Solid-Liquid Separation Technology for Removing Contaminant Fines from Water Scrubbing, Clarifier Effluents and Grey Water

Treating water for environmental and process benefits is becoming more important in the oil and gas, energy, bioenergy, biochemical and chemical industries. As these operations are looking to become more cost efficient, water usage is being investigated. One critical aspect of these processes is the solid-liquid separation technology that is used to keep the water free of solid contaminant fines.

This paper discusses thin-cake candle filter technology as an alternative to filter presses and bag and filter cartridges for removing solid contaminant fines from the water streams. These contaminants originate from various sources and are generally less than 1 micron (um) in size, which makes their removal very difficult. Candle filter technology and the process of thin-cake building, is a new approach for high-efficiency and cost-effective fines removal.

The paper begins with the problem definition and a discussion of the bench-top laboratory tests that are conducted for problem analysis, process development, technology selection and scale-up. The tests include pressure, filter media, filter aids, and similar process parameters. The candle filter technology is examined for its ability to filter and dry the contaminants to meet the standards of non-hazardous and “no free liquid” for solids disposal. Cake washing is also discussed, as, in some cases, soluble or insoluble components or hazardous solvents must be removed from the solid cake prior to disposal. Three different case histories are presented for purge water treatment units using filter aids, concentration without filter aid, and grey water concentration. Finally, there is a discussion of the impacts of chemical usage in clarifiers on filtration efficiency and troubleshooting.