My GGA typically fails high, whats the problem?
High GGA generally means one of three things: • check to be sure that your GGA solution is not “bad” • there is too much seed or a very variable seed • there is overall contamination of the dilution water or glassware Typically, high GGA means contamination. You could be getting extra bugs from your dilution water adding to the depletion, but you should also see this in your dilution water blanks (exceeding 0.2 mg/L depletion). If this is happening, you’ll need to take corrective action with your water system. You may have contaminated your lot of GGA…try using a new lot. Remember that GGA failing high means more depletion than you would expect…this depletion may be coming from bugs you aren’t accounting for with seed controls, or some other BOD material “food” within the system.
