000 gal/ft2, and target contaminant removal (e.g., greater than 20 percent TOC removal). In all cases, these performance criteria should be tailored to the specific needs of the facility.
4. Are there performance data available in the knowledge base?
Full-scale operational data are summarized in the knowledge base report and in select case studies.
5. How long should I run an evaluation?
It is recommended that evaluations be run long enough to achieve biological operation mode followed by a period that includes seasonal fluctuations in water quality. Pilot- or full-scale evaluation durations can be as short as six months, but are recommended to be at least one year.
6. How do the evaluation results translate to full scale?
Some utilities have had difficulty in achieving full-scale performance predicted by bench- or pilot-scale tests. Therefore, it is valuable to run a demonstration-scale evaluation on a single full-scale filter once process optimization has been achieved at pilot-scale.
7. What media and media configuration should I use for the evaluation?
Most utilities have dual-media filters comprised of anthracite and sand or GAC and sand. There are various types of GAC available for evaluation. Most utilities use bituminous GAC.
8. Can I expedite the acclimation of the biofilters?
Acclimation of biofilters has been reported to range from two weeks to six months. At this time, there are no reliable methods for expediting biofilter acclimation.
9. What water quality and operational data should I collect during the evaluation phase?
At a minimum water quality and operational parameters should include typical parameters for filter evaluations (e.g., turbidity, headloss, temp, pH, alkalinity), target contaminants (e.g., TOC, manganese, iron, MIB, geosmin, micropollutants), nutrients (e.g., orthophosphate, ammonia) and biomass (e.g., adenosine triphosphate).
10. Are there regulatory guidelines available for developing an evaluation plan?
Regulatory guidelines vary from state to state. Please consult your primacy agency for pilot testing requirements.