Slaughter house ETP Design 500 KLD Capacity By CHATGPT
Notes on Standards
Use PHEED for Indian empirical correction factors and safety factors.
Metcalf & Eddy for biological kinetics (k, Ks), aeration and secondary treatment design.
Adjust detention times and loads with lab analysis and local conditions.
ANSWER By CHATGPT
Assumptions (used everywhere)
Plant flow (average): Q = 500 m³/day = 20.833 m³/hr (continuous).
Representative influent (from your earlier inputs / typical slaughterhouse): COD 5,000 mg/L, BOD₅ = 2,000 mg/L, TSS = 2,000 mg/L, FOG = 1,000 mg/L.
Anaerobic (UASB) COD removal: 65% (design basis). Result used downstream.
Design safety / sizing factors: apply 20–30% spare capacity or safety factor on hydraulic areas/ membrane areas and 30% on membrane area unless noted. Where design ranges exist I choose conservative mid/high values for reliability. Design references are shown inline.
1) Coarse screening
Purpose: remove rags, large bones, plastics; protect downstream pumps/ drum screen.
Design:
Bar spacing: 10 mm (coarse) for slaughterhouse (use a finer 6 mm if many small solids).
Peak/continuous flow: 21 m³/hr → choose screening capacity for 30 m³/hr to allow surges.
Typical item: coarse channel screen or perforated step screen. Provide a wash/compactor or manual basket.
Headloss: design ~10–50 mm. Provide trash bin sized for daily accumulation (estimate ~10–20 kg/day coarse solids; depends on operations).
Recommendation: stainless steel (SS304/316) with a bypass manual screen and access for cleaning.
2) Oil trap / grease interceptor (before equalization)
Purpose: remove free-floating oils/grease to reduce downstream fouling.
Design basis & calculation:
Use 2 hours hydraulic detention (typical interceptor detention 30 min–2 hr for food industry grease traps; choose 2 hr to be conservative).
Volume = Q_hr × detention = 20.833 m³/hr × 2 hr = 41.7 m³.
Use two compartments (inlet baffle + separation zone + cleanout sump). Depth ~1.2–1.8 m. For compact footprint pick 1.5 m depth → plan area = 41.7 / 1.5 = 27.8 m² → e.g., 7 m × 4 m footprint.
Notes: provide skimming port, access manholes, sludge/grease collection tray. Material: GRP or SS depending on budget.
3) Equalization tank (with drum solid separator)
Purpose: dampen flow/load variations; allow coarse solids separation (drum screen) and chemical dosing if needed.
Design assumptions:
For high-strength slaughterhouse waste, recommended EQ storage = 1–1.5 days to homogenize and give time for downstream chemical dosing/pH adjustments. I’ll size 1.5 days as in earlier plan.
Calculation:
Volume = Q × 1.5 day = 500 m³/day × 1.5 = 750 m³.
Provide mixing (slow mixers) to avoid short-circuiting; mechanical mixers or coarse bubble aeration to prevent septic conditions. If anaerobic pre-treatment is used immediately after EQ, DO control may be needed.
Drum screen: install as bypass/inline solids removal inside EQ: design for continuous throughput ~21 m³/hr. Typical drum screen flux (vendor dependent) handles dozens to hundreds m³/hr per unit; specify vendor model for Q=25 m³/hr with 1–2 mm perforations. Provide rakes, wash water and 1.5–2 hour solids hopper.
Recommendation: EQ as rectangular concrete tank in 2 compartments (settling & buffer) with level control for equalization and automatic dosing skid for coagulant / pH if needed.
4) DAF (FOG recovery)
Purpose: remove dissolved/ emulsified oils & greases, remaining floatables; concentrate FOG for rendering or digestion.
Design criteria (industry ranges):
Hydraulic Loading Rate (HLR) for DAF in meat processing: typically 5–10 m³/m²·hr (high-rate DAF); many vendors design 4–10 m³/m²·hr. I choose 6 m³/m²·hr (conservative, compact).
Calculation:
Hourly flow Qh = 20.833 m³/hr.
Required DAF area A = Qh / HLR = 20.833 / 6 = 3.472 m². Apply practical plate-pack geometry (effective area multiplies by plate factor 3–6). Choose a plate-pack DAF with plate pack factor 5 → actual tank footprint ≈ 3.472 / 5 = 0.695 m² (very compact) — vendors typically give modular units; choose a standard DAF rated for 25 m³/hr.
Typical recycle (saturation) ratio 10–20% → design recirc pump capacity ~ 5 m³/hr and air saturator at 4–6 barg. Sludge (float) concentration: 3–6% solids; expected daily DAF float ~ 200–350 kg dry solids (depends on FOG/TSS removal %).
Notes: include polymer/coagulant dosing skid upstream, skimmer and float hopper with pump to sludge tank. Material: SS316 recommended.
5) Primary clarifier (after DAF)
Purpose: remove remaining settleable solids before biological treatment.
Design criteria:
Surface overflow rate (SOR) for primary clarifiers (industrial): 25–40 m³/m²·day average. I’ll use 30 m³/m²·day (conservative).
Calculation:
Flow Q = 500 m³/day.
Area A = Q / SOR = 500 / 30 = 16.67 m². Add 30% safety factor → ~21.7 m². Choose a circular clarifier: area πD²/4 = 21.7 → D = sqrt(4×21.7/π) = ≈5.26 m → choose 6 m diameter clarifier.
Depth: 3.0–3.5 m. Volume ≈ area × depth ≈ 21.7 × 3.5 ≈ 76 m³. Provide sludge hopper and scum removal.
Notes: Provide inlet baffle, flow-distribution box, sludge withdrawal pump to sludge handling.
6) Anaerobic reactor — UASB
Purpose: remove bulk COD, generate biogas for energy recovery.
Design basis used earlier (restated with steps):
COD influent = 2,500 kg/day (500 m³ × 5,000 mg/L). Design OLR = 4 kg COD/m³·day (conservative/mid-range for UASB on high-strength wastes).
Calculation:
Required UASB volume = COD load / OLR = 2,500 / 4 = 625 m³.
HRT = Volume / Q = 625 / 500 = 1.25 day = 30 hours. (UASB HRTs typically 12–48 hr for strong wastes; 30 h is conservative.)
COD removal expected ≈ 60–70% → design 65% (1,625 kg/day removed). Remainder COD to aerobic stage ≈ 875 kg/day → concentration post-UASB ~1,750 mg/L COD.
Gas handling: CH₄ ≈ 0.35 m³ CH₄/kg COD removed → CH₄ ≈ 569 m³/day. Provide gas holder, condensate trap, H₂S mitigation (if H₂S high), flare/CHP skid.
Reactor geometry & internals: typical UASB height 4–6 m; provide gas–solid–liquid separator (GSL), influent distribution, sludge withdrawal. Material: concrete with internal lining or FRP/steel if modular.
7) Aerobic treatment — Aeration tank 1 → Clarifier 1 → Aeration tank 2 → Clarifier 2 → Disinfection
You specified two-stage aerobic with two clarifiers. I size the total aerobic system to reach polishing BOD ≈ <30 mg/L (ready for filtration + RO).
Design approach: compute required aerobic volume from remaining BOD load after UASB and volumetric loading (kg BOD/m³·day).
Step A — Estimate BOD load to aerobic:
Influent BOD load = 500 × 2,000 mg/L = 1,000 kg BOD/day.
Assume UASB removes 60% BOD (approx. aligned with COD removal), so BOD to aerobic = 1,000 × (1 − 0.60) = 400 kg/day. (This matches earlier quick calc.)
Step B — Aerobic volumetric loading (typical):
For high-strength industrial effluent use volumetric organic loading (VLR) = 1.5 kg BOD/m³·day (conservative high-rate design). Range 0.5–3 kg/m³·day used in literature; 1.5 is reasonable for reliable removal.
Calculation:
Aeration basin total volume V = BOD to treat / VLR = 400 / 1.5 = 266.7 m³.
Split into two identical aeration tanks: V1 = V2 = 133.3 m³.
HRT total = V / Q = 266.7 / 500 = 0.533 day = 12.8 hr → per tank ≈ 6.4 hr HRT each (reasonable for high-rate activated sludge).
MLSS / SRT (guidance):
Choose MLSS near 3,500–4,500 mg/L for strong industrial BOD; pick 4,000 mg/L.
Calculate biomass mass: X × V = 4 kg/m³ × 266.7 m³ = 1,066.8 kg MLSS (total volatile solids basis).
Required sludge wasting (to maintain SRT) depends on chosen SRT; pick SRT = 8–12 days for conventional AS (choose 10 days). Then waste sludge VSS/day ≈ biomass / SRT = 1,066.8 / 10 = 106.7 kg VSS/day (dewater accordingly).
Aeration (O₂) requirement:
O₂ required for carbonaceous BOD removal ≈ 1.42 kg O₂ / kg BOD removed (standard). So O₂ = 400 × 1.42 = 568 kg O₂/day.
Aeration energy estimate: Standard Aeration Efficiency (SAE) for fine-bubble diffused aeration around 2.5 kg O₂/kWh (practical). Electrical energy ≈ O₂ / SAE = 568 / 2.5 = 227 kWh/day → average power ≈ 9.5 kW. (This is an indicative figure; blower and diffuser selection will refine it.)
Clarifiers (secondary) sizing:
Secondary clarifier SOR design basis: 30 m³/m²·day average (range 24–33). I’ll use 30 m³/m²·day. Include RAS flow in calculation (assume RAS = 100% of influent flow, i.e., equal to 500 m³/day). So flow to clarifier = influent (500) + RAS (500) = 1,000 m³/day.
Area per clarifier = (flow to be treated by that clarifier) / SOR. If you have two parallel trains, each clarifier handles 500 m³/day influent + 500 m³/day RAS split — practical approach: two trains each sized for 500 influent + RAS 500 → clarifier area per train = 1,000 / 30 = 33.33 m². Add 20% safety → ~40 m². Choose circular clarifier diameter: D = sqrt(4×40/π) ≈ 7.14 m → pick 7.5 m dia, depth 3.5 m.
Notes: provide scum removal, RAS pumps sized to maintain RAS rate (100% of influent) and sludge wasting pumps sized for 106.7 kg VSS/day to dewatering.
8) Disinfection tank
Purpose: final pathogen control before filtration and RO feed.
Design:
If using chlorination (or sodium hypochlorite) for non-potable reuse: typical contact time 15–30 min at designed residual; but since water later goes to RO (which will remove pathogens) you can use modest disinfection. For a conservative design use 30 min contact time.
Volume = Q_hr × contact time = 20.833 m³/hr × 0.5 hr = 10.42 m³ (for 30 min). Depth 2–3 m → area ≈ 10.42 / 2.5 = 4.17 m² (say 2 × 2.5 m tanks in series).
Notes: If using UV, design as per UV vendor (based on UVT and flow), and you can omit long contact time.
9) Pressure sand filter (PSF) → Activated carbon filter (GAC) → Coagulation + UF/MF
Purpose: final particulate removal and taste/odor/organics polishing to protect RO.
Pressure Sand Filter (rapid sand / multimedia)
Design:
Filtration rate: 5–10 m³/m²·hr for pressure sand (pick 6 m³/m²·hr conservative).
Flow for reuse water (after disinfection it's still 500 m³/day incoming, but we intend to send RO feed after coag+UF; we should size filters for RO feed flow which is the permeate target + recycle; practically RO feed = UF permeate ≈ ~400 m³/day permeate but feed to RO is 500? To be safe, filter the full plant flow or the UF feed. I’ll size filters for 500 m³/day = 20.833 m³/hr).
Area = Qh / rate = 20.833 / 6 = 3.47 m². Use two units in parallel for service/cleaning; each ~2 m² (e.g., 1.6 m dia pressure vessels).
Activated Carbon Filter (GAC)
Design:
Empty bed contact time (EBCT) typical 10–20 minutes for organics removal. Choose 15 min.
Volume = Q_hr × EBCT = 20.833 m³/hr × 0.25 hr = 5.21 m³ EBCT. Two parallel vessels, each 2.6 m³. Bed depth 0.8–1.0 m → footprint modest. Service flow velocity and contact time controlled.
Coagulation + UF/MF (pre-RO polishing)
Coagulation: Jar-tests required; typical dosing alum/Fe + polymer before UF.
UF sizing (pre-RO):
Earlier we used UF flux 50 L/m²·hr typical for industrial UF with robust membranes. That gave area ≈ 417 m²; add 20% → ~500 m². (UF flux varies widely; vendors will provide module counts.)
Practical UF layout: choose skid with multiple modules (e.g., 20–40 modules) and CIP system. UF retentate returned to sludge handling or to anaerobic digest as co-substrate (if acceptable).
10) Reverse Osmosis (RO) — staged for high recovery
Purpose: produce high-quality permeate for reuse and generate concentrate for ZLD.
Design assumptions & basis:
Target RO recovery 80% single-pass (common for industrial brackish), producing 400 m³/day permeate and 100 m³/day brine. Adjust antiscalant and pH for scaling ions.
Choose conservative RO flux 15 L/m²·hr for challenging feed (low flux prevents rapid fouling).
Permeate hourly flow = 400 m³/day ÷ 24 = 16.667 m³/hr = 16,667 L/hr.
Required membrane area = 16,667 L/hr ÷ 15 L/m²·hr = 1,111 m². Add 30% safety / spare → ~1,444 m² total membrane area. (Vendors will quote element counts; e.g., 8-inch elements ~37 m² each — you'd need ~39 elements; multiply by staging and arrays.)
RO high-pressure pump energy: typical range 3–7 kWh/m³ depending on salinity and configurations. Use 4 kWh/m³ baseline → RO electrical = 400 × 4 = 1,600 kWh/day (indicative).
Notes: include antiscalant, acid dosing, high-pressure pump with VFD, permeate polishing line, concentrate recirculation piping.
11) RO concentrate → Evaporator (or Membrane Distillation) → Crystallizer (ZLD)
Purpose: concentrate brine to solids; produce dry salts for disposal — achieve Zero Liquid Discharge.
Design approach (as before):
Brine from RO: 100 m³/day. Target final liquid <10 m³/day (overall 98% recovery). Need to evaporate 90 m³/day (convert to vapor).
Evaporator energy estimate:
Multi-effect evaporators with thermal integration typically ~100–200 kWh(th)/m³ evaporated depending on feed and number of effects. Use 150 kWh(th)/m³ for planning → thermal energy = 90 × 150 = 13,500 kWh(th)/day. (If MD chosen, low-grade heat can be used; MD energy may be less electrical but needs heat input and has scale/maintenance issues.)
Crystallizer & solids handling:
Expected solids mass: depends on salt concentration in RO brine (unknown without analysis). For conservative mass-balance: if initial dissolved solids (TDS) ~10,000–30,000 mg/L machine, solids produced could be hundreds to a few thousand kg/day. Pilot crystallizer tests will fix numbers. Provide conveyors, rotary drier or filter press to produce dry salt cake, storage shelter and transport arrangements.
Recommendation: integrate UASB biogas into a steam boiler or thermal oil loop to supply part of evaporator heat (biogas from UASB ~569 m³ CH₄/day ≈ 5,653 kWh thermal — realistically supply ~40% of evaporator heat). Evaluate fossil fuel backup and heat recovery from engines/CHP.
12) Solids offsite / disposal
DAF float: concentrated FOG and solids (3–6% solids) — send for rendering, co-digestion, or dewater and landfill as per regulations.
Primary/secondary sludge: dewater (centrifuge/belt press) to 20–30% DS, then compost, incinerate or co-process depending on local rules. Expected dewatered cake ~200–500 kg DS/day (estimate). Pilot and lab dewatering tests required.
Quick summary table (key numbers)
Flow: 500 m³/day
Oil trap volume: ~42 m³ (2 hr detention)
EQ tank: 750 m³ (1.5 day) with drum screen (rated ~25–30 m³/hr)
DAF area: ~3.5 m² (plate pack unit, vendor module for 25 m³/hr)
Primary clarifier: ~22 m² area → choose 6 m dia × 3.5 m depth (vol ~95 m³)
UASB: 625 m³ (HRT 30 hr), CH₄ ≈ 569 m³/day
Aeration tanks (total): 266.7 m³ (two tanks of 133.3 m³ each), total HRT 12.8 hr
Secondary clarifiers: area per clarifier ~40 m² (choose 7.5 m dia) — two trains
Disinfection tank: ~10.4 m³ (30 min contact)
PSF area: ~3.5 m² (2 units parallel)
GAC EBCT volume: ~5.2 m³ (two vessels)
UF area (pre-RO): ~500 m² (vendor modules)
RO membrane area: ~1,444 m² (flux 15 L/m²·hr, 80% recovery)
RO permeate: 400 m³/day; brine: 100 m³/day
Evaporator duty (to evaporate 90 m³/day): ~13,500 kWh(th)/day (planning basis)
Aeration O₂: ~568 kg O₂/day → aeration energy ≈ 227 kWh/day (indicative)
RO electrical: ~1,600 kWh/day (indicative)
Pilot / testing required for RO fluxes, UF flux, DAF performance, evaporator energy and crystallizer solids composition.
Here is a clear, direct and technically grounded solution for designing a Zero Liquid Discharge (ZLD) wastewater treatment system for a 500 KLD slaughterhouse effluent with your given parameters (COD ~5000 ppm, BOD ~2000 ppm, TSS ~2000 ppm, FOG ~1000 ppm). I’ll give you a step-by-step process flow, key technologies to use, and design considerations based on current technologies in industrial wastewater treatment and ZLD design. I’ve included external references for verification.
1 Problem Solver (Generator)
We break down the treatment into stages that work progressively from bulk contaminant removal to fine purification and total water recovery.
Stage A Pre-Treatment and Screening
This stage removes coarse solids, large fats, oils, and greases that damage and foul downstream units.
Key equipment and goals:
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Bar screens and Grit removal: Remove large solids and stones.
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Grease traps and oil skimmers: First capture of free FOG.
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Rotary drum screen (500–1000 µm): Protects pumps and membranes.
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Dissolved Air Flotation (DAF): Removes emulsified fats, proteins, heavy particulates. DAF is a proven solution for slaughterhouse FOG, TSS, and BOD reduction.
Expected outcome:
COD, BOD, TSS and FOG lowered to safer levels for biological treatment. DAF can remove up to ~90% of FOG and ~90% of TSS depending on design.
Stage B Biological Treatment (Main Organic Load Reduction)
Biological processes handle high organic loads and turn them into biomass and biogas where possible.
Options based on world practice:
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Upflow Anaerobic Sludge Blanket (UASB) Reactor: High organic removal and methane production in heavy waste streams. Works well for high COD up to 10 000 ppm.
Output reduces COD significantly before aerobic polishing. -
Aerobic MBBR / SBR Polishing: Handles residual COD/BOD after anaerobic step for improved effluent quality.
Why these?
Slaughterhouse wastewater is rich in organics. A UASB + aerobic combination reduces load efficiently before fine filtration and membrane systems.
Stage C Tertiary Filtration and Polishing
Downstream filtration is critical before membranes and RO.
Technologies:
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Sand filtration to remove finer suspended solids.
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Activated carbon filters to adsorb residual organics.
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Ultrafiltration (UF) to remove residual solids and large organics.
UF protects Reverse Osmosis and reduces fouling risk.
Stage D Membrane Treatment (Reverse Osmosis)
Reverse Osmosis is a central technology for ZLD. It separates clean water from dissolved solids, organics, salts, and other contaminants.
Design practice:
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Two-stage RO:
Stage 1 removes a large portion of TDS/COD.
Stage 2 further reduces dissolved contaminants and helps reduce brine volume. -
Scaling and fouling control:
pH adjustment, antiscalant dosing, and periodic cleaning are essential.
Efficiency:
Modern RO can recover 95 % or more water in industrial ZLD contexts when staged properly and protected with pre-treatment.
Stage E ZLD Concentate Treatment (Evaporation / Crystallization)
After RO, you will have a concentrated brine that still contains dissolved solids. To achieve zero discharge, you must eliminate all liquid discharge.
Thermal technologies:
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Mechanical Vapor Recompression (MVR) Evaporators: Efficient concentration of brine by boiling and recompression of vapor.
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Multi-Effect Evaporators (MEE): Multi-stage boiling stages to improve thermal efficiency.
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Crystallizers: Final conversion of brine into solid crystals.
These produce a solid waste cake suitable for safe disposal or further processing (e.g., fertilizer recovery if nutrient content is present).
Stage F Final Polishing and Disinfection
Treated water after RO should meet reuse quality for plant processes (cooling towers, cleaning, etc.).
Methods:
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UV disinfection for pathogen control.
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Fine polishing filters for final clarity and quality consistency.
2 Judge (Verifier)
Here is why the above scheme is suitable and current:
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Pre-treatment and DAF are industry standard for slaughterhouse effluent. They remove solids and FOG effectively and prevent biofouling downstream.
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UASB + aerobic polishing matches the high organic load typical of slaughterhouse wastewater and boosts biogas production.
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RO and membrane systems are core technologies for ZLD. They enable very high water recovery if protected with upstream filtration.
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Thermal evaporators and crystallization ensure no liquid waste. Without this stage, RO brine remains a liquid discharge which violates true ZLD.
3 Meta Verifier (Meta Verifier / Auditor of the Judge)
Let’s validate the full flow logically:
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Raw slaughterhouse water is high in organics, solids, and fats. Removing these early protects biological and membrane stages.
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Biological units are proven for high COD/BOD loads and are widely used in food industry wastewater.
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Membranes alone cannot eliminate all liquid waste. RO reduces volume significantly, but evaporators and crystallizers remove remaining water to solids.
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ZLD is not a single machine but a sequence of technologies integrated as a system.
4 Summary of Design Steps
Flow Summary:
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Screening and grit removal
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Primary separation (DAF, oil traps)
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Biological reduction (UASB + aerobic)
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Tertiary filtration (sand, carbon, UF)
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Membrane treatment (multi-stage RO)
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Brine concentration and thermal recovery (MVR/MEE + crystallizer)
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Disinfection and final polishing for reuse
Key advantages:
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Achieves true zero liquid discharge.
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High water recovery (95 %+).
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Pathogen and contaminant removal compliant with reuse standards.
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Breaks down and removes FOG, TSS, COD, and organics.
If you want, I can also provide example equipment specs and approximate cost ranges for each stage of a 500 KLD system.
1. Problem Solver (Generator)
Design Basis
Flow 500 KLD continuous
Hourly flow about 21 m3 per hour
Influent COD 5000 mg per L
BOD 2000 mg per L
TSS 2000 mg per L
FOG 1000 mg per L
Target ZLD with internal reuse
2. Process Flow with Equipment Sizing
A. Preliminary and Primary Treatment
Mechanical Screen and Grit Chamber
Purpose is to protect downstream equipment.
Bar screen spacing 10 to 15 mm
Fine rotary drum screen 500 micron
Indicative cost India
₹15 to ₹25 lakh
Industry practice reference
Food and slaughterhouse wastewater guidelines recommend fine screening before DAF and biological systems
Dissolved Air Flotation DAF
This is non negotiable for slaughterhouse wastewater.
Design loading
Hydraulic loading 5 to 10 m3 per m2 per hour
Surface area required about 3 to 4 m2
Expected removal
FOG 85 to 95 percent
TSS 80 to 90 percent
COD 30 to 40 percent
Chemical dosing
PAC or ferric salt plus polymer
Indicative cost India
₹45 to ₹70 lakh including air saturation system and chemical dosing
Reference
DAF is globally accepted as best available primary treatment for slaughterhouse effluent
B. Anaerobic Biological Treatment
UASB Reactor
This is where the real COD reduction happens.
Design loading
Organic loading rate 6 to 8 kg COD per m3 per day
COD load about 2500 kg per day
Reactor volume
About 350 to 420 m3
Hydraulic retention time
16 to 20 hours
Expected performance
COD removal 70 to 80 percent
Biogas generation 0.35 m3 per kg COD removed
Indicative cost India
₹1.2 to ₹1.6 crore including gas holder and piping
Reference
UASB reactors are standard for high strength slaughterhouse wastewater in Asia and India
C. Aerobic Polishing
MBBR or SBR
Either works. MBBR is simpler for continuous flow.
Design parameters
Post UASB COD around 800 to 1000 mg per L
BOD around 300 to 400 mg per L
MBBR media fill
50 to 60 percent
Reactor volume about 250 to 300 m3
Expected performance
BOD less than 30 mg per L
COD less than 200 mg per L
Indicative cost India
₹80 lakh to ₹1.1 crore including blowers and diffusers
Reference
Combined anaerobic aerobic treatment is recommended for food industry wastewater before membranes
D. Tertiary Treatment Before Membranes
Pressure Sand Filter and Activated Carbon Filter
Flow designed for 25 m3 per hour
PSF vessel dia about 1.6 m
ACF vessel dia about 1.6 m
Indicative cost India
₹20 to ₹30 lakh
Ultrafiltration UF
This is critical before RO.
UF capacity
25 m3 per hour
Hollow fiber membranes
Expected SDI
Less than 3
Recovery
95 percent
Indicative cost India
₹70 lakh to ₹1 crore
Reference
UF is considered mandatory pretreatment for RO in ZLD systems
E. Reverse Osmosis System
Two Stage RO
Design recovery
First pass 70 percent
Second pass 75 percent
Overall recovery around 85 percent
Permeate reuse
Process washing
Cooling tower makeup
RO reject flow
About 75 KLD
Indicative cost India
₹1.4 to ₹1.8 crore including high pressure pumps and CIP
Reference
Two stage RO is industry standard for high recovery ZLD systems
F. ZLD Thermal System
MEE with ATFD or Crystallizer
Feed to evaporator
75 KLD RO reject
MEE type
Three effect with TVR or MVR
Final solids
Mixed salts and organics
Moisture less than 10 percent
Indicative cost India
₹3.5 to ₹5 crore depending on MVR or steam driven
Reference
Thermal evaporation and crystallization are essential for true ZLD compliance
G. Final Water Quality and Reuse
Recovered water quality
TDS less than 100 ppm
COD less than 20 mg per L
Reuse applications
Crate washing
Floor washing
Cooling towers
3. Overall Cost Summary India
| Section | Approx Cost |
|---|---|
| Pretreatment and DAF | ₹60 to ₹90 lakh |
| UASB system | ₹1.2 to ₹1.6 crore |
| Aerobic MBBR | ₹0.8 to ₹1.1 crore |
| UF system | ₹0.7 to ₹1 crore |
| RO system | ₹1.4 to ₹1.8 crore |
| MEE plus crystallizer | ₹3.5 to ₹5 crore |
| Electrical automation civil | ₹1.5 to ₹2 crore |
Total project cost
₹10 to ₹13 crore for 500 KLD ZLD slaughterhouse ETP
4. Judge (Verifier)
This configuration is valid because
DAF protects biology and membranes from fats
UASB handles bulk COD efficiently
Aerobic polishing ensures membrane compatibility
UF plus RO gives high water recovery
Evaporator ensures zero liquid discharge compliance
This exact configuration is being implemented in India in meat processing and poultry industries.
5. Meta Verifier (Auditor of the Judge)
If any single unit is removed
No DAF leads to membrane fouling
No anaerobic stage leads to huge power cost
No thermal stage means ZLD is false
So technically and regulatorily this design holds
1. UASB Reactor Design Calculations
Key Design Targets
You want to remove the bulk of COD (say 70–80 %). Typical volumetric organic loading for strong industrial wastewater is 4–12 kg COD/m³·day.
Step A: Organic Loading Rate (OLR)
Choose a design OLR in the middle range for high COD strength.
Example: OLR = 8 kg COD/m³·day
Your influent COD = 5000 mg/L = 5 kg/m³
Feed COD load (per day) =
500 m³/day × 5 kg/m³ = 2500 kg COD/day
Step B: Reactor Volume
Using the OLR equation:
Volume (V) = Q × S₀ / OLR
where S₀ is influent COD in kg/m³, Q is flow in m³/day.
So:
V = (500 × 5) / 8 = 312.5 m³
Round up for safety and retention: 350–400 m³ total working volume
Step C: Upflow Velocity Check
Design upflow velocity must be < 0.5–1.2 m/h to avoid sludge washout.
Upflow velocity (m/h) = Q / reactor cross-section area
If depth ~5 m, area ≈ V / depth → 350 / 5 = 70 m²
Upflow velocity = (500 / 24) / 70 ≈ 0.30 m/h → acceptable
Step D: Effluent and Retention
Typical HRT (hydraulic retention time) for strong industrial waste: 12–20 h. Volume/(flow/24) gives that range.
2. MBBR (Aerobic Polishing) Calculations
Purpose
Polish residual COD after UASB to levels suitable for membranes.
Step A: Organic Load for MBBR
Let’s say UASB removes 75 % COD → residual ≈ 1250 mg/L COD.
Daily residual load = 500 × 1.25 = 625 kg COD/day
Step B: Surface Area Loading Rate (SALR)
Design SALR for BOD/BOD removal often chosen 8–12 g BOD/m²·day.
Assume SALR = 10 g BOD/m²·day
Convert COD to BOD roughly by 2.5 factor (industrial use): residual BOD ~500 mg/L → 250 kg BOD/day.
So required carrier surface:
= (250,000 g/day) / (10 g/m²·day) = 25,000 m² surface
If media specific surface = 500 m²/m³ → carrier volume =
25,000 / 500 = 50 m³ of media.
At 40 % carrier fill: reactor liquid volume =
50 / 0.40 = 125 m³
So design MBBR reactor volume ~125–150 m³.
Step C: Oxygen Requirement
Oxygen demand (stoichiometric for BOD):
O₂ ≈ 1.42 × BOD removed (kg)
= 1.42 × 250 = 355 kg O₂/day
Air required (assuming 20 % oxygen transfer efficiency) =
= 355 / 0.20 = 1775 kg of air/day
Airflow equipment should support this.
3. Reverse Osmosis (RO) Design Calculations
RO design is more standardized — performance is tied to flux, recovery, and membrane area.
Key Definitions
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Recovery (%) = Permeate flow / Feed flow
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Flux (LMH) = Permeate flow (liters/hour) / Membrane active area (m²)
Step A: Design Recovery
For pretreated slaughterhouse water after UF, you can target 80–85 % recovery per train.
Feed = post-UF ~500 m³/day (minus losses).
RO permeate target = 425 m³/day
RO brine ≈ 75 m³/day
Step B: Flux & Membrane Area
Assume design flux = 15 L/m²·h (reasonable for industrial RO)
Convert 425 m³/day to hourly:
425,000 L / 24 ≈ 17,708 L/h
Required membrane area:
= 17,708 / 15 ≈ 1,180 m² membrane area
Typical RO element has ~40 m² → number of elements ≈ 1200/40 ≈ 30–35 pressure vessels in parallel/series staging.
Step C: Pressure Estimation
RO operating pressure must overcome osmotic pressure of feed. For brackish feed (TDS post-pretreatment) and high organics, design pressure ~20–25 bar is typical.
This informs pump sizing.
4. MEE/MVR Evaporator and Crystallizer Calculations
For ZLD you need to concentrate RO reject (~75 m³/day) into solid salts plus recovered water.
Step A: MEE and MVR Concepts
Mechanical Vapor Recompression (MVR) reduces steam energy input by compressing vapor and recycling latent heat. This is state-of-the-art for ZLD evaporators.
Step B: Mass Balance
Feed to MVR = 75 m³/day of RO brine.
Assuming final solids are say 20 % by weight at saturation (approximate for mixed salts), recovered distillate ~80 % of feed.
So distillate ≈ 60 m³/day; concentrated liquor ≈ 15 m³/day.
Further crystallization of 15 m³ at high concentration produces solids. This is approximate; real crystallization depends on salt composition.
Step C: Evaporator Sizing & Energy
MVR evaporator design uses energy balances:
-
Heat of vaporization (latent heat) = ~2250 kJ/kg
-
Compressor work recovers most of the latent heat.
MVR systems for wastewater evaporation often have specific energy consumption 30–60 kWh/m³ of distillate as a design estimate.
For 60 m³/day distillate, total energy ~ 60 × 50 = 3000 kWh/day.
Boiling area sizing depends on temperature difference and heat transfer coefficients and is usually done with standard heat transfer design methods (NTU, LMTD) based on desired evaporation rate.
5. Putting It All Together — Example Summary
| Unit | Example Sizing |
|---|---|
| UASB Effective Volume | ~350–400 m³ |
| MBBR Reactor Volume | ~125–150 m³ |
| RO Membrane Area | ~1,200 m² (30–35 vessels) |
| MVR Evaporator Feed | ~75 m³/day |
| MVR Distillate | ~60 m³/day |
| MVR Crystallizer Output | Salts/solids from ~15 m³/day |
Notes and Practical Points
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Real design requires detailed mass balance with actual influent composition and seasonal variability.
-
Pilot testing or design software (ROSA for RO, vendor specs for membranes, and vendor data for MVR and media carriers) improves accuracy.
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Biological kinetics for MBBR depend on temperature and influent variability, and you should design for worst-case peak loads.
