Water Treatment Plant
Engineering Calculator

The complete engineering reference for water treatment plant design and operations. All major calculation modules covering RO membranes, gravity clarification, ion exchange demineralization, boiler feed water chemistry, potable water treatment, and chemical dosing — with correct ASME, IS, WHO and ABMA standards built-in.

🌊

Raw Water

River, bore-well, sea, municipal

🟤

Clarifier

Coagulation, settling, sludge

🔲

DMF/ACF

Dual media, carbon filtration

🔵

RO Unit

Membranes, recovery, rejection

🟢

DM Plant

Cation, anion, mixed bed

🔥

Boiler

Steam generation, blowdown

Module 01

RO System Design

Recovery · Flux · TDS rejection · Salt passage · LSI · Osmotic pressure · Membrane sizing · SEC · SDI assessment

Module 02

Clarifier Design

SOR · Detention time · Weir loading · Tank dims · Sludge volume · Coagulant dose · G-value · Upflow velocity

Module 03

DM Plant

Resin volume · Exchange capacity · HCl/NaOH regen · Cycle length · Conductivity · Silica leakage · Degasser

Module 04

Boiler Feed Water

COC · Blowdown · Makeup flow · O₂ scavenger · Scale limits (ASME/IS/ABMA) · Silica carryover · Steam purity · Heat loss

Module 05

Drinking Water

Cl₂ residual · CT value · Giardia log removal · Filtration area · IS 10500 compliance · LSI · RSI corrosion index

Module 06

Chemical Dosing

Pump sizing · Tank volume · 3-chemical system · Safety factor · Daily consumption · Stock solution

🔵

RO System DesignRecovery, flux, TDS rejection, LSI, membrane sizing

📥 Feed Water

Feed Flow Rate

m³/hr

Feed TDS

mg/L

Feed Pressure

bar

Feed Temperature

°C

SDI (Silt Density Index)

SDI

Feed Conductivity

µS/cm

⚙ System Design

Target Recovery Rate

Membrane Salt Rejection

Flux Rate

L/m²/h

No. of Stages

stages

Membrane Active Area

m²/elem

Elements per Vessel

elem

🔬 Water Chemistry (LSI)

Feed pH

Ca²⁺ Hardness

mg/L

Total Alkalinity

mg/L

⚠

🔵

RO Results

Fill parameters and calculate

Computing RO system…

🟤

Clarifier DesignSOR, detention time, weir loading, tank sizing

💧 Flow & Raw Water

Design Flow Rate Q

m³/hr

Raw Turbidity In

NTU

Target Effluent NTU

NTU

Suspended Solids (SS)

mg/L

Water Temperature

°C

Feed pH

🏗 Design Parameters

Surface Overflow Rate (SOR)

m/hr

Detention Time

Weir Loading Rate

m³/m/d

Clarifier Type

Sludge Volume Index (SVI)

mL/g

MLSS Concentration

mg/L

🧪 Coagulation

Coagulant Type

Coagulant Dose

mg/L

⚠

🟤

Clarifier Results

Fill design parameters and calculate

Sizing clarifier…

🟢

DM Plant DesignIon exchange, resin sizing, regeneration chemicals

💧 Feed Water Ion Analysis

Feed Flow to DM

m³/hr

Total Cations (as CaCO₃)

mg/L

Total Anions (as CaCO₃)

mg/L

Silica (SiO₂)

mg/L

Free CO₂

mg/L

Feed TDS

mg/L

⚗ Resin & Column Design

Cation Resin Capacity

eq/L

Anion Resin Capacity

eq/L

Target Cycle Length

Service Flow Velocity

m/hr

Resin Bed Height

🧪 Regeneration Design

HCl Solution Conc.

% w/w

NaOH Solution Conc.

% w/w

HCl Dose (per eq resin)

g/eq

NaOH Dose (per eq resin)

g/eq

🎯 Quality Targets

Target Conductivity

µS/cm

Target Silica (SiO₂)

mg/L

⚠

🟢

DM Plant Results

Fill parameters and calculate

Computing DM design…

🔥

Boiler Feed Water QualityASME CRTD-34 · IS 10392 · ABMA — Complete analysis

🔥 Boiler Operating Conditions

Steam Generation Rate

t/hr

Drum Operating Pressure

bar(g)

Boiler Type

Condensate Return %

No. of Boilers

nos.

Fuel Type

🌡 Makeup Water Quality (Feed to Boiler)

Makeup Water TDS

mg/L

Total Hardness (as CaCO₃)

mg/L

Total Alkalinity (as CaCO₃)

mg/L

Chlorides (Cl⁻)

mg/L

Silica (SiO₂)

mg/L

Iron (Fe total)

mg/L

Copper (Cu total)

mg/L

Dissolved O₂ (before DA)

mg/L

TOC (Total Organic Carbon)

mg/L

Oil/Grease

mg/L

💊 Chemical Treatment

O₂ Scavenger Chemical

O₂ Scavenger Excess %

pH Control Chemical

Target Boiler Water pH

Phosphate Dose (PO₄)

mg/L

Deaerator Present?

⚡ Limits Selection

Standard to Check Against

Max Allowable Boiler TDS

mg/L

⚠

🔥

Boiler Feed Results

Enter all operating parameters then calculate

Running boiler analysis…

🚰

Drinking Water TreatmentChlorination, filtration, IS 10500 compliance

💧 Raw Water Quality

Design Flow

m³/hr

Raw Turbidity

NTU

Raw TDS

mg/L

Raw pH

Total Hardness (as CaCO₃)

mg/L

Coliform (MPN/100mL)

MPN

Fluoride (F)

mg/L

Iron (Fe)

mg/L

⚗ Treatment Design

Alum Coagulant Dose

mg/L

Chlorine Dose Applied

mg/L

Chlorine Demand of Water

mg/L

Contact Time (CT)

min

Filtration Rate

m/hr

No. of Filter Beds

nos.

Filter Media Depth

Water Temperature

°C

⚠

🚰

Drinking Water Results

Fill parameters and calculate

Checking compliance…

🧪

Chemical Dosing SystemPump sizing, tank volume, daily consumption

💧 Process Flow

Process Flow Rate

m³/hr

Operating Hours/Day

hr/d

Tank Autonomy

days

Pump Safety Factor

🧪 Chemical 1 — Coagulant/Antiscalant

Chemical 1 Name

Dose

mg/L

Solution Strength

% w/v

Solution Density

kg/L

🧪 Chemical 2 — pH Adjustment

Chemical 2 Name

Dose

mg/L

Solution Strength

% w/v

Solution Density

kg/L

🧪 Chemical 3 — Disinfectant (NaOCl/Cl₂)

Chemical 3 Name

Dose

mg/L

Solution Strength

% w/v

Solution Density

kg/L

⚠

🧪

Chemical Dosing Results

Fill parameters and calculate

Sizing dosing system…

📋

Boiler Feed Water — ASME CRTD-34 StandardsIndustrial Watertube, High Duty, Drum Type — Official limits by drum pressure

📌 Source

ASME Consensus on Operating Practices for the Control of Feedwater & Boiler Water Chemistry in Modern Industrial Boilers (CRTD Vol. 34). These are the globally recognised standard for watertube boilers. For fire tube boilers, limits may be relaxed by 20-30% at equivalent pressures.

🔥 Drum-type Boiler Water Quality Limits (ASME CRTD-34 / ABMA)

Parameter	0–300 psig (0–21 bar)	301–450 psig (21–32 bar)	451–600 psig (32–41 bar)	601–750 psig (41–52 bar)	751–900 psig (52–62 bar)	901–1000 psig (62–69 bar)	1001–1500 psig (69–103 bar)	1501–2000 psig (103–138 bar)	OTSG / >2000 psig
Boiler Water TDS max (mg/L)	700–3500	600–3000	500–2500	200–1000	150–750	125–625	100	50	0.05
Conductivity max (µS/cm)	1100–5400	900–4600	800–3800	300–1500	200–1200	200–1000	150	80	0.15–0.25
Total Alkalinity max (mg/L)	700	600	500	400	300	200	NS	NS	NS
Silica max (mg/L SiO₂)	150	90	40	30	20	8	2	1	0.02
Suspended Solids max (mg/L)	15	10	8	3	2	1	1	NS	NS
Steam Purity (TDS max, mg/L)	0.2–1.0	0.2–1.0	0.2–1.0	0.1–0.5	0.1–0.5	0.1–0.5	0.1	0.05	0.05
Boiler Water pH	10.5–12.0	10.5–11.8	10.0–11.8	10.0–11.5	9.8–11.0	9.6–10.8	9.0–10.0	8.5–9.5	VAM

📋 Feedwater Quality Limits (ASME CRTD-34) — Water entering boiler

Feedwater Parameter	0–300 psig	301–600 psig	601–1000 psig	1001–1500 psig	1501–2000 psig	Notes
Iron, Fe (µg/L)	100	50	25	10	5	As total iron
Copper, Cu (µg/L)	50	25	20	10	3	As total copper
Total Hardness (µg/L)	≈0 (trace)	ND	ND	ND	ND	As CaCO₃ equivalent
pH at 25°C	7.5–10	7.5–10	8.0–9.5	8.5–9.5	9.0–9.5	Adjusted for corrosion control
Dissolved O₂ (µg/L)	≤7000 (7 ppm)	≤1000	≤100	≤20	≤7	After deaerator
Silica, SiO₂ (mg/L)	≤150	≤40	≤10	≤2	≤1	For turbine protection
TOC (mg/L)	<10	<5	<3	<1	<0.5	Non-volatile organic carbon
Oil/Grease (mg/L)	<1.0	<0.5	<0.5	<0.1	<0.05	Causes foam/carryover

⚠ Critical Notes

NS = Not Specified; ND = Not Detectable; VAM = Use only Volatile Alkaline Materials
For boilers with superheaters or turbine drives, apply values for at least the next higher pressure range
With local heat fluxes >150 kW/m², use values for the next higher pressure range
Alkalinity values >10% of conductance value may cause foaming and carryover
If makeup is DM quality, conductivity for <1000 psig may use the 1000–1500 psig table values
Silica carryover to turbine blades becomes critical above 600 psig — strictly control boiler silica
OTSG (Once-Through Steam Generators) have essentially zero tolerance for impurities

🇮🇳

IS 10392 — Boiler WaterBureau of Indian Standards

Parameter	<20 bar	20–60 bar	>60 bar
pH	8.5–9.0	8.8–9.2	9.0–9.5
Hardness (ppm)	≤5	≤1	Nil
TDS (mg/L)	≤3500	≤2000	≤500
Silica (mg/L)	≤25	≤10	≤2
Dissolved O₂	≤0.1	≤0.02	Nil
Conductivity (µS/cm)	≤6000	≤4000	≤2000
Total Alkalinity	≤700	≤500	≤300
Chlorides (mg/L)	≤150	≤75	≤30
Iron (mg/L)	≤2	≤0.5	≤0.1

🚰

IS 10500:2012 — Drinking WaterBIS Standard

Parameter	Acceptable	Max Perm.
pH	6.5–8.5	No relaxation
TDS (mg/L)	≤500	2000
Turbidity (NTU)	≤1	5
Hardness (mg/L)	≤200	600
Chloride (mg/L)	≤250	1000
Fluoride (mg/L)	≤1.0	1.5
Iron (mg/L)	≤0.3	—
Nitrate (mg/L)	≤45	—
Residual Cl₂	0.2–1.0	—
Coliform/100mL	Nil	—

🟢

DM Water StandardsIon exchange product quality

Parameter	DM (Two-bed)	Mixed Bed
Conductivity	<10 µS/cm	<0.1 µS/cm
Silica (SiO₂)	<0.1 mg/L	<0.02 mg/L
pH	6.8–7.2	7.0±0.1
TDS (mg/L)	<5	<0.1
Hardness	Nil	Nil
Sodium (Na)	<0.1 ppm	<0.01 ppm
Resistivity	>0.1 MΩ·cm	>10 MΩ·cm

🔵

RO Design Criteria & Key FormulasQuick engineering reference

🔵 RO Design Ranges

Brackish recovery: 70–80%
Seawater recovery: 35–50%
Flux (brackish): 14–20 L/m²/h
Flux (seawater): 10–14 L/m²/h
SDI feed limit: ≤5, ideal <3
Salt rejection: 96–99.8%
LSI concentrate: <+1.0 (scaling)

🟤 Clarifier Design

SOR: 0.8–2.0 m/hr (gravity)
Detention time: 2–4 hours
Weir loading: 125–250 m³/m/day
Flocculation G: 20–60 /s
Rapid mix G: 600–1000 /s
Inclined plate SOR: 5–8× plain

🟢 DM Plant Design

Service velocity: 10–20 m/hr
Cation capacity: 1.7–2.1 eq/L
Anion capacity: 1.0–1.4 eq/L
HCl dose: 90–110 g/eq resin
NaOH dose: 100–130 g/eq
Regen freq: <2/day ideal

🔣 Key Formulas

/* RO */
Recovery R = Qp/Qf × 100
TDS_perm = TDS_feed × (1-rej)
TDS_conc = (TDS_f×Qf - TDS_p×Qp)/Qc
CF = 1/(1-R)
SEC = P×Qf/(3600×0.75×Qp) kWh/m³
/* LSI */
LSI = pH - pHs
pHs = pK2-pKs+p[Ca]+p[Alk]

/* Clarifier */
SOR = Q/A (m/hr)
Area = Q/SOR (m²)
Volume = Q × HRT (m³)
Weir = Q_daily/WLR (m)
/* DM Plant */
Resin Vol = Flow×Cycle×Load/Cap
HCl L/regen = eq×dose/(Conc×density)
Cycle hr = (Vol×Cap)/(Load×Flow×1000)

/* Boiler Feed Water */
COC = TDS_boiler / TDS_makeup
BD% = 1/(COC-1) × 100
BD_flow = Steam × BD%/100
Makeup = Steam × (1-CR + BD%/100)
Silica_boiler = Si_feed × COC
/* Heat loss */
Q_BD = BD_flow × h_f (kW)

Water Treatment PlantEngineering Calculator

RO Results

Clarifier Results

DM Plant Results

Boiler Feed Results

Drinking Water Results

Chemical Dosing Results

🔗 Share WTP-Pro

Water Treatment Plant
Engineering Calculator