Environmental Engineering Reference
In-Depth Information
5. Determine the treatment evaluation criteria. See Section 3.1.2 for more detail on
parameters that are used in selecting a treatment method.
• Existing treatment processes
• Target inished water arsenic concentration—technically based local limits for
arsenic and TDS domestic waste discharge method
• Land availability
• Labor commitment
• Acceptable percent water loss
• Maximum source low rate
• Average source low rate
• State or primacy agency requirements that are more stringent than those of
t h e E PA
6. Select a mitigation strategy using the decision trees provided in Section 3.2. These
trees lead to the following mitigation strategies.
• Nontreatment and treatment minimization strategies source abandonment
− Seasonal use
− Blending before entry to distribution system
− Sidestream treatment
• Enhance existing treatment processes enhanced coagulation/iltration enhanced
lime softening
− Iron/manganese iltration
• Treatment (full stream or sidestream) ion exchange
− Activated alumina
− Iron-based sorbents: coagulation-assisted microiltration; coagulation-
assisted direct iltration oxidation/iltration
• Point-of-use treatment program activated alumina
− Iron-based sorbent
− Reverse osmosis
7. Estimate planning-level capital and operations and maintenance costs for the miti-
gation strategy using the costs curves provided in Section 4. Include costs for arse-
nic removal and waste handling. If this planning level cost is not within a range
that is inancially possible, consider using different preferences in the decision
trees.
8. Evaluate design considerations for the mitigation strategy. See Section 2.5 for
enhancing existing treatment processes and Sections 6 through 8 for the design of
new treatment processes.
9. Pilot the mitigation strategy. Although not explicitly discussed in this handbook,
piloting the mitigation strategy is a normal procedure to optimize treatment vari-
ables and avoid implementing a strategy that will not work for unforeseen rea-
sons. For many small systems, pilot testing may be performed by the vendor and
result in a guarantee from the vendor that the system will perform to.
10. Develop a construction-level cost estimate and plan.
