Clearford One™ – How it Works



Clearford One™ delivers a better approach to sanitation. The key to enabling the efficiencies of Clearford One™ is on-site removal of sewage solids and digestion of organic pollutants in ClearDigest™ smart digester tanks.

ClearDigest removes solids at the source, performing primary and partial secondary treatment before releasing liquid effluent to the ClearConvey pipe network. Solids are digested to greatly reduce the volume of organic material and hydraulic loading. ClearDigest is only pumped out after decades of normal use.

ClearConvey™ is a network of small bore sewer pipes that carries liquids without any infiltration to an optimized facility for final treatment. Reduced contaminants in the liquid effluent allows for more efficient recovery of clean water using the ClearRecover™ treatment package.

ClearRecover is a treatment facility right-sized to match the reduced hydraulic loading and effluent characteristics from ClearDigest. It can take different forms depending on local conditions, ranging from a membrane bioreactor (MBR) to an engineered wetland.

Clearford OneTM System Diagram



ClearDigest™ smart digesters are buried tanks that receive raw sewage from each connected source. ClearDigest™ tanks retain the solids, decompose the biosolids, modulate the flow, and release solids-free effluent by gravity to the ClearConvey™ pipe network. A proprietary inlet device uses the kinetic energy of the inflow to gently mix sewage in the tank to enhance digestion. A patented outlet device allows the water level in the tank to increase during peak use while restricting the outflow from the tank to a modulated rate.

ClearDigest™ effectively performs all of the primary treatment (settling) and much of the secondary (biological) treatment, reliably removing 75% of suspended solids and 65% of biochemical oxygen demand (BOD) from raw sewage. The liquid effluent from ClearDigest™ is substantially solids-free with consistently lower pollutant levels than raw sewage. This enables the efficient conveyance of liquid effluent in ClearConvey™ small bore sewers, and significantly simplifies treatment operations at the ClearRecover™ treatment plant.
Furthermore, the effect of modulating the flow is significant—it reduces the need to oversize downstream collection and treatment infrastructure by as much as 50% compared to conventional sewage systems. The result is smaller pumps, smaller tankage, and smaller footprint for sanitation infrastructure. Flow modulation also normalizes pollutant loading in the liquid effluent and eliminates shock loading to the treatment plant. This allows the final optimized treatment package to target the specific effluent character for efficient treatment.

While ClearDigest™ is highly efficient at decomposing biosolids in raw sewage, non-biodegradable solids are left to accumulate in the smart digesters. However, the tanks require pumping only after decades of normal use. For this frequency of maintenance, the lifecycle cost for operating the Clearford One™ system is minimized.


ClearConvey™ is a small bore sewer tailored specifically for the efficient conveyance of liquid effluent from ClearDigest™ smart digesters. Since the liquid effluent is substantially solids-free, small-bore-sewer pipes are optimized for flow conveyance rather than solids carrying. ClearConvey™ uses small diameter pipes that can be laid with very low and variable slope. The use of flexible plastic pipe allows for streamlined flow in the sewer network, and there is no need for large manholes for maintenance access.

Whereas conventional sewers need large pipes to accommodate sewage solids and peak flow, ClearConvey™ uses substantially smaller pipes—in cases, three times smaller than conventional sewers. This is because ClearDigest™ smart digesters are so effective at removing solids and modulating the flow.

ClearConvey™ relies on gravity to move liquid effluent through the small-bore-sewer pipe network. However, the pipe slope requirement is reduced by up to 50% compared to conventional sewers because ClearConvey™ is not required to move large solids down the sewer pipe. When sewage pumping is required, ClearConvey™ may use only a third of the pump stations required in a conventional system. Furthermore, pumping is simplified by the use of smaller pumps that are only required to handle liquid effluent, not messy sewage solids. This reduces energy use, as well as capital and maintenance requirements.

ClearConvey™ uses flexible, durable high-density polyethylene (HDPE) pipes with fused joints and watertight access points that eliminate extraneous flow to the system. In conventional sewers, leaky joints in pipes and manholes are a significant cause of inflow and infiltration of groundwater that reduce the conveyance capacity of the system and add pumping and treatment costs for downstream infrastructure. Leaky joints may also allow sewage to pollute valuable soil and groundwater resources.


The ClearRecover™ treatment plant is optimized to take full advantage of the unique features of the Clearford One™ system. ClearRecover™ acts as a final polishing step for removing sewage pollutants, leaving clean water that can be reused in the community or released back to the environment. The treatment facility is fully customizable to suit the site requirements for plant configuration, treatment quality and budget. Treatment requirements may be driven by local regulations, as well as the suitability of certain treatment technologies to meet local conditions for equipment supply, construction techniques, and availability of skilled workforce. Deployments of ClearRecover™ range from constructed wetlands to compact state-of-the-art membrane bioreactors.

The combination of ClearDigest™ smart digesters and ClearConvey™ small-bore-sewer pipe network significantly reduces the hydraulic and pollutant loading to the ClearRecover™ treatment plant. The modulation of flow from ClearDigest™ greatly reduces peak hydraulic loading to the treatment plant, resulting in as much as 50% smaller equipment and tankage compared to conventional plants. Sizing is further reduced by the elimination of extraneous flow to the ClearConvey™ pipe network. ClearRecover™ fits into half the footprint of conventional treatment plants, requiring less land and reduced maintenance costs.

ClearRecover™ treatment operations are simplified compared to conventional plants. The sewage needing treatment contains 75% fewer suspended solids and 65% less biochemical oxygen demand (BOD) than raw sewage, thanks to pre-treatment in ClearDigest™ smart digesters. Pollutant loading is normalized to a consistent effluent character that is targeted for efficient final treatment at the ClearRecover™ plant. ClearRecover™ does not require extensive headworks and primary treatment—there are substantial capital and operating cost savings associated with elimination of screening, grit removal and primary settling. Sludge production is reduced compared with conventional plants because most of the pollutants are captured in ClearDigest™ smart digesters. Furthermore, biological treatment is targeted to specific pollutants such as nutrients (nitrogen, phosphorus) for more efficient use of treatment infrastructure and greater environmental protection.

ClearRecover™ achieves the highest quality when paired with UV Pure’s patented Crossfire Technology®. Treated effluent can be sterilized to non-detect pathogen levels using this highly efficient ultraviolet (UV) disinfection technology, making the effluent safe for reuse in non-potable applications like toilets and irrigation.