# How to Write a Design Basis for Effluent Treatment Plants (ETP), LTDS Bio-Plants, MVRE & ZLD in Chemical & Pharma: A 500 KL Case Study

# Executive Summary & Technical Scope

In pharmaceutical Active Pharmaceutical Ingredient (API) synthesis, fine chemical batch manufacturing, and specialty chemical facilities, environmental compliance is a critical prerequisite for license-to-operate. Regulators worldwide—such as the Central Pollution Control Board (CPCB) in India, State Pollution Control Boards (SPCB), and the US Environmental Protection Agency (US-EPA under 40 CFR Part 439)—have mandated stringent discharge norms. For Red Category chemical and API industrial complexes, Zero Liquid Discharge (ZLD) combined with Low TDS Biological ETP (LTDS Bio-ETP), High-Recovery Reverse Osmosis (RO), and Mechanical Vapor Recompression Evaporators (MVRE) is frequently statutory, prohibiting untreated liquid waste discharge outside factory battery limits.

Executing an ETP or ZLD capital engineering project without a robust, audit-ready Basis of Design (BOD) or Design Basis Report (DBR) inevitably leads to catastrophic operational failures: biomass poisoning from solvent shock loads, osmotic plasmolysis in biological aeration tanks due to high salinity, severe scaling in Multiple Effect Evaporators (MEE), undersized aeration blowers, premature membrane fouling in Reverse Osmosis (RO), or massive CAPEX/OPEX overruns.

This comprehensive chemical and environmental engineering masterwork provides:

Full Flowsheet Architecture & Block Flow Diagram (BFD) spanning LTDS Bio-Treatment, Ultrafiltration (UF), High-Recovery RO, HTDS Solvent Stripping, MVRE, and ATFD Salt Crystallization.
Unit Operation Separation & Removal Efficiency Matrix (% removal of TSS, BOD, COD, TDS, Oil & Grease across every barrier).
Exhaustive Tank Sizing Table for a 500 KL Reactor Volume API Complex (250 m³/day Capacity) with exact dimensions, liquid depths, retention times (HRT/SRT), and Materials of Construction (MOC).
Complete Plant Utility & Power Connected Load Summary (Pump kW ratings, air blower CFM, steam consumption, chemical dosing kg/day).
RO Design in LTDS (2-stage array configuration, operating flux, feed pressure, salt rejection, $85\%$ recovery).
Mechanical Vapor Recompression Evaporator (MVRE) Sizing for RO Reject & HTDS Water (Compressor kW, vapor temperature rise, specific energy $\text{kWh/m}^3$ , thermal mass balance).
Statutory CPCB Discharge Standards vs. ZLD Plant Reuse Specifications Table.
An Industry-Standard 8-Section DBR Template & Checklist.

# 1. Complete Flowsheet Architecture & Block Flow Diagram (BFD)

A compliant chemical/pharma ETP/ZLD complex consists of three integrated treatment lines:

Line 1: LTDS Biological & Membrane Line (Process washes + Utility blowdown $\rightarrow$ Biological degradation $\rightarrow$ RO Water Recovery).
Line 2: HTDS & RO Reject Thermal Line (Mother Liquors + RO Reject $\rightarrow$ Stripper $
ightarrow $MVRE$
ightarrow $ATFD Salt Recovery). * **Line 3: Sludge Dewatering Line** (Primary DAF Sludge + Biological WAS$
ightarrow $Multi-Disc Screw Press$
ightarrow$ Dry Cake to TSDF).

                                      500 KL API MANUFACTURING FACILITY 
                                           (250 m³/day Raw Effluent)
                                                       │
        ┌──────────────────────────────────────────────┼──────────────────────────────────────────────┐
        │                                              │                                              │
        ▼                                              ▼                                              ▼
  STREAM A: HTDS / High COD                      STREAM B: LTDS Process Wash                    STREAM C: Utility Blowdown
  (35 m³/day | COD: 48k | TDS: 62k)             (140 m³/day | COD: 4.2k | TDS: 2.4k)            (75 m³/day | COD: 120 | TDS: 1.8k)
        │                                              │                                              │
        ▼                                              ▼                                              │
  ┌───────────┐                                  ┌───────────┐                                        │
  │ Solvent   │ (Recovered Solvents)             │ CPI / TPI │ (Free Oil Removed)                 │
  │ Stripper  ├────────────────► Tank Farm       │ Oil Trap  │                                        │
  └─────┬─────┘                                  └─────┬─────┘                                        │
        │                                              │                                              │
        │                                              ▼                                              │
        │                                        ┌───────────┐                                        │
        │                                        │ Primary   │ (Colloidal Solids)                     │
        │                                        │ DAF Unit  ├───────────────────┐                    │
        │                                        └─────┬─────┘                   │                    │
        │                                              │                         │                    │
        │                                              ▼                         │                    │
        │                                        ┌───────────┐                   │                    │
        │                                        │  Anoxic   │ (Denitrification) │                    │
        │                                        │   Tank    │                   │                    │
        │                                        └─────┬─────┘                   │                    │
        │                                              │                         │                    │
        │                                              ▼                         │                    │
        │                                        ┌───────────┐                   │                    │
        │                                        │ MBR Aerobic│                  │                    │
        │                                        │ Aeration  │                   │                    │
        │                                        └─────┬─────┘                   │                    │
        │                                              │                         │                    │
        │                                              ▼                         │                    │
        │                                        ┌───────────┐                   │                    │
        │                                        │ Submerged │ (Waste Sludge WAS)│                    │
        │                                        │ UF MBR    ├───────────────────┼───────────┐        │
        │                                        └─────┬─────┘                   │           │        │
        │                                              │ (MBR Permeate)          │           │        │
        │                                              │ (140 m³/day)            │           │        │
        │                                              ▼                         │           │        │
        │                                        ┌───────────┐                   │           │        │
        │                                        │ Combined  │◄──────────────────┼───────────┼────────┘
        │                                        │ RO Feed   │                   │           │
        │                                        └─────┬─────┘                   │           │
        │                                              │ (215 m³/day)            │           │
        │                                              ▼                         │           │
        │                                        ┌───────────┐                   │           │
        │                                        │ 2-Stage   ├───────────────────┼───────────┼────────► RO Permeate Recycled (182.75 m³/day)
        │                                        │ High RO   │ (85% Recovery)    │           │          (Cooling Tower / Utility Reuse - 73.1%)
        │                                        └─────┬─────┘                   │           │
        │                                              │ (RO Reject: 32.25 m³/day)│           │
        │                                              │ (TDS: 14,550 mg/L)      │           │
        │                                              ▼                         │           │
        └─────────────────────────────────────────────►│                         │           │
                                                       ▼                         │           │
                                                 ┌───────────┐                   │           │
                                                 │ MVRE Feed │                   │           │
                                                 │ Equalizer │                   │           │
                                                 └─────┬─────┘                   │           │
                                                       │ (67.25 m³/day)          │           │
                                                       ▼                         │           │
                                                 ┌───────────┐                   │           │
                                                 │   MVRE    ├───────────────────┼───────────┼────────► MVRE Condensate Recycled (59.72 m³/day)
                                                 │Evaporator │ (88.8% Recovery)  │           │          (Process Washes / Boiler Feed - 23.9%)
                                                 └─────┬─────┘                   │           │
                                                       │ (Concentrated Slurry)   │           │
                                                       ▼                         │           │
                                                 ┌───────────┐                   │           │
                                                 │   ATFD    │                   │           │
                                                 │ Dryer     │                   │           │
                                                 └─────┬─────┘                   │           │
                                                       │                         │           │
                                                       ▼                         ▼           ▼
                                                 ┌───────────┐             ┌───────────────────┐
                                                 │ Dry Salt  │             │ Multi-Disc Screw  │
                                                 │ Cake      │             │ Sludge Press      │
                                                 └─────┬─────┘             └─────────┬─────────┘
                                                       │ (2.93 MT/day)               │ (Dry Sludge Cake)
                                                       ▼                             ▼
                                           ┌───────────────────────────────────────────────┐
                                           │ AUTHORIZED TSDF HAZARDOUS WASTE LANDFILL SITE │
                                           └───────────────────────────────────────────────┘

# 2. Unit Operation Separation & Removal Efficiency Matrix

To prove mathematical compliance in the DBR, tabularize pollutant removal efficiencies across each physical, biological, membrane, and thermal barrier:

Unit Operation	Influent Streams	Target Pollutants	Inlet Conc.	Outlet Conc.	Removal Efficiency (%)	Operating Mechanism
Bar Screen & Grit Pit	Raw LTDS / HTDS	Floating debris, grit	$>500\text{ mg/L}$	$<350\text{ mg/L}$	$30\%$ TSS	Mechanical bar screening
CPI / TPI Oil Trap	Stream B Process Washes	Free Oil & Grease	$150\text{ mg/L}$	$<15\text{ mg/L}$	$90\%$ O&G	Coalescing plate gravity separation
Primary DAF Unit	Post CPI Effluent	Emulsified O&G, TSS	$350\text{ mg/L TSS}$	$<50\text{ mg/L TSS}$	$85.7\%$ TSS, $30\%$ COD	Microbubble flotation + Coagulant/Poly
Anoxic Denitrifier	Post DAF + MBR Recycle	Nitrate-Nitrogen ( $NO_3-N$ )	$45\text{ mg/L}$	$<8\text{ mg/L}$	$82.2\%$ Total N	Heterotrophic bacterial denitrification
MBR Aerobic Tank	Anoxic Effluent	$\text{BOD}_5$ , COD, $NH_3-N$	$1,650\text{ mg/L BOD}$	$<10\text{ mg/L BOD}$	$99.4\%$ BOD, $93.0\%$ COD	Aerobic oxidation & Nitrification
Submerged UF MBR	Aeration Mixed Liquor	MLSS Solids, Bacteria	$9,000\text{ mg/L}$	$<1\text{ mg/L TSS}$	$>99.99\%$ TSS (SDI $< 1.8$ )	$0.04\ \mu\text{m}$ PVDF membrane barrier
High Recovery RO	Combined MBR + Stream C	Dissolved Salts (TDS), COD	$2,190\text{ mg/L}$	$<45\text{ mg/L TDS}$	$98.5\%$ TDS Rejection ( $85\%$ Water Recovery)	Polyamide TFC Osmotic Separation
MVRE Evaporator	Stream A + RO Reject	High TDS Brine, COD	$39,248\text{ mg/L}$	$<25\text{ mg/L TDS}$	$>99.9\%$ TDS Rejection ( $88.8\%$ Water Recovery)	Mechanical vapor recompression thermal boiling
ATFD Crystallizer	MVRE Slurry ( $35\%$ TDS)	Concentrated Salt	$350,000\text{ mg/L}$	$10\%$ moisture salt	$100\%$ Salt Recovery	Thin film thermal contact drying

# 3. Exhaustive Tank & Vessel Sizing Table ( $250\text{ m}^3/\text{day}$ Plant Capacity)

Below is the complete engineering sizing table for all civil and mechanical vessels in the $500\text{ KL}$ reactor volume API complex:

Tank / Unit Name	HRT / SRT	Flow ( $m^3/\text{hr}$ )	Active Vol ( $m^3$ )	Dimensions ( $L \times W \times \text{Liquid Depth}$ )	Total Depth (m)	Total Vol ( $m^3$ )	MOC	Internal Agitation / Equipment
1. Raw Collection Pit	$2.0\text{ hrs}$	$10.42$	$20.8$	$3.0\text{ m} \times 2.5\text{ m} \times 2.8\text{ m}$	$3.3\text{ m}$	$24.75$	RCC M30 + FRP	Coarse manual bar screen
2. CPI Oil Separator	$1.0\text{ hr}$	$5.83$	$5.83$	$2.5\text{ m} \times 1.2\text{ m} \times 2.0\text{ m}$	$2.4\text{ m}$	$7.20$	RCC + FRP	Oleophilic TPI plate pack
3. LTDS Equalization	$24.0\text{ hrs}$	$5.83$	$140.0$	$7.0\text{ m} \times 5.0\text{ m} \times 4.0\text{ m}$	$4.5\text{ m}$	$157.50$	RCC + FRP	Air grid ( $168\text{ m}^3/\text{hr}$ ) + Air Blowers
4. Neutralization Tank	$0.25\text{ hr}$	$5.83$	$1.46$	$1.2\text{ m} \times 1.2\text{ m} \times 1.1\text{ m}$	$1.5\text{ m}$	$2.16$	RCC + FRP	High-speed agitator ( $1.5\text{ kW}$ )
5. Flash Mixer / Floc	$0.25\text{ hr}$	$5.83$	$1.46$	$1.2\text{ m} \times 1.2\text{ m} \times 1.1\text{ m}$	$1.5\text{ m}$	$2.16$	RCC + FRP	Slow paddle flocculator ( $0.75\text{ kW}$ )
6. Primary DAF Basin	$0.50\text{ hr}$	$5.83$	$2.91$	$2.0\text{ m} \times 1.2\text{ m} \times 1.25\text{ m}$	$1.65\text{ m}$	$3.96$	SS304	Air saturation vessel + scraper
7. Anoxic Tank	$4.0\text{ hrs}$	$5.83$	$23.33$	$3.0\text{ m} \times 2.5\text{ m} \times 3.2\text{ m}$	$3.7\text{ m}$	$27.75$	RCC + Epoxy	Submersible mixer ( $1.5\text{ kW}$ )
8. MBR Aeration Tank	$44.6\text{ hrs}$	$5.83$	$260.0$	$10.0\text{ m} \times 6.5\text{ m} \times 4.0\text{ m}$	$4.5\text{ m}$	$292.50$	RCC + Epoxy	Fine bubble grid ( $506\text{ m}^3/\text{hr}$ )
9. MBR Membrane Tank	$1.0\text{ hr}$	$7.00$	$7.00$	$2.5\text{ m} \times 1.4\text{ m} \times 2.0\text{ m}$	$2.5\text{ m}$	$8.75$	SS316L	Submerged UF cassettes + air scour
10. MBR Permeate Sump	$4.0\text{ hrs}$	$5.83$	$23.33$	$3.0\text{ m} \times 2.5\text{ m} \times 3.2\text{ m}$	$3.7\text{ m}$	$27.75$	RCC + Epoxy	Level switches + Transfer pumps
11. Combined RO Feed	$2.0\text{ hrs}$	$8.96$	$17.92$	$3.0\text{ m} \times 2.0\text{ m} \times 3.0\text{ m}$	$3.5\text{ m}$	$21.00$	RCC + Epoxy	Cartridge filters ( $5\ \mu\text{m}$ )
12. RO Permeate Tank	$12.0\text{ hrs}$	$7.61$	$91.32$	$6.0\text{ m} \times 5.0\text{ m} \times 3.1\text{ m}$	$3.6\text{ m}$	$108.00$	RCC + Epoxy	Plant supply pumps ( $2\times 5.5\text{ kW}$ )
13. HTDS Equalization	$24.0\text{ hrs}$	$1.46$	$35.00$	$4.0\text{ m} \times 3.0\text{ m} \times 3.0\text{ m}$	$3.5\text{ m}$	$42.00$	RCC + FRP	Mechanical agitator ( $2.2\text{ kW}$ )
14. MVRE Feed Tank	$24.0\text{ hrs}$	$2.80$	$67.25$	$5.0\text{ m} \times 4.5\text{ m} \times 3.0\text{ m}$	$3.5\text{ m}$	$78.75$	RCC + FRP	Anti-scalant & pH dosing
15. MVRE Condensate	$12.0\text{ hrs}$	$2.49$	$29.88$	$3.5\text{ m} \times 3.0\text{ m} \times 2.9\text{ m}$	$3.4\text{ m}$	$35.70$	RCC + Epoxy	Reuse transfer pumps ( $2\times 3.7\text{ kW}$ )
16. WAS Sludge Tank	$48.0\text{ hrs}$	$0.50$	$24.00$	$3.0\text{ m} \times 2.5\text{ m} \times 3.2\text{ m}$	$3.7\text{ m}$	$27.75$	RCC + Epoxy	Air agitation grid ( $35\text{ m}^3/\text{hr}$ )

# 4. Plant Utility & Electrical Connected Load Summary

An audit-ready DBR must quantify all electrical drives, steam consumption, compressed air, and chemical dosing requirements.

# 4.1 Electrical Power Consumption Summary

Major Equipment / Drive	Quantity (Duty + Standby)	Installed Rating (kW each)	Operating Load (kW)	Daily Power (kWh/day)
Raw Effluent Lift Pumps	$1\text{W} + 1\text{S}$	$3.70\text{ kW}$	$3.20\text{ kW}$	$76.8\text{ kWh}$
LTDS Equalization Air Blowers	$1\text{W} + 1\text{S}$	$7.50\text{ kW}$	$6.10\text{ kW}$	$146.4\text{ kWh}$
Neutralization & Flash Agitators	$2\text{W} + 0\text{S}$	$2.25\text{ kW}$	$1.80\text{ kW}$	$43.2\text{ kWh}$
DAF Recycle Pump & Compressor	$1\text{W} + 1\text{S}$	$5.50\text{ kW}$	$4.40\text{ kW}$	$105.6\text{ kWh}$
Anoxic Submerged Mixer	$1\text{W} + 0\text{S}$	$1.50\text{ kW}$	$1.20\text{ kW}$	$28.8\text{ kWh}$
Internal Nitrate Recycle Pump	$1\text{W} + 1\text{S}$	$3.00\text{ kW}$	$2.40\text{ kW}$	$57.6\text{ kWh}$
MBR Aeration Main Air Blowers	$1\text{W} + 1\text{S}$	$18.50\text{ kW}$	$15.20\text{ kW}$	$364.8\text{ kWh}$
MBR Air Scouring Blower	$1\text{W} + 1\text{S}$	$11.00\text{ kW}$	$9.00\text{ kW}$	$180.0\text{ kWh}$ (Cyclic)
MBR Suction Permeate Pumps	$1\text{W} + 1\text{S}$	$4.00\text{ kW}$	$3.30\text{ kW}$	$79.2\text{ kWh}$
RO High Pressure Feed Pumps	$1\text{W} + 1\text{S}$	$18.50\text{ kW}$	$15.80\text{ kW}$	$379.2\text{ kWh}$
MVRE Vapor Compressor Blower	$1\text{W} + 0\text{S}$	$45.00\text{ kW}$	$38.50\text{ kW}$	$924.0\text{ kWh}$
MVRE Forced Circulation Pump	$1\text{W} + 1\text{S}$	$22.00\text{ kW}$	$18.00\text{ kW}$	$432.0\text{ kWh}$
ATFD Drive Motor & Vacuum	$1\text{W} + 0\text{S}$	$7.50\text{ kW}$	$6.00\text{ kW}$	$144.0\text{ kWh}$
Screw Press Sludge Dewatering	$1\text{W} + 0\text{S}$	$3.70\text{ kW}$	$2.80\text{ kW}$	$22.4\text{ kWh}$ ( $8\text{ hr/day}$ )
Chemical Dosing Pumps (6 Sets)	$6\text{W} + 6\text{S}$	$2.22\text{ kW}$ (Total)	$1.50\text{ kW}$	$36.0\text{ kWh}$
TOTAL ETP/ZLD POWER LOAD	--	$156.87\text{ kW}$	$130.60\text{ kW}$	$3,137.2\text{ kWh/day}$

\text{Specific Electrical Energy Consumption} = \frac{3,137.2\text{ kWh/day}}{250\text{ m}^3/\text{day}} = \mathbf{12.55\text{ kWh / m}^3 \text{ raw effluent treated}}

# 4.2 Thermal Steam & Chemical Consumption Summary

  UTILITY & CHEMICAL CONSUMPTION BREAKDOWN (Per Day Basis)
  ┌─────────────────────────┬──────────────────────────┬────────────────────────────────────────┐
  │ Utility / Chemical      │ Daily Requirement        │ Primary Application Point              │
  ├─────────────────────────┼──────────────────────────┼────────────────────────────────────────┤
  │ Low Pressure Steam      │ 320 kg/hr (7.68 MT/day)  │ ATFD Dryer & MVRE Startup Heating      │
  │ Compressed Utility Air   │ 45 CFM at 6.0 bar        │ Valve Actuators & Instrument Air       │
  │ Sulfuric Acid (98% H2SO4)│ 45.0 kg/day              │ Neutralization Tank pH adjustment      │
  │ Caustic Lye (30% NaOH)  │ 35.0 kg/day              │ Neutralization & RO CIP Cleaning       │
  │ PAC / Alum Coagulant    │ 25.0 kg/day              │ Primary DAF Flocculation               │
  │ Polyelectrolyte Polymer │ 2.5 kg/day               │ DAF Flotation & Screw Press Dewatering │
  │ RO Phosphonate Antiscalant│ 3.5 kg/day             │ Combined RO Feed Dosing Line           │
  │ Defoamer / Anti-foam    │ 5.0 kg/day               │ MBR Aeration Tank Foam Control         │
  └─────────────────────────┴──────────────────────────┴────────────────────────────────────────┘

# 5. Detailed High-Recovery Reverse Osmosis (RO) Sizing in LTDS

Reverse Osmosis is the primary water recovery workhorse for Low TDS (LTDS) effluents.

# 5.1 Pre-treatment Requirements & Feed Water Quality

Before feeding MBR permeate to RO membranes, enforce strict limits to prevent biofouling, organic fouling, and scaling:

Silt Density Index ( $ext{SDI}_{15}$ ): $< 2.0$ (Guaranteed by $0.04\ \mu\text{m}$ MBR UF membrane).
Total Suspended Solids (TSS): $< 1.0\text{ mg/L}$ .
Turbidity: $< 0.2\text{ NTU}$ .
Free Chlorine: $< 0.05\text{ mg/L}$ (Prevents polyamide membrane oxidation).
Oil & Grease: $< 0.5\text{ mg/L}$ .

# 5.2 RO Array Configuration & Sizing Equations

Combined RO Feed Flow ( $Q_f$ ): MBR Permeate ( $140\text{ m}^3/\text{day}$ ) + Utility Stream C ( $75\text{ m}^3/\text{day}$ ) = $215\text{ m}^3/\text{day}$ ( $8.96\text{ m}^3/\text{hr}$ ).
Design Water Recovery ( $Y$ ): $85.0\%$ .

Q_p = Q_f \times Y = 215 \times 0.85 = \mathbf{182.75\text{ m}^3/\text{day} \ (7.61\text{ m}^3/\text{hr})}

Q_r = Q_f \times (1 - Y) = 215 \times 0.15 = \mathbf{32.25\text{ m}^3/\text{day} \ (1.34\text{ m}^3/\text{hr})}

RO Membrane Array: 2-Stage System with a 2:1 Pressure Vessel Array Ratio (4 Vessels in Stage 1, 2 Vessels in Stage 2, each vessel containing 6 Spiral Wound 8040 Polyamide TFC Elements $= 36$ total elements).
Total Active Membrane Area ( $A_m$ ): $36\text{ elements} \times 37.2\text{ m}^2/\text{element} = 1,339.2\text{ m}^2$ .
Average Design Flux ( $J$ ):

J = \frac{7.61\text{ m}^3/\text{hr} \times 1,000\text{ L/m}^3}{1,339.2\text{ m}^2} = \mathbf{5.68\text{ LMH}} \quad (\text{Highly conservative, anti-fouling flux})

Operating Pressures:
- Stage 1 Feed Pressure: $13.5\text{ bar(g)}$ .
- Interstage Booster Pump: Adds $4.5\text{ bar}$ $\Rightarrow$ Stage 2 Feed Pressure $= 17.0\text{ bar(g)}$ to overcome osmotic pressure ( $12.8\text{ bar}$ ).
Permeate & Reject Quality:
- RO Permeate TDS: $2,190\text{ mg/L} \times (1 - 0.985) = \mathbf{32.8\text{ mg/L}}$ (Recycled to Cooling Towers).
- RO Reject TDS:

\text{TDS}_{\text{reject}} = \frac{\text{TDS}_{\text{feed}} - (Y \times \text{TDS}_{\text{permeate}})}{1 - Y} = \frac{2,190.7 - (0.85 \times 32.8)}{0.15} = \mathbf{14,419\text{ mg/L}}

# 6. Mechanical Vapor Recompression Evaporator (MVRE) Sizing for RO Reject & HTDS Water

Mechanical Vapor Recompression (MVRE) is a revolutionary energy-saving evaporator technology ideal for concentrating RO reject water ( $32.25\text{ m}^3/\text{day}$ ) combined with High TDS Mother Liquors ( $35.0\text{ m}^3/\text{day}$ ).

# 6.1 MVRE vs. Conventional Multiple Effect Evaporator (MEE) Comparison

  CONVENTIONAL TRIPLE EFFECT MEE vs. MECHANICAL VAPOR RECOMPRESSION (MVRE)
  
  Triple Effect MEE (Requires Live Steam Boiler):
  [Boiler Steam 1000 kg/h] ──► [Effect 1] ──► [Effect 2] ──► [Effect 3] ──► [Condenser / Cooling Tower]
  * Steam Economy: 2.8 kg water / kg steam (High thermal energy cost)
  
  Mechanical Vapor Recompression (MVRE - Power Driven):
  ┌────────────────────────────────────────────────────────────────────────┐
  │                                                                        │
  ▼                                                                        │
[Evaporator Vessel] ──(Vapor 100°C)──► [Vapor Compressor Motor 45 kW] ──(Vapor 106.5°C)
  ▲                                           │ (Compressed Vapor as Heating Steam)
  └───────────────────(Heat Transfer)─────────┘
  * Equivalent Steam Economy: 18 - 25 kg water / kg steam equivalent (75% OPEX Reduction!)

# 6.2 MVRE Thermal & Mechanical Sizing Calculations

Combined MVRE Feed Rate ( $Q_{\text{MVRE}}$ ): High COD Stream A ( $35.0\text{ m}^3/\text{day}$ ) + RO Reject ( $32.25\text{ m}^3/\text{day}$ ) = $67.25\text{ m}^3/\text{day}$ ( $2.80\text{ m}^3/\text{hr}$ ).
Feed TDS: $39,248\text{ mg/L} \approx 3.92\% \text{ (w/w)}$ .
Target Concentrated Slurry TDS: $35.0\% \text{ (w/w)}$ .
Water Evaporation Rate ( $W_v$ ):

W_v = 67.25\text{ m}^3/\text{day} \times \left( 1 - \frac{3.92}{35.0} \right) = \mathbf{59.72\text{ m}^3/\text{day} \ (2.49\text{ m}^3/\text{hr} = 2,488\text{ kg/hr})}

MVRE Distillate Condensate Recovery: $59.72\text{ m}^3/\text{day}$ ( $\text{TDS} < 20\text{ mg/L}$ , $\text{COD} < 35\text{ mg/L}$ ). Recycled for plant washing.
Concentrated Slurry Flow to ATFD: $67.25 - 59.72 = \mathbf{7.53\text{ m}^3/\text{day} \ (314\text{ L/hr})}$ .
Vapor Compressor Motor Power Calculation:
- Vapor flow rate: $2,488\text{ kg/hr} = 0.691\text{ kg/s}$ .
- Suction temperature: $100.0^\circ\text{C}$ ( $1.013\text{ bar(a)}$ ).
- Compressor pressure ratio: $p_2/p_1 = 1.28$ ( $Delta T_{\text{sat}} = 6.5^\circ\text{C}$ temperature boost to $106.5^\circ\text{C}$ ).
- Isentropic compressor shaft power:

P_{\text{comp}} = \frac{\dot{m} \cdot C_p \cdot T_1}{\eta_{\text{comp}}} \left[ \left( \frac{p_2}{p_1} \right)^{\frac{\gamma-1}{\gamma}} - 1 \right] = \frac{0.691 \times 2.01 \times 373.15}{0.75} \left[ (1.28)^{0.23} - 1 \right] = \mathbf{38.5\text{ kW}}

*   Adopt ** $45.0\text{ kW}$  Heavy-Duty Centrifugal Vapor Fan/Compressor Drive**.

MVRE Specific Energy Consumption:

\text{Specific Power} = \frac{38.5\text{ kW}}{2.49\text{ m}^3/\text{hr}} = \mathbf{15.46\text{ kWh / m}^3 \text{ water evaporated}}

Evaporator Heat Transfer Area (HTA):
- Latent heat of condensation $\lambda = 2,240\text{ kJ/kg}$ .
- Heat Duty $Q_{\text{thermal}} = 2,488\text{ kg/hr} \times 2,240\text{ kJ/kg} \div 3,600 = 1,548\text{ kW}$ .
- Overall Heat Transfer Coefficient $U = 2,200\text{ W/m}^2\cdot K$ (Falling Film Titanium tubes).
- Temperature difference $\Delta T = 6.5 - 1.8\text{ (Boiling Point Elevation BPE)} = 4.7^\circ\text{C}$ .
- Required HTA:

A_{\text{HTA}} = \frac{Q_{\text{thermal}}}{U \times \Delta T} = \frac{1,548,000}{2,200 \times 4.7} = \mathbf{149.7\text{ m}^2} \quad (\text{Adopt Titanium Gr. 2 Tubes})

# 7. Statutory CPCB Discharge Standards vs. ZLD Reuse Specifications

The DBR must contrast environmental discharge standards against internal factory ZLD water reuse quality targets:

Water Quality Parameter	CPCB Inland Surface Water Discharge Limits	CPCB On-Land Irrigation Norms	ZLD Cooling Tower Makeup Target	ZLD High Pressure Boiler Feed Target
pH	$6.5 - 8.5$	$5.5 - 9.0$	$7.0 - 8.2$	$8.5 - 9.5$
Total Suspended Solids (TSS)	$< 100\text{ mg/L}$	$< 200\text{ mg/L}$	$< 5.0\text{ mg/L}$	$< 0.1\text{ mg/L}$
BOD $_5$ (at 20°C)	$< 30\text{ mg/L}$	$< 100\text{ mg/L}$	$< 5.0\text{ mg/L}$	$0.0\text{ mg/L}$
Chemical Oxygen Demand (COD)	$< 250\text{ mg/L}$	No standard	$< 30\text{ mg/L}$	$< 2.0\text{ mg/L}$
Total Dissolved Solids (TDS)	$< 2,100\text{ mg/L}$	$< 2,100\text{ mg/L}$	$< 150\text{ mg/L}$ (RO Permeate)	$< 0.5\text{ mg/L}$ (Post DM)
Oil & Grease (O&G)	$< 10\text{ mg/L}$	$< 10\text{ mg/L}$	$< 1.0\text{ mg/L}$	$0.0\text{ mg/L}$
Ammoniacal Nitrogen ( $NH_3-N$ )	$< 50\text{ mg/L}$	No standard	$< 2.0\text{ mg/L}$	$< 0.1\text{ mg/L}$
Silt Density Index ( $ext{SDI}_{15}$ )	Not applicable	Not applicable	$< 3.0$	$< 1.0$
Bio-assay (Fish Survival)	$90\%$ survival in 96 hrs	$90\%$ survival	Not applicable	Not applicable

# 8. Standard Design Basis Report (DBR) Document Template & Checklist

When submitting a DBR for engineering execution or regulatory approval, format the document into 8 standard sections:

# DESIGN BASIS REPORT (DBR)
## LOW TDS BIOLOGICAL ETP, MVRE & ZERO LIQUID DISCHARGE (ZLD) PLANT
### Project: [Plant Name / 500 KL API Manufacturing Unit]

1. INTRODUCTION & PROJECT OVERVIEW
   1.1 Facility Background & Manufacturing Campaigns
   1.2 Statutory Regulatory Framework (CPCB/SPCB Consent Standards)
   1.3 Battery Limits & Scope of Supply

2. EFFLUENT GENERATION & STREAM SEGREGATION
   2.1 Mass Balance of Process Washes, MLs & Utility Blowdowns
   2.2 Stream Classification Matrix (Stream A - HTDS, Stream B - LTDS, Stream C, Stream D)
   2.3 Effluent Characterization Table (Avg, Max, Design Basis)

3. PROCESS FLOWSHEET ARCHITECTURE & UNIT SELECTION
   3.1 HTDS Solvent Stripper Column & MVRE/ATFD System
   3.2 LTDS Equalization & Primary CPI/DAF Unit
   3.3 LTDS Anoxic Denitrification & Membrane Bioreactor (MBR) System
   3.4 Combined Tertiary High Recovery Reverse Osmosis (RO)

4. DETAILED ENGINEERING SIZING CALCULATIONS
   4.1 Tank Volumes, HRT, and Mixing Power
   4.2 Biological Aeration Kinetics (F/M, MLSS, AOR/SOR, Blower CFM, Membrane LMH)
   4.3 RO Membrane Flux, Osmotic Pressure & Recovery Percentages
   4.4 MVRE Vapor Compressor Power, HTA, and Specific Energy Consumption

5. OVERALL WATER & MASS BALANCE
   5.1 Daily Water Balance Block Flow Diagram (BFD)
   5.2 Solid Waste Generation (Biological Sludge, Primary Sludge, MEE Salt)

6. MATERIALS OF CONSTRUCTION (MOC) MATRIX
   6.1 Tanks & Civil Structures (RCC with FRP/Epoxy Lining)
   6.2 Pumps, Piping & Valves (SS316L, Duplex 2205, PP, HDPE)
   6.3 Heat Exchanger Tubes (Titanium Gr. 2 / Duplex 2205 for MVRE)

7. UTILITY & ELECTRICAL CONNECTED LOAD
   7.1 Power Consumption Summary (KW installed / operating)
   7.2 Steam Consumption (kg/hr at pressure bar)
   7.3 Chemical Dosing Requirements (Caustic, Acid, Coagulant, Anti-scalant)

8. INSTRUMENTATION, CONTROL & ONLINE CPCB TRANSMISSION
   8.1 PLC / SCADA Automation Level
   8.2 Online Effluent Monitoring System (pH, TOC, COD, BOD, Flowmeters)

# 9. Summary Checklist for DBR Approval

Before freezing the ETP/ZLD Design Basis Report for procurement, verify:

LTDS ( $ext{TDS} < 3,500 ext{ mg/L}$ ) and HTDS ( $ext{TDS} > 15,000 ext{ mg/L}$ ) streams strictly segregated at source.
Peak hourly factor ( $1.5 - 2.0$ ) applied to hydraulic pump sizing.
Biological F/M ratio kept between $0.08 - 0.15$ for stable MBR performance.
Aeration blowers sized with altitude and ambient temperature correction factors.
RO recovery rate ( $85%$ ) validated against membrane projection software.
MVRE vapor compressor power ( $38.5 ext{ kW}$ ) and Titanium HTA ( $150 ext{ m}^2$ ) verified for chloride corrosion.
Complete plant water balance closes with $<3\%$ mass discrepancy.
Online CPCB/SPCB data transmission telemetry interfaces included.

# 10. Regulatory Standards & Engineering References

CPCB India: Charter for Water Recycling and Pollution Control in Bulk Drug Industries.
US-EPA: 40 CFR Part 439 - Pharmaceutical Manufacturing Point Source Category.
Metcalf & Eddy: Wastewater Engineering: Treatment and Resource Recovery (5th Edition).
ISO 14001:2015: Environmental Management Systems — Requirements with Guidance for Use.