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Category Engineering Calculators

Project Parameters Configure plant specifications

Configuration Preset

Target Capacity (m³/day)

Small MuniMega Plant

Desalination Technology

Feed TDS (mg/L)

Temp (°C)

Energy Cost ($/kWh)

Grid Carbon Intensity (kg/kWh)

Chemical/Maint Factor (% of OpEx)

25%

          LCOW (Unit Cost)
          $--
          per cubic meter
        

Daily OPEX $--

Spec. Energy -- kWh/m³

CO₂ Footprint -- tons/yr

Cost Composition

Energy

$0.00

CAPEX

$0.00

Chem/Labor

$0.00

Environmental Impact

Brine Salinity -- mg/L

Brine Volume -- m³/day

Recovery Rate -- %

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About

The economic feasibility of desalination projects hinges on the Levelized Cost of Water (LCOW), a metric sensitive to thermodynamic limits, local energy tariffs, and raw water chemistry. Unlike basic estimators, this tool accounts for the Osmotic Pressure variations caused by Feed Water Salinity (TDS) and Temperature. A 1,000 ppm increase in salinity or a 5°C drop in temperature can significantly alter the pump pressure required to overcome the osmotic barrier.

Industrial plants must balance High-Pressure Pump (HPP) energy consumption against membrane replacement schedules and chemical cleaning (CIP) costs. Thermal methods like Multi-Stage Flash (MSF) offer robustness against algae blooms but suffer from high specific energy consumption unless paired with cogeneration power plants.

This calculator provides a breakdown of CAPEX (amortized infrastructure) vs. OPEX (Variable: Energy, Chemicals; Fixed: Labor, Maintenance). It also computes the Concentration Factor to estimate the salinity of discharge brine, a critical parameter for Environmental Impact Assessments (EIA) in protected marine zones.

Formulas

The core calculation for Osmotic Pressure (Π), which drives energy consumption in RO, is derived from the Van 't Hoff equation approximation:

{

Π ≈ i × M × R × TE_specific ≈ Πη_pump × R_ecovery + E_aux

Where M is molarity (derived from TDS), T is absolute temperature (K), and η_pump is the efficiency of the High-Pressure Pump (typically 0.85). The Brine Salinity (S_brine) is calculated via mass balance:

S_brine = S_feed1 − R_ecovery

Reference Data

Technology	Feed Source	TDS Range mg/L	Specific Energy kWh/m³	Typical Recovery %	LCOW Range $/m³	CO₂ Intensity kg/m³
SWRO (Seawater RO)	Ocean	30,000 - 45,000	3.0 - 4.5	40 - 50	0.70 - 1.40	1.4 - 2.8
BWRO (Brackish RO)	Aquifer/Estuary	1,000 - 10,000	0.8 - 1.5	75 - 85	0.25 - 0.60	0.4 - 0.8
MSF (Multi-Stage Flash)	Ocean (High Salinity)	35,000 - 50,000	12.0 - 18.0	25 - 35	1.10 - 1.90	8.0 - 12.0
MED (Multi-Effect Dist.)	Ocean	35,000 - 45,000	6.0 - 10.0	30 - 40	0.90 - 1.50	4.0 - 8.0
MED-TVC (Thermal Vapor)	Ocean	35,000 - 45,000	5.0 - 8.0	30 - 45	0.85 - 1.40	3.5 - 6.0
ED/EDR (Electrodialysis)	Brackish	1,000 - 5,000	0.5 - 2.5	85 - 95	0.30 - 0.70	0.3 - 1.0
FO (Forward Osmosis)	High Fouling	Variable	2.0 - 4.0	30 - 60	Emerging	Low
MVR (Mech. Vapor Recomp.)	Industrial Waste	10,000 - 100,000	8.0 - 30.0	90 - 95	2.50 - 6.00	5.0 - 15.0

Frequently Asked Questions

Temperature has an inverse relationship with viscosity and osmotic pressure. In Reverse Osmosis (RO), colder water increases viscosity, requiring higher pump pressure to push water through membranes, thus raising energy costs. However, very high temperatures (above 35-40°C) can degrade polymer membranes, necessitating cooling or alternative thermal methods.

SWRO (Reverse Osmosis) is generally cheaper ($0.70-$1.20/m³) and less energy-intensive electrically. Thermal methods like MSF ($1.20-$2.00/m³) are energy hogs but are preferred in the Middle East where waste heat from power generation is available and the water has high salinity/bio-fouling potential that would clog RO membranes quickly.

Specific Energy is the energy required to produce one cubic meter of fresh water (kWh/m³). Modern SWRO plants with Energy Recovery Devices (ERDs) achieve 3.0-3.5 kWh/m³. Older plants or those without ERDs may use 5.0-8.0 kWh/m³. Thermal plants use equivalent thermal energy often exceeding 10-15 kWh/m³ equivalent.

Boron exists in seawater and is difficult to remove at standard neutral pH. Agriculture (especially citrus crops) requires very low boron levels (<0.5 mg/L). Achieving this often requires a "second pass" RO system or pH adjustment (alkalization), increasing both CAPEX and chemical costs.

The footprint depends on the grid's carbon intensity. If a grid emits 0.5 kg CO2/kWh and the plant uses 3.5 kWh/m³, the water footprint is 1.75 kg CO2/m³. Using solar or nuclear energy can bring this near zero, though construction emissions (concrete/steel) remain.