FIREFIGHTING WASTEWATER TREATMENT UTILISING POWDEREC ACTIVATED CARBON AND CERAMIC MEMBRANES

摘要

Firefighting wastewater is often highly polluted, with a combination of heavy metals, oils and grease, and surfactants used to produce foam. This presents a challenge to technologies typically used to treat the water to a standard suitable for water recycling. In this study, a robust process was trialled to treat the wastewater utilising the following steps: flocculation, ozone and powdered activated carbon, followed by ceramic membrane filtration. Ceramic membranes were selected to filter the hard powdered activated carbon particles at high water recovery. Laboratory-scale tests were first conducted on a 1,000L sample of firefighting wastewater to confirm operating parameters, including dose rates and likely fouling to be generated on the membrane. A continuously operating process was then trialled utilising 10,000L of wastewater having a COD reaching up to 5,000 mg/L towards the end of the testing. The pilot plant trial was operated for 10 days (1,000 L/day) with a view to optimising the operating conditions. The complete process saw turbidity reduced to values consistently below 1 NTU, while COD was within the range of 720 mg/L to 950 mg/L. The direct application of powdered activated carbon assisted the membrane by maintaining a stable flux and reducing the fouling rate - compared to running the membrane unit without the carbon dosing, which caused rapid fouling of the membrane that could not be restored with normal operation. This research has shown that a viable treatment process can be employed to adequately treat firefighting wastewater. Moreover, the trials have demonstrated a beneficial effect of the direct application of powdered activated carbon to ceramic membrane filtration in reducing the rate of fouling.