ETP for Biscuit Manufacturing

Biscuit and cookie manufacturing is one of India's largest food processing sub-sectors, with major players including Britannia Industries, ITC (Sunfeast), Parle Products, and international manufacturers like Lotte India and Pladis. Spans Envirotech has designed and commissioned ETPs for biscuit manufacturers across India, including reference installations at Britannia Industries and Lotte India — giving us deep familiarity with the specific effluent challenges this industry presents.

Biscuit manufacturing generates a complex, variable effluent stream that differs in important ways from generic food processing wastewater. The effluent originates from multiple sources: dough mixing and sheeting machine washdowns contain residual starch, flour, and shortening; baking tunnel oven cleaning generates hot, greasy effluent with combustion residues; cream sandwich and chocolate enrobing lines introduce high concentrations of vegetable fat, cocoa butter, and dairy solids; packaging line cleaning and reject product disposal add to the organic load; CIP (Cleaning-in-Place) cycles with caustic and acid chemicals create pH swings from pH 2 to pH 13 within the effluent equalisation period.

The combined result is an effluent with BOD typically 800–3,500 mg/L, COD 1,500–6,000 mg/L, TSS 300–1,200 mg/L, and fats and oils 50–500 mg/L depending on product mix. Cream biscuits and high-fat snack products generate significantly more FOG load than plain biscuits. The FAT load is the critical design challenge for biscuit ETP — if fats are not removed upstream of biological treatment, they coat MBBR carriers or activated sludge flocs, inhibit microbial activity, and cause biological treatment failures that result in non-compliant effluent.

Spans' standard ETP process for biscuit manufacturing begins with a coarse screen and fat trap to remove gross fat and food solids, followed by an equalisation tank designed for 12–20 hours of HRT to balance the highly variable flow and load. The equalized effluent then feeds a Dissolved Air Flotation (DAF) unit with coagulant and polyelectrolyte dosing, achieving 80–95% removal of fats, oils, greases, and a significant fraction of suspended solids. The DAF effluent — now with BOD 300–700 mg/L and TSS <200 mg/L — feeds the MBBR biological treatment stage.

The MBBR system for biscuit factory ETP uses high surface-area polyethylene carriers (K5 or K3 media, 800–1,200 m²/m³ specific surface area) suspended in an aerated tank, maintaining a dense biofilm that degrades dissolved BOD and COD from DAF outlet levels to <50 mg/L. MBBR is preferred over conventional activated sludge for biscuit ETPs because its fixed biofilm is more robust against the fat contamination and load variation characteristic of this industry. After MBBR, a secondary clarifier (or membrane separation for MBR configurations) polishes the effluent before tertiary pressure sand and activated carbon filtration to achieve BOD <30 mg/L, COD <250 mg/L, and TSS <100 mg/L.

Sludge management is an important aspect of biscuit ETP design. DAF generates a fat-rich flotate sludge (2–4% solids) that is separately collected and thickened. Biological excess sludge from MBBR secondary clarifier is combined with DAF sludge and dewatered using a volute screw press or belt filter press to 18–22% dry solids. Dewatered sludge cake from food processing ETP is non-hazardous and can be composted or sent for landfill disposal. Grease sludge from fat-rich biscuit plant ETPs may be suitable for co-processing in cement kilns.