• Home
• Forms
  General Contact Form Biological Treatment Background Form Wastewater Sample Request Distributor Application DAF Request Evaporation Project Produced/Frac Water Treatment Form Restaurant Scrubber Form Reverse Osmosis Form Wet Scrubber Pollution Control Form
• Contact Us
• About Us
• Calculators
  Chemical Preparation and Operating Parameters Jar Testing Parameters Filter Press Sizing Application Flat Bottom Liquid Tank Volume Mesh / Micron Sizing Table Standard Cubic Feet per Hour (SCFH)
• Site Map
• Search Site

Bio-Clear Treatment Systems > Bio-Treat (DSS) Deep Shaft Sludge Digestion

The Bio-Clear (DSS) auto-thermophilic aerobic sludge digestion process uses a submerged hyperbaric aeration system, which has been proven effective through more than 20 years of commercial operation in biological processes.

Process Summary

Sludge is digested in a sub-surface auto-thermophilic reactor, typically 150-300 ft deep. The vertical reactor has 3 distinct zones: Oxidation Zone: The top portion of the shaft where the majority of the sludge digestion takes place. Mixing Zone: Feed sludge and air are introduced in the reactor mixing zone. The air provides oxygen for solids reduction, promotes mixing in the reactor, and achieves solids separation through flotation thickening. Saturation Zone: Stabilized biosolids withdrawn from the reactor flow down through the saturation zone where high temperature and long residence time ensure that Class A biosolids are produced. Class A biosolids are withdrawn from the bottom of the reactor and transferred to a thickener where rapid depressurization of the gases dissolved at depth results in effective solid/liquid separation through flotation. Off-gas is separated from the circulating liquor in the head tank and is treated in a fixed-film biofilter.

Bio-Clear (DSS) Key Features

The Bio-Clear Deep Shaft Sludge digestion system is a state-of-the-art aerobic thermophilic process that converts municipal primary and secondary sludge's to Class A Biosolids, as defined by EPA, CFR-503. It uses an in-ground hyperbaric aeration reactor; a device that has been proven effective through more than 25 years of commercial operation in biological processes. The Bio-Clear (DSS) reactor’s patented design features give it the following advantages over conventional ATAD and anaerobic systems:

• A treatment plant with a Bio-Clear (DSS) system and subsequent dewatering will typically produce 50% less sludge volume than a plant with dewatering alone.
• VS reductions of 40% to 45% are readily obtained with a 4-day detention time, and a 7-log reduction in pathogens is achieved, guaranteeing that EPA requirements for Class A biosolids are met.
• The decanted product thickens to approximately 10% solids and dewaters readily to 30% to 35% solids with minimal polymer addition. Low polymer consumption and reduced trucking and disposal costs that result from the high solids content, give significant operating cost savings over conventional ATAD processes.
• Heat is recovered from the process using inexpensive heat exchangers and can be used to heat buildings without installing the expensive gas cleaning systems and boilers required to recover heat from anaerobic processes.
• Overall capital cost is lower than conventional processes in most applications.
• Due to the pressure in the shaft, the process has enhanced oxygen transfer, lowering the operating costs due to a lower power requirement than conventional aerobic digestion processes.
• The system is very compact and has a low space requirement, usually less than 20% of the space used by conventional processes. The subsurface nature of the aeration shaft results in very compact, low visual impact systems.
• The system can be economically enclosed in a building in locations where climatic conditions are unfavorable or if it is desirable for the plant to blend architecturally with the surrounding environment.
• The low aeration requirements and enclosed nature of the process help eliminate nuisance odors, and significantly reduces the potential for foaming. Odor, VOC, and ammonia emissions are minimal compared to conventional processes.
• The system is uncomplicated, easy to operate and maintain, and well suited to fully automated unattended operation.
• The leak tight aeration shaft casing, comprised of steel and surrounded by cement grout, eliminates any chance of ground water contamination.
• The submerged aeration shaft is much safer in an earthquake, and less likely to sustain damage than above-ground aeration basins and lagoons.

Comparison of the Bio-Clear (DSS) process to conventional technologies

Technology	Product	VS Removal	Cake Solids	Major Off-Gas	Land Use
Bio-Clear (DSS)	Class A Biosolids	> 40% (<4 day SRT)	> 30%	CO2 , O2 , TRACE NH3	Low
Auto Thermophilic Aerobic Digestion	Class A Biosolids	40% (8-12 day SRT)	25-30%	O2 , CO2 , HIGH NH3	Medium
Temperature Phased Anaerobic Digestion	Class A Biosolids	~60% (>20 day SRT)	15-25%	CH4 , CO2 , H2S	High
Anaerobic Mesophilic	Class B Biosolids	~55% (>25 day SRT)	15-25%	CH4 , CO2 , H2S	High

Applications

The Bio-Clear (DSS) process is ideal for treating sludge from a Bio-Clear (DSA) systems or from conventional biological treatment plants treating municipal sewage or industrial wastes. It is suitable for greenfield sites or can be used to expand existing facilities by incorporating it as an aerobic pre-treatment before conventional digestion systems. It has particular advantages in applications with the following conditions:

• Applications in which Class A Biosolids are required
• Sites with high sludge disposal and/or trucking costs
• Sites with space constraints
• Retrofits and plant expansions
• Sites with high precipitation or extreme temperatures
• Sites close to residential areas or where large unsightly plants are undesirable

Core Reactor Features

The principal difference between Bio-Clear (DSS) and and conventional ATAD systems is its in-ground hyperbaric aeration reactor. Installed by conventional drilling techniques, the Bio-Clear (DSS) reactor is typically 110 m (350 ft) deep, occupying only a fraction of the area used by conventional surface digestion systems. The diameter of the reactor, which can range from 0.75 m to 3 m, (2.5 ft to 10 ft) is determined by the quantity of sludge treated. The Bio-Clear (DSS) reactor has three separate treatment zones:

• The oxidation zone is the upper portion of the reactor and includes a central concentric draft tube for circulation.
• The mixing zone is immediately below the oxidation zone. Air required for bio-oxidation within the upper zone is injected into the mixing zone. The injected air also provides airlift circulation.
• The lower plug-flow zone provides the high-temperature residence time required to kill pathogens such as salmonella and fecal coliform, ensuring that the product meets the Class A Biosolids requirements set forth by the EPA in CFR-503.

Process Description

1. Screened sludge feed is delivered into the mixing zone where it is mixed with partially digested recirculating sludge.
2. Compressed air is continuously added below the mixing zone to provide the oxygen required by the microorganisms to digest the sludge. The high hydrostatic pressure ensures a high oxygen transfer rate.
3. Air bubbles rising up the outer annulus create circulation up the annulus, into the head tank, and down a central draft tube.
4. Off-gas containing excess air and carbon dioxide formed by microbial respiration disengages in the head tank and vents through a feed tank or off-gas biofilter which effectively breaks any foam and removes odors.
5. A small fraction of the recirculating sludge moves from the mixing zone into the lower plug flow zone of the reactor where residual organic materials are digested and high temperature ensures that pathogens are destroyed.
6. Digested sludge is withdrawn from the bottom of the reactor through a central discharge pipe and transferred rapidly to a product tank at the surface.
7. The rapid depressurization of the digested sludge as it travels to the surface causes the solids to separate in the product tank by flotation, and yields Class A Biosolids pre-thickened to around 10% solids. The subnatant liquid is recycled back to the sewage treatment plant for processing prior to discharge.