Biosolids are one of the more challenging materials handled in any industrial conveyor application. Variable moisture content, adhesion tendency, corrosive chemistry, and the continuous operational requirements of municipal wastewater treatment all create design and operational demands that require purpose-built solutions. Here’s a practical overview of the key challenges and how they’re addressed in well-designed systems.
Managing Variable Material Properties
Biosolids moisture content varies based on dewatering equipment performance, feedstock composition, and seasonal factors. A conveyor system designed around a single assumed moisture content will be undersized in wet conditions and oversized in dry conditions.
Good system design accounts for the full range of expected material properties — bulk density, moisture content, adhesion tendency — and sizes drive components, belt width, and speed to handle the worst-case scenario while operating efficiently under normal conditions. The Pathwinder is Serpentix’s most widely specified system for biosolids handling in municipal treatment plants, with material and surface treatments selected for high-moisture, high-wear, and corrosive conditions to keep maintenance intervals low and service life long.
Addressing Adhesion and Carryback
Biosolids’ adhesion properties cause material to stick to belt surfaces and carry back beyond the discharge point. Carryback contaminates the return strand and accumulates under the conveyor, creating cleaning burdens and potential compliance issues.
Belt cleaning systems are typically required in biosolids applications:
- Primary scrapers: Remove the bulk of material at the discharge point
- Secondary scrapers: Address residual carryback on the return strand
- Brush systems: Used in combination with scrapers for difficult-adhesion materials
The cleaning system design has to be matched to the belt type and material characteristics, and it has to be maintainable in the specific site conditions where the conveyor operates.
High-Volume and Continuous Operations
For treatment plants running 24/7 with high biosolids throughput, the Model-H is built for this demand. It handles longer conveyor runs and sustained heavy-duty uptime where a lighter-duty system would require more frequent intervention.
For facilities that need to move biosolids to more than one discharge point — a dewatering press, a storage area, and a loading dock, for example — the Flight Distribution conveyor moves material to multiple discharge points within a single system without interrupting operations.
Discharge Flexibility Without Structural Modification
Fixed discharge locations are a constraint in many existing treatment facilities. The Flex-End Discharge, available on Pathwinder systems, adds multiple discharge points across a 12-foot arc — the preferred specification for facilities where structural modification to accommodate a new fixed discharge point isn’t practical.
Structural and Material Compatibility
The chemical environment around a biosolids conveyor — hydrogen sulfide, ammonia compounds, moisture — is aggressive toward standard carbon steel. Structural components, fasteners, and drive component housings should be specified for corrosion resistance appropriate to the exposure level.
This is a lifecycle cost decision: the upfront cost of appropriate materials is recovered many times over in reduced corrosion-related maintenance and component replacement.
Odor Control Integration
Biosolids conveyors often operate in enclosed spaces or require enclosure for odor control purposes. Enclosed conveyor design has implications for cleaning access, maintenance access, and ventilation that have to be addressed at the design stage.
Enclosure geometry that prevents condensation accumulation, provides access for routine cleaning, and allows belt and component inspection without enclosure removal reduces the operational burden of enclosed conveyor systems.
Serpentix Conveyor Corporation has designed and fabricated biosolids handling conveyor systems for municipal wastewater treatment facilities across the country. Our engineering team has direct experience with the material handling challenges specific to this application. Contact us to discuss your project requirements.
