Why Pea Processing Needs Its Own Design

High Organic Load, Short Processing Season

Pea (matar) freezing and processing lines generate wastewater from blanching, cold-water chilling, washing, and peeling — carrying dissolved sugars, starch, and fine pulp at very high organic strength. Most of this load arrives over a compressed harvest season, so the plant has to handle sharp peak flows rather than a steady year-round stream. Left untreated, the sugars ferment quickly, souring the effluent and stripping oxygen from receiving drains within hours.

At a Glance

Process Flow — Seven Stages, Anaerobic-First

An anaerobic stage does the heavy lifting on very high organic strength before aerobic polishing takes over. Scroll sideways on smaller screens.

Design Basis

Standard Inlet Effluent Characteristics

Typical raw effluent ranges we design around for pea processing blanch, wash, and peeling water.

Parameter	Typical Raw Inlet Range	Rispri Treated Target	Source Stream
pH	6.0 – 7.5	6.5 – 8.5	Blanch & wash water
BOD	1,500 – 4,000 mg/L	< 30 mg/L	Blanching, cooking liquor
COD	2,500 – 6,000 mg/L	< 100 mg/L	Blanching, cooking liquor
Total Suspended Solids (TSS)	800 – 2,500 mg/L	< 50 mg/L	Pea skins, pulp fines
Oil & Grease	20 – 60 mg/L	< 10 mg/L	Processing line washdown
Total Dissolved Solids (TDS)	1,000 – 2,500 mg/L	< 2,100 mg/L (CPCB)	Brine chilling, wash water
Temperature	40 – 55 °C (fresh blanch discharge)	< 40 °C (CPCB limit)	Blanching outfall

Indicative values, generalized from published fruit & vegetable / root-crop processing effluent studies rather than pea-specific data — genuinely pea-specific published figures are scarce. Actual figures vary by throughput, blanch time, and recycling practice already in place, and should be confirmed through site effluent characterization during project scoping.

Compliance

Discharge Standards That Apply

Food processing doesn't have its own dedicated CPCB Schedule VI entry the way dairy or a handful of other sectors do, so the General Standards under the Environment (Protection) Rules, 1986 apply. The IFC/World Bank EHS Guideline for Fruit & Vegetable Processing is a useful international reference point alongside it.

Parameter	CPCB General Standard (Inland Surface Water)	IFC/World Bank EHS Guideline (F&V Processing)
pH	5.5 – 9.0	6 – 9
BOD (3 days, 27°C)	30 mg/L	50 mg/L
COD	250 mg/L	250 mg/L
TSS	100 mg/L	50 mg/L
Oil & Grease	10 mg/L	10 mg/L
Discharge to public sewer	BOD limit relaxed (commonly cited up to 350 mg/L where the receiving sewer has secondary treatment)	Not applicable

The IFC guideline isn't a legally binding Indian standard, but it's a common benchmark for export-oriented processors and lenders. Your State Pollution Control Board's Consent to Operate governs what actually applies at your site.

Process Design

The Treatment Process Rispri Follows

An anaerobic-aerobic biological train sized to knock down very high BOD/COD economically, ahead of polishing and reuse.

01

Screening

Rotary drum or vibrating screen removes pea skins, pods, and coarse pulp before the flow reaches equalization.

02

Equalization & Cooling

An equalization tank buffers the sharp seasonal flow and load swings from blanching batches, while cooling brings hot blanch discharge down before biological treatment. Standard practice sizes equalization for at least a full day of peak-season flow, since agri-processing effluent is explicitly called out in wastewater engineering guidance as unpredictable in BOD, pH, and flow due to harvest scheduling.

03

Primary Settling / DAF

Dissolved Air Flotation or a primary settling tank removes fine suspended solids, starch colloids, and floating material ahead of biological treatment — protecting the anaerobic stage from solids overload.

04

Anaerobic Pre-Treatment (UASB)

An Upflow Anaerobic Sludge Blanket reactor is the workhorse stage for high-strength organic load like blanching and cooking liquor. Published case studies on comparable food-processing effluent report UASB reactors run stably at organic loading rates of roughly 2.5–7 kg COD/m³·day, with well-designed systems achieving 70–90%+ COD removal — and starch-heavy wastewater specifically has shown up to 81–99% COD removal at optimized loading in published trials. Over two dozen full-scale UASB installations run in the closely comparable potato-processing sector.

05

Aerobic Biological Treatment

MBBR, SBR, or extended aeration polishes residual BOD/COD down to discharge norms. MBBR systems on food-processing effluent are typically designed around 6–10 kg BOD/m³·day loading, and a published food-industry MBBR retrofit ahead of an SBR cut carbonaceous BOD by more than 75% before the SBR stage even started.

06

Clarification & Sludge Dewatering

Secondary clarifier settles biomass; excess sludge is dewatered on a filter press for disposal or composting — pea-processing biosolids are largely organic and compost well where local norms allow.

07

Tertiary Filtration & Disinfection

Sand and carbon filtration with chlorination readies treated water for safe discharge or reuse in washdown, gardening, or cooling makeup.

Biogas Recovery Potential

The UASB stage doesn't just remove COD — it converts a meaningful share of it to biogas. Anaerobic digestion studies on food/vegetable-processing wastewater report methane yields in the range of roughly 0.25–0.29 L CH₄ per gram of COD removed, and full-scale food-processing anaerobic systems have reported recovering somewhere in the range of 35–68 m³ biogas per m³ of wastewater treated at 80–90% COD removal. Whether recovered biogas is worth capturing and using (boiler fuel, captive power) depends on your plant's flow and season length — it's a sizing conversation we have during design, not a default assumption.

Handling the Seasonal Swing

Pea processing runs a short, intense harvest season rather than steady year-round flow. That means the UASB and equalization stages are sized to the campaign-season peak, not the annual average — and standby aerobic capacity or a flexible loading strategy matters more here than in a continuous-flow food plant. This is one of the clearest cases where a generic ETP sizing spreadsheet undersizes the plant if it's built around average daily flow instead of peak-season flow.

Frequently Asked Questions

Why anaerobic treatment first, instead of going straight to aerobic?

Aerobic treatment on very high-COD effluent means a lot of aeration energy to supply oxygen for that organic load. An anaerobic UASB stage removes the bulk of the COD without aeration — and generates usable biogas in the process — leaving the aerobic stage to handle a much smaller, more manageable polishing load.

Can the plant handle the off-season when there's little or no flow?

UASB sludge granules need to stay viable through the off-season, which is a real design consideration for seasonal plants — low-flow maintenance dosing or partial recirculation is typically built into the operating plan so the reactor doesn't need to be reseeded every season.

Is pea-processing wastewater safe to treat and reuse for irrigation?

After full treatment (anaerobic + aerobic + tertiary filtration/disinfection) to discharge-norm quality, treated water is commonly suitable for non-potable reuse such as gardening or washdown. Direct irrigation reuse needs its own sign-off against local agricultural water-quality guidance, which is a separate conversation from meeting CPCB discharge norms.

Sources: IFC/World Bank EHS Guidelines — Fruit and Vegetable Processing, ScienceDirect — fruit/vegetable processing wastewater characterization, MBBR loading-rate engineering reference, MDPI — anaerobic digestion biogas yield studies. Genuinely pea-specific published data is limited; most figures above are generalized from potato, carrot, and general fruit/vegetable processing effluent studies as the closest documented analogs, and are flagged as such rather than presented as pea-specific findings. CPCB limit figures should be cross-checked against the current primary CPCB PDF before being used for compliance decisions.

Why This Matters for Pea Processors

Handles compressed harvest-season peak loads without overflow
Anaerobic stage recovers biogas potential from high-strength organics
Prevents souring/odour from uncontrolled sugar fermentation
Designed to CPCB/SPCB norms for food processing discharge

Typical Plant Configuration

Screening + equalization sized for seasonal peak flow
UASB reactor sized on kg COD/day, not just flow
MBBR/SBR polishing stage with standby capacity for peak season
Filter press for biosolids dewatering

Water Treatment for Pea Processing Plants