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Waste Treatment for the CIP System 317
system requires only connecting the drains from the skid and low points of the
circuit, to various floor drains.
Asmall quantity of new CIP systems are being installed in facilities that are
scaling up fromsmall processes that did not originally use CIP systems. These small
process volumes may not have required treatment before discharging to the city
(i.e., discharging within the “municipal discharge limits”). In this second scenario, it
is tempting to try to treat the waste stream from the CIP circuit on the skid before
discharging it down the drain. This approach is not recommended because it tends
to deposit what you just cleaned from process surfaces back on the equipment and
piping. The high pH that was so effective in breaking up the process residue loses its
ability to hold the residues in solution when the pH is adjusted in the circuit back
toward neutral.
In following the recommendation to send the CIP effluent to afacility-wide or
on-site waste treatment system, it will be necessary to connect all CIP systems to a
drain system. These process/CIP drain systems are similar to the gravity drain
systems for building plumbing but there are some significant differences. The key
aspects for consideration in the design of these process/CIP drain systems are as
follows:
1. Appropriate materials of construction must be used for the high purity (read:
“mineral hungry”) water as well as the acid wash; both at elevated temperatures.
The recommended materials include stainless steel or fiberglassreinforced
plastic for their corrosion resistance.
2. The equipment drains at the CIP skids should be appropriately oversized to
prevent flooding the floors around the skids during the pump-to-drain
sequences. It is also recommended to locate the skid in adiked containment
area or pan (Fig. 1).
3. Instantaneous flow rates must be used when sizing drains, branches, and
headers, not the average flow with usage factors, commonly used by plumbing
designers. Special consideration should be given to routing these branches and
headers directly to the waste treatment system without many turns.
4. As with the branches and headers, the vents from these high capacity drain
systems need to be appropriately sized and located with consideration for
plumbing codes as well as CIP flow rates.
5. Provision of an air break between the CIP skid and the floor drain to prevent
backing up waste into process systems (Fig. 2).
The oversized drain at the CIP skid discharge point should give consideration
to the following needs:
& Asuggested size of 10 in. diameter and 24 in. deep
& Located directly below CIP system drain
& Appropriate air gap to prevent back siphoning
& Debris strainer to catch large objects in containment pan
HOW DO ITREAT THE WASTEWATER ON-SITE?
The on-site waste treatment system will need to address treatment of flows that are
not within pH- and temperature-permitted ranges. The effluent from CIP systems
can also impact afacility’s ability to meet permit requirements for total phosphorus
and BOD concentrations.