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Questions and Answers
What is the primary purpose of tertiary treatment?
Improve water quality
Which are common materials used in tertiary treatment?
Granular filtration is used when the effluent limit for total suspended solids (TSS) is greater than 10 mg/L.
False
Denitrification converts nitrate into ______ gas.
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Match the tertiary treatment process with its description:
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What is the key difference between a deep-bed down-flow filter and a conventional down-flow filter?
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Which type of filter introduces wastewater at the bottom and allows it to flow upward through sand bed?
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In a pulsed-bed filter, air pulses are used to disrupt the sand surface and allow penetration of suspended solids into the filter bed.
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The travelling-bridge filter is a proprietary continuous down-flow, automatic backwash, low-head, granular medium depth filter divided horizontally into long independent filter cells, each containing approximately ___ mm of medium.
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What is a membrane?
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Study Notes
Tertiary Treatment
- Removes phosphates and nitrates from wastewater
- Substances like activated carbon and sand are used
- Part of the treatment process before wastewater is discharged into the environment
- Improves water quality
Advanced Wastewater Treatment
- Includes technologies that treat water for reuse
- Employed to meet water quality requirements
- Examples include air stripping, ion exchange, NF or RO treatment
Why Tertiary Treatment?
- To remove total suspended solids and organic matter
- To remove specific organic and inorganic constituents
- To make treated wastewater suitable for land application or direct discharge
- To remove residual nutrients
- To remove pathogens from secondary treated effluent
- To reduce total dissolved solids (TDS) from secondary treated effluent
- To overcome increasing population pressures
Tertiary Treatment Processes
- Chemical precipitation: used to remove phosphorus
- Membrane filtration: used to remove suspended solids and organic matter
- Carbon adsorption: used to remove refractory organics
- Granular filtration: used to remove total suspended solids (TSS)
Denitrification Filters
- Used to remove nitrates from wastewater
- Denitrification converts nitrates into nitrogen gas
- The filter operates anaerobically
- Requires backwashing to release nitrogen
Filtration
- Mechanical, physical, or biological operation to separate solids from fluids
- Examples: HEPA filters, belt filters, horizontal plate filters, Büchner funnel
- Used in various applications: air conditioning, mining, furnaces, laboratories, aquariums
Water Filtration
- Removes impurities from water using a physical barrier, chemical process, or biological process
- Methods: conventional filtration, granular filtration, membrane filtration
- Used for agricultural irrigation, drinking water, aquariums, and swimming pools
Granular Filtration
- Used to remove suspended solids and organic matter
- Filter technologies: conventional down-flow filters, deep-bed down-flow filters, deep-bed up-flow continuous-backwash filters, pulsed-bed filters, traveling-bridge filters
Membrane Filtration
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Used to remove suspended solids and organic matter
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Membrane properties: sieving and diffusion mechanisms
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Types: microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), nanofiltration (NF)
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Used for tertiary treatment, water recycling, and wastewater treatment### Membrane Technology in Wastewater Treatment
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Membrane technology removes pollutants from wastewater through various processes.
Types of Membrane Filtration
- Microfiltration (MF) removes suspended solids, including microorganisms.
- Ultrafiltration (UF) removes large, dissolved solute molecules and suspended colloidal particles.
- Nanofiltration (NF) selectively removes multivalent ions and certain charged or polar molecules.
- Reverse osmosis (RO) removes inorganic ions.
- Electrodialysis (ED) and dialysis selectively extract ions from water and/or concentrate them in the waste stream.
- Pervaporation (PV) selectively extracts molecular gas and/or volatile solutes.
- Gas transfer (GT) transfers molecular gas into or out of water.
Increasing Efficiency through Filtration
- Sequencing filters from large to small pore size can decrease fouling.
- Filters must still be cleaned regularly to remain usable.
Properties of an Ideal Membrane
- An ideal membrane should have reasonable mechanical strength, high throughput, and be selective for the desired permeate constituent.
- It should also have high porosity, a thin layer of material, and a narrow range of pore size.
Driving Forces of Membrane Technology
- Driving forces make mass transfer through the membrane possible, including pressure difference (∆P), concentration difference (∆c), and electrical potential difference (∆E).
- Membranes can be classified according to their driving forces:
- Pressure difference (∆P): Microfiltration, Ultrafiltration, Nanofiltration, Reverse osmosis
- Concentration difference (∆c): Pervaporation, Gas separation, Vapour permeation
- Electrical potential difference (∆E): Electrodialysis, Electro-osmosis, Membrane electrolysis
- Temperature difference (∆T): Thermo-osmosis, Membrane distillation
Classification of Membranes according to Driving Force
- Reverse osmosis (RO): 225- 1000 psi (about 10- 60 bar)
- Nanofiltration (NF): 50- 300 psi (about 3-15 bar)
- Ultrafiltration (UF): 20- 100 psi (about 1-5 bar)
- Microfiltration (MF): 0.5 mm
Membranes Configuration
- Hollow fiber membrane: The modules contain several small (0.6 to 2 mm diameter) tubes or fibers.
- The feed solution flows through the open cores of the fibers and the permeate is collected in the cartridge area surrounding the fibers.
- The filtration can be carried out either “inside-out” or “outside-in”
- Mostly used in MF & UF
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Description
Quiz on advanced topics in hydrogeology and environmental science, covering tertiary and advanced sewage treatment, filtration, industrial waste water treatment, and solid waste management.
