Clearford holds 26 issued or pending patents on the Small Bore Sewer™
At no other point in modern history has the thought of water scarcity and availability been such a prominent part of main stream thought. That being said, the earth has approximately the same amount of water today, as it has since its creation. The problem is the availability of clean water, as clean water has been one of the many victims in human and technological evolution. To amplify the growing issues, the exponential growth of urbanization leads to a per capita water use that is less than what is required for the successful operation of the historic gravity sewer. In order to successfully get through what we will soon call a crisis, the world needs to properly manage the remaining resources and begin to implement solutions that allow for the reclamation of water used, and use solutions that allow for the creation of assets from liabilities. The Clearford SBS™ system takes raw sewage and delivers clean water and green energy.
The importance and impact that at-source gravity separation of solids has on wastewater servicing can easily be lost on those unfamiliar with sewage treatment. At-source, solids segregation of the sewage provides two waste stream components with many advantages: conveyance of supernatant and sludge digestion.
Smaller diameter, economical pipes:
- Valuable water resources are not wasted for the purpose of floating solids downstream in large, oversized pipes. Instead, the SBS™ system is installed with economical small diameter pipes because it conveys only supernatant. The effluent stream contains no solids that can become lodged in the pipe and the system has the additional advantage of not requiring high volumes of water to flush out obstructions that occur in conventional whole sewage systems. Additionally, SBS™ pipes are sealed to prevent additional inflow or infiltration into the network, ensuring consistent operation and maintenance costs – the lowest of any sewage system – and budgeting accuracy based on operation history of existing systems.
- Whereas, conventional whole sewage gravity sewers require steep pipe slopes of up to two percent (20 m of sewer elevation depth for every 1000 m of pipe) to create sufficient sewage velocity to scour the pipes, solids-free SBS™ effluent sewers can be installed at shallow gradient slopes (1.5 m for every 1000 m), keeping the system shallow buried throughout the servicing area and reducing significantly the need for frequent pump stations to bring the pipe system’s effluent back to minimum cover near grade.
- Shallow gradient SBS™ effluent sewer installations are significantly less costly than deep conventional whole sewage systems. Because pipe installation costs increase exponentially the deeper the pipe installation, SBS™ systems eliminate the need for heavy equipment and trench boxes for deep excavations.
- Because the slope of the SBS™ system piping is less steep, the overall elevation drop of the system is significantly less per building serviced and requires only native soil to provide physical protection to the underground pipe.
- Traditional whole sewage pipe networks are sensitive to solids depositions that cause blockages and to avoid these blockages the piping design requires straight alignment and few slope changes. This inflexibility to design layout makes conventional whole sewage systems rigid, expensive and inefficient to construct when compared to SBS™ effluent sewer design that is not encumbered by curvilinear alignment, inflective gradients and sharp slope changes.
- Corrosion prevention/control is a design feature of the SBS™ effluent sewer. Slower moving solids-free effluent have less air entrainment within the system, with the result that corrosive acids delivered to downstream infrastructure will be equal to or less than turbulent whole sewage conveyance systems.
- The SBS™ ™ is shallow buried, at a target depth of 0.5m to 2.0m, using local manpower and hand tools for trenching.
- The alignment of the SBS™ effluent sewer system’s pipe network is forgiving. If alignments and/or elevations are not perfect, the system will function successfully with sharp bends or inflective gradients. Trenching and tank installation can be performed by local laborers. Fusion training required to join the pipe sections together can take place in a few hours.
- The vessel tank not only segregates solids but also buffers peak flows and provides a consistent, attenuated flow to the treatment plant. Proprietary attenuation devices supplied by Clearford further enhance flow buffering. By not over-sizing the downstream pump stations and treatment plants, as is required with most other sanitary sewer systems due to the high peaking factors, the entire system has lower initial capital investment and lower ongoing operational costs.
In order to accelerate anaerobic digestion, increase bio-gas production rate, and cause the accessible organic mass to be eliminated, Clearford has developed a non-mechanical method of increasing hydraulic mixing within the Clearford Vessel vessel.
Historically, the inlet device for septic tanks has the purpose of dissipating the energy of sewage as it enters into the vessel. By slowing down incoming sewage, it is able to stratify much easier and thus prevents solids from mixing within the tank; in septic tanks, the purpose is simply to separate solids and liquids, and ensure that minimal solids are discharged into the subsequent tile field, typically only 20% suspended solids. Stratification and maximum solids removal serves the purpose of protecting the tile field; Clearford can support a higher fraction of suspended solids. Without the hydraulic mixing and accelerated anaerobic digestion that Clearford accomplishes, septic tanks must be pumped out every 2-5 years.
The Clearford vessel has a patented inlet device that allows the incoming sewage to harness the energy to effectively create gentle hydraulic mixing of the sludge blanket within the Vessel. The inlet device has an increase in velocity at the entrance of the tank.
Bacteria that have aged in the bottom stratum of the septic tank are excellent at consuming available organics in the sewage; however, these bacteria become enclosed in layers of sludge and cannot access the organic materials in new sewage. Allowing the energy of the incoming sewage to be harnessed to mix the sludge blanket within the tank, the bacteria colonies that develop and mature over the life of the vessel have access to the new sewage.In the picture above, the left drawing illustrates a septic tank’s flow pattern, and the picture on the right illustrates the expected flow pattern in a Clearford vessel. Green is zero velocity or “dead zones”, the dark red and blue coloration shows high velocity in opposite directions and hydraulic mixing in the vessel as a spinning motion on the diagram. As can be seen, within the Clearford vessel, there is a substantial increase in movement and velocity in the tank.
The inlet that creates the passive hydraulic mixing is one aspect of the Vessel that differentiates it from a septic tank; another is the patented attenuation device, which allows for a hydraulic retention time of up to 3 hours of flow retardation.
The graph above shows the various attenuation devices tested during research, and their hydraulic retention time. The blue Control Test was without an attenuation device, which would represent a similar retention as a historic gravity sewer or septic tank. The test run #4 represents the attenuation device selected and which is now used by Clearford. Historic Sewers cannot store flow and must be able to pass the highest expected flow on any day. Attenuation, or peak shaving, of a flow translates into lower peak/design flows, smaller pipes, and installation slopes and smaller receiving infrastructure. This attenuation within the vessel translates to a reduced peaking factor for system sizing. This is illustrated below:
In order to ensure that the sewer piping network and wastewater treatment plants are large enough to handle the regular working flows of a community, they must be designed to service the community peak flow. For historic sewer systems the peaking factor are designed for between 2 and 4 depending on the community population. Actual peaking factor can be much higher; illustrated above is the peaking factor of 3. The Clearford Small Bore Sewer system with the patented attenuation device achieves hydraulic retention to design for a peaking factor of approximately 1.4. This translates into direct cost savings as the treatment plant and pipes can be reduced by approximately 50%.
The SBS™ effluent sanitation system is itself suited to any region, including dry/low water usage regions; furthermore, the unique methane capture capability of the sewage collection system can function anywhere. The conversion of sewage solids into gas through passive biological action not only digests the solids but also converts a waste product normally considered a hazard into a valuable resource – usable methane gas. The capture and combustion of this greenhouse gas (GHG) has a twenty-one times (21x) reduction in GHG emission impact from methane when compared to equivalent carbon dioxide gas impact.The methane capture system has several design features:
- Simple elegant system design requires no valves or instrumentation in the vessel tank that could otherwise fail. Specialized venting system separates the tanks’ headspaces containing atmospheric air, the supply of which prevents hydraulic lock in the pipe network, from the biogas collection zone through passive hydraulic seals. No interaction between oxygen in atmospheric air with methane gas occurs.
- Passive pressurization of biogas within the vessel tank provides the motive forces to convey biogas to collection hubs or methane conversion facility.
- Vessel tank for hot climates taps into passive thermal energy capture and conveyance to the sludge blanket through conductive and convective heat transfer, thereby providing an optimal bacterial colony zone for sludge degradation and biogas production.
- System access points (SAP) are designed at strategic points on the system to provide air into the system. Additionally, biogas collection system moisture traps installed along the piping network return excess moisture into the SBS™ effluent sewer system.