Proceedings

Risk based site selection

Risk factors selected based on ‘available data’ for many sites

Identified Risk Factors and Assigned Significance:

Highly significant (Weighting = 3)

• High FE nitrite (L<0.5 mg/l, H>1.5 mg/l)
• High sludge age (carbonaceous ASPs only) (L<5, H>10 days)
• Ammonia failure status (L = No, H = Yes)

Very significant (Weighting = 2)

• Capacity utilisation % (L<80%, H>110%)
• Low ammonia consent (L>16mg/l, H<5 mg/l)
• Absolute difference of influent and consent ammonia (L<5mg/l, H>15mg/l)
• Ratio of 95%ile : average effluent ammonia (L<1.5, H>3.5)

Significant (Weighting = 1)

• BOD failure status (L = No, H = Yes)
• Low BOD consent (L>25 mg/l, H<15 mg/l)
• Presence of STC liquor returns and / or AD(0 = WWTWL= Non-AD STCM = Digestion indigenous only H = Digestion with imports)