Simulation on combined rapid gravity filtration and backwash models

Combined rapid gravity filtration and backwash models have been applied to simulate filtration and backwash cycles. The simulated results from the backwash model suggest that an optimum air flow rate exists to maximise particle removal efficiency in the backwash operation for a certain backwash system. The simulation of combined rapid gravity filtration and backwash models suggests that the filter should not be completely cleaned up in the backwash and a certain amount of particles retained on filter grains after backwash can be beneficial for subsequent filtration runs. This is consistent with the experimental results in the literature.

Simulation of combined rapid gravity filtration and backwash models

Combined rapid gravity filtration and backwash models are applied to simulate filtration and backwash cycles. The simulated results from the backwash model suggest that air flow rate can be optimised to maximise particle removal efficiency in the backwash for a particular system. The simulation of combined rapid gravity filtration and backwash models suggests that efficient backwash operation is essential for maintaining the life time of a filter. However, the filter is not advised to be completely cleaned up in the backwash and the particles retained on filter grains after the backwash can be beneficial for subsequent filtration runs.

The effect of polymeric flocculants on floc strength and filter performance

Polymeric flocculants are widely used throughout the water industry as flocculant aids, they are known to increase floc density and aid settlement in the clarification stage of the water treatment process. In this research, polymeric flocculants were used to improve floc strength prior to filtration on a dissolved air flotation (DAF) plant in an attempt to prevent filter breakthrough. A modified jar test procedure using a PDA (photometric dispersion analyser) optical flocculation monitor was developed in order to evaluate the system floc strength. Filtration trials were carried out on a pilot filter rig situated on a surface water treatment works in Yorkshire. The filter feed originated from the main plant filter channel. Filter performance was assessed by continuous online monitoring of effluent particle counts, turbidity and headloss over the period of the filter run. Results indicated that low doses of polymeric flocculants had a beneficial effect on filtered water quality, as measured by particle counts, turbidity, UV254 absorption and dissolved organic carbon (DOC). Polymeric flocculants also had the effect of extending filter run length. The modified jar test results indicated that the flocculants used improved the floc strength and enhanced reflocculation of the micro flocs present after the flotation process.