In pond waters, it has been observed that at pH values of about 2.5 or higher, algae becomes an issue.
Below this pH, algae is generally not a problem. Figure 3 shows the process flow of a temporary system
installed at Piney Point, an abandoned site that was under remediation by a court appointed receiver.
This 500‐gpm system included 400,000 gallon storage, bentonite clay feed, ballasted clarification to
remove the bulk of the suspended solids, dual stage media filtration for fine suspended solids removal
and two pass RO with inter‐stage pH adjustment and anti‐scalent. The pH adjustment is for ammonia
removal and the anti‐scalent controls precipitation on the second pass membranes caused by the
decreased solubility of some salts when the pH is increased. The final step in the process is ion
exchange resin that polishes the second pass product to remove low levels of ammonia. Although the
membrane process was capable of achieving the discharge specification of < 1PPM ammonia, the
practical limit of the process was about 0.7 PPM. As there was no retention between the system and
discharge directly to Bishops Harbor, it was felt that a polishing step to prevent an accidental discharge
of ammonia directly to the environment was appropriate.
In pond waters, it has been observed that at pH values of about 2.5 or higher, algae becomes an issue.Below this pH, algae is generally not a problem. Figure 3 shows the process flow of a temporary systeminstalled at Piney Point, an abandoned site that was under remediation by a court appointed receiver.This 500‐gpm system included 400,000 gallon storage, bentonite clay feed, ballasted clarification toremove the bulk of the suspended solids, dual stage media filtration for fine suspended solids removaland two pass RO with inter‐stage pH adjustment and anti‐scalent. The pH adjustment is for ammoniaremoval and the anti‐scalent controls precipitation on the second pass membranes caused by thedecreased solubility of some salts when the pH is increased. The final step in the process is ionexchange resin that polishes the second pass product to remove low levels of ammonia. Although themembrane process was capable of achieving the discharge specification of < 1PPM ammonia, thepractical limit of the process was about 0.7 PPM. As there was no retention between the system anddischarge directly to Bishops Harbor, it was felt that a polishing step to prevent an accidental dischargeof ammonia directly to the environment was appropriate.
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