Sewage Sludge Organic Fertilizer Production Line: Complete Turnkey Solution for Municipal Wastewater Treatment

Project Overview

Municipal Wastewater Treatment — a municipal wastewater treatment authority in South China commissioned a turnkey sludge organic fertilizer plant to convert dewatered sewage sludge and yard waste into certified organic soil amendment. The line was designed for an initial capacity of 5–8 tons per hour. Shenghong Heavy Industry supplied the complete production line including thickening mixing, deep fermentation, stirring tooth-drum granulation, drying, cooling, screening, coating and automatic packing.

Key Challenges

The client faced three core issues:

• Heavy metal and pathogen concerns — regulatory requirement for complete pathogen elimination (temperature >60°C sustained 7+ days) and heavy metal immobilization.
• High fiber content — mixed sludge with yard trimmings creates fibrous feedstock that plugs conventional disc pan granulators.
• Acidic corrosion risk — decomposing organic acids from sludge can corrode standard equipment components.

Complete Plant Process Flow

The Shenghong turnkey line comprises the following stages:

1. Thickening and mixing: Dewatered sludge (moisture ~60%) is blended with yard waste, straw and wood chips by a B500 belt conveyor system. Ratio adjustment achieved via a B650 multi-material auto-batching system to reach 30-40% moisture for granulation.
2. Formulation mixing: Pre-mixed material enters a SH1000x2000 spiral ribbon mixer where commercial microbes, bulking agents and mineral stabilizers are thoroughly blended.
3. Deep fermentation (in-vessel): Material enters an in-vessel fermentation tank with forced aeration. Temperature reaches 65-75 °C over 5-7 days, achieving complete pasteurization and odor reduction meeting Class A biosolid standards.
4. Drum granulation: Fermented material enters the Stirring Tooth-Drum Granulator (typically SH1.5x6 or SH1.8x7). The unique combination of mechanical stirring force and rotating drum action continuously mixes, granulates, forms balls, compacts and polishes powdery materials within the machine. Rubber-lined drum body prevents corrosion from acidic sludge decomposition products.
5. Rotary drying: Wet granules pass through a SHG10100 rotary dryer, reducing moisture to below 15%.
6. Rotary cooling: Hot dried granules cooled to ambient temperature by a GL series cooler drum.
7. Sieving: Oversize granules crushed and returned; undersize fines recycled via a 1.2x4.0 rotary screener.
8. Coating: Nutrient film applied in a 1000x3000 drum coater.
9. Packing: Finished granules bagged by BLD-K50/S automatic packer (25 kg/bag).

Main Equipment Configuration

Why Drum Granulation for Sludge?

For sewage sludge organic fertilizer, the Stirring Tooth-Drum Granulator offers distinct advantages:

• Rubber-lined drum body — prevents corrosion from acidic organic acids released during sludge decomposition, extending service life dramatically.
• Handles 100% pure organic content — no binder required — particles grow under controlled force to form dense spherical pellets.
• No blockage — continuous stirring action prevents fibrous sludge from plugging internal mechanisms.
• Class A compliance — granulation temperature combined with upstream fermentation ensures complete pathogen elimination.

Plant Specification Snapshot

About This Solution

Every Shenghong production line is engineered to the client's raw material, site layout and budget. Whether you work with municipal sludge, pond dredging, food waste or agricultural residues, our engineering team will design a customized line from pre-treatment through packing.