Advanced Treatment: MBR, GAC & RO

Quick Answer: MBR = biology + membranes. GAC = adsorption. RO = desalination/reuse.

Membrane Spectrum

MBR

Eliminates clarifier; higher MLSS; excellent effluent for reuse.

GAC

Freundlich/Langmuir isotherms; replace at breakthrough.

RO

Applied pressure must exceed osmotic pressure; concentrate disposal is key constraint.

Multi-Step Workflow

List givens with units, select the governing relationship, convert to a consistent unit set, solve, and compare to a rough estimate.

Advanced Treatment: MBR, GAC, RO

Design Cues

MBR replaces secondary clarifier; fouling and transmembrane pressure matter. RO requires pretreatment (antiscalant, cartridge filters) and produces concentrate brine that needs management. GAC breakthrough defines bed life — empty bed contact time (EBCT) appears in conceptual stems.

On the Exam: Match contaminant to process: pathogens → disinfection/UV; TDS → RO; dissolved organics → GAC; nutrients → biological BNR — not RO first for BOD.

Advanced Treatment: MBR, GAC, RO

Design Cues

MBR replaces secondary clarifier; fouling and transmembrane pressure matter. RO requires pretreatment (antiscalant, cartridge filters) and produces concentrate brine that needs management. GAC breakthrough defines bed life — empty bed contact time (EBCT) appears in conceptual stems.

On the Exam: Match contaminant to process: pathogens → disinfection/UV; TDS → RO; dissolved organics → GAC; nutrients → biological BNR — not RO first for BOD.

Advanced Treatment: MBR, GAC, RO

Design Cues

MBR replaces secondary clarifier; fouling and transmembrane pressure matter. RO requires pretreatment (antiscalant, cartridge filters) and produces concentrate brine that needs management. GAC breakthrough defines bed life — empty bed contact time (EBCT) appears in conceptual stems.

On the Exam: Match contaminant to process: pathogens → disinfection/UV; TDS → RO; dissolved organics → GAC; nutrients → biological BNR — not RO first for BOD.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

Additional review point: verify assumptions, boundary conditions, and whether the problem is steady-state or transient before selecting an answer.

MBR Flux and Fouling

Typical flux 15–25 L/m²·h; membrane cleaning (CIP) restores permeability. MLSS 8–12 g/L vs 3–5 in conventional AS.

GAC Breakthrough

EBCT 10–20 min for taste/odor; virgin vs reactivated carbon. Isotherm lab test sizes dose.

RO Recovery and Brine

50% recovery on seawater → concentrate 2× salinity — scaling limits (CaSO₄, silica). Antiscalant dosing required.

Energy Comparison

RO ~3–6 kWh/m³ seawater; MBR adds 0.5–1 kWh/m³ over conventional AS for air scour and pumping.

Worked Example

Feed TDS 35,000 mg/L, 50% recovery → permeate ~175 mg/L (99.5% rejection illustrative), concentrate ~70,000 mg/L — brine disposal cost drives feasibility.