Aquapure Troubleshooting part 3: Common upsets
Industrial manufactures use their wastewater treatment system to
treat things like metals, fats, oils and greases, odor and COD. These
systems can be very sensitive to any changes. When a problem occurs
in a wastewater line we usually recommend start at the discharge and
work backwards up the line.
Any of these problems look familiar?
4 of the most common WWT Problems for Industrial manufacturers.
Robin has outlined the first steps you should take if you have one of
these problems in your WWT system.
Upset - Floating floc in the clarifier:
 Check other chemistry to see if dosing is correct. The most
common problem we see is the addition of too much polymer to
the flocculation tank.
 Check the pH and ORP of the
water in the clarifier. If the ORP
is positive- possible residual
oxidizer needs to be reduced.
 Air from solids on the bottom
could be growing bacteria and
off-gassing, latching onto
particles. Correction would be to
blowdown the clarifier and add a
small amount of defoamer to the
clarifier or the premix tank.
 Check if the flow rate has
increased. If it has, it could be due to increased production not
giving enough time for the settling of solids.
Upset - Foam
 Check for any air lines bringing air into the system.
 Is there any bacterial growth? Excess foam can begin by growth
of bacteria from colloidal solids in slow moving rinses that let off
gas and rise to the surface leading to foam and odor.
 Check with production for
dumps. For example if there is a
cleaner dump (instead of a
bleed and feed) into a
continuous flow type system
the higher concentration
combined with the agitation
can create a lot of foam.
If foam is left untreated it can
increase and lead to inaccurate level
indicators in tanks creating false calls
for water or chemistry. It can also grow so much that it escapes the
tank- overflowing on the floor causing unsafe, slippery conditions.
Upset - Pin floc formation:
 Check the lines and pumps to the polymer
drum and make sure lines are not clogged.
Polymers have a shelf life once water has
been added. The harder the water - the
shorter the shelf life. Anionics last 1 month,
cationics last 1-2 days.
 Was the polymer “made down” correctly? If
there is residual diluted polymer left in the day tank- the
concentrate amount has to be adjusted down so as not to include
this in the calculation. The polymer needs to mix until
homogenous then the mixer should be turned off and allowed to
age for 30 minutes-1 hour for best activity. The mixer in the
premix tank should be slow with large paddles so as not to shear
the floc.
 Do some jar testing on the line to see if the water coming into the
system has enough contaminants to treat. If there is way less
metals then the treatment becomes more difficult or the
coagulant has to be boosted.
 Are you using the right polymer? There are many to choose from
through bench testing with your chemical provider. They will be
anionic, cationic or non-ionic.
Upset - Metals out of Compliance:
 Check the pH and ORP in the clarifier
water. It should be around 8.5-9.5. If it is
out of this range check your solubility
chart to make sure you are in the right pH
range.
 Go back to the EQ tank and check the lines
and dosing of the coagulant. Make sure
the drums are also pumping properly.
Then do some benchside jar testing by
bracketing the dosing of the coagulant – if you normally dose a 1
ml/gal then try ½ ml and 2-3 ml so you can see what an increase
or decrease in chemistry helps.
 Check with production on spent bath dumps or cleanouts, new
chemistry used and new jobs coming in. If a new metal shows up
find out why and the pH at which it is least soluble. If there a new
cleaner on the line that possibly has a chelator in it. You may
have use a metal precipitant in this case.