TANNERY WASTE WATER TREATMENT FLOW CHART WITH ZLD

Source of the article: http://www.slideserve.com/camden/introduction-to-t-he-t-reatment-of-tannery-effluents/?utm_source=slideserve&utm_medium=website&utm_campaign=auto+related+load

Design of DAF with calculation for 1000 KLD ETP

Design of  DAF with  calculation for 1000 KLD  ETP

Indian Norms

India follows effluent discharge standards under the Environment (Protection) Act, 1986 and CPCB/SPCB consents. Typical limits for  discharge are:

pH: 6.5–8.5

BOD ≤ 30 mg/L

COD ≤ 250 mg/L

Suspended Solids ≤ 50 mg/L

Oil & Grease ≤ 10 mg/L 

DAF should be designed to remove TSS, oil/grease and floatables to protect downstream biological and tertiary units.

2. Flow & Basic Parameters

Design flow: 1000 m³/day

→ Convert to m³/hr:

1000 m³/day ÷ 24 ≈ 41.7 m³/hr

For design, include recycle for air saturation of ~20% of flow.

→ Recycle = 0.20 × 41.7 ≈ 8.3 m³/hr

→ Total hydraulic load entering DAF = ~50 m³/hr

3. DAF Hydraulic Sizing

3.1 Surface Loading Rate

Standard design uses a surface loading rate ~4–6 m³/m²·hr for industrial wastewater DAF. 

Take 5 m³/m²·hr as a reasonable design value.

So required effective surface area:

Surface Area = Flow / Loading rate

= 50 m³/hr ÷ 5 m³/m²·hr

= 10 m²

3.2 Dimensions

Use a rectangular DAF tank with length-to-width ratio ~3:1 (common in wastewater DAF design).

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From Surface Area = L × W = 10 m²

Assume L = 3×W

=> 3W² = 10 → W² = 3.33 → W ≈ 1.82 m

→ L ≈ 5.46 m

3.3 Depth

Effective water depth in DAFs is typically 1.2–1.5 m. 

Use 1.5 m for adequate retention and floc contact.

Tank volume ≈ 5.46 × 1.82 × 1.5 ≈ 14.9 m³

4. Check for Hydraulic Retention Time (HRT)

HRT in DAF separation zone is usually around 15–30 min.

Check: 14.9 m³ / 50 m³/hr = 0.298 hr ≈ 17.9 min — falls within design range.

5. Air Saturation & Recycle System

Pressurization

Recycle pressurized to ~4–6 bar (60–90 psi) typical for microbubble generation.

Recycle Pump

Recycle pump sized ~8.3 m³/hr at pressure ~6 bar.

Motor ~2.2 kW (~3 HP), considering friction losses.

Air Compressor

Air requirement depends on solids load and design conditions; typical air to solids ratio ~0.02–0.06 lb air/lb solids. 

For initial costing assume 1 HP air compressor (~0.75 kW) capable of delivering required compressed air.

6. Skimming & Sludge Handling

Surface skimmer with conveyor sized to span full width.

Sludge hopper below flotation zone.

Provision for pneumatic or geared scraper.

7. Chemical Pretreatment

DAF in  ETP usually works with coagulation/flocculation upstream (rapid mix and flocculation tanks) to aggregate fine particles and improve bubble attachment.

8. Material & Construction

Main tank and attachments:

Stainless Steel SS304 (tank, skimmer, piping) — suitable for corrosive wastewater and cleaning regimes.

Other materials:

Flocculation tank can be concrete or SS304 if space limited.

Pump base SS304 with mechanical seals.

Pressure vessels rated to ASME standards.

9. Equipment Selection & HP Summary

Motor / HP (Approx)

Equipment

Qty

Notes

Recycle pump

1

3–5 HP

High pressure pump

Air compressor

1

1–2 HP

Pressure to 4–6 bar

Skimmer drive

1

0.5–1 HP

Slow-speed scraper

Chemical dosing pumps

2

0.5 HP each

Coagulant & polymer

Total electrical ~7–9 HP (~5–7 kW) installed.

10. Estimated Costs in India (Indicative)

All pricing is approximate, based on recent Indian market supply ranges for industrial DAF systems and SS304 fabrication — these are typical ballpark figures.

Item

Approx Price (₹)

SS304 DAF Tank & Skimmer + fabrication

6,00,000 – 8,50,000

High-pressure recycle pump + driver

80,000 – 1,20,000

Air compressor (1–2 HP)

70,000 – 1,00,000

PLC + instrumentation + valves

1,00,000 – 1,50,000

Chemical dosing skid

50,000 – 70,000

Piping & installation

1,00,000 – 1,50,000

Civil foundation & site work

1,50,000 – 2,00,000

Estimated total: ₹12 – 16 lakhs approx (for the DAF unit including ancillary equipment, excluding civil structure alterations and commissioning consumables).

Prices vary by  fabrication, location, and detailed design for various types of inlet waste water parameters.

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