Flocculent Treatment Management Plan
8.
Monitoring and maintenance
In addition to the Water Quality Discharge Monitoring Programme (WQDMP) (Section 9 of this FTMP), the following monitoring and maintenance specific to the flocculation management practices is required.
8.1 Monitoring Monitoring will include: • • • •
Certification of all ESC devices; Inspection after rainfall event; Weekly audits; and Pre and post rain event audits, including significant weather events.
The specific monitoring of the flocculation system will be undertaken by the Site Foremen and Site Engineers with regular checks of this monitoring made by the Environmental and Sustainability Manager. This monitoring will be undertaken weekly and following heavy rain events of the following items: • • • • • • • •
Rainfall in previous 24 hours; Depth of water in displacement tank; Volume of flocculent used (added); pH of the pond; Initial header tank level; Any changes in degree of stabilisation of the site; Appearance of pond (relative turbidity); and Estimated level of accumulated sediment within pond.
The frequency of this testing may be increased during extended periods of heavy rainfall or reduced during dry periods. Additionally, prior to any forecast heavy rain or if the site is to be unattended for more than 48 hours the flocculent reservoir tank will be filled to ensure that chemical treatment will occur through the following (or potential) 50mm of rainfall. The results of pH sampling will be used to determine if any modifications are required to the dosage rate. The acceptable limits for the pH is between 5.0 and 9.0. If the pH levels fall outside these ranges the Environmental and Sustainability Manager will determine appropriate actions which could include decommissioning the flocculation unit or adding alternate chemicals, such as sodium carbonate or sodium bi-sulphate, to alter the pH. Monitoring of pH will be a key indicator of the potential for residual aluminium discharges. Specifically, overdosing of PAC may cause a reduction in pH, raising the potential for aluminium within the PAC to react, forming toxic aluminium compounds that are bioavailable to fresh and marine water organisms.
8.2 Maintenance The Site Foreman will have responsibility for the maintenance of the chemical treatment devices on their site.
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