Operation and Maintenance

The BIODISK has several unique properties making it a desirable system for ease of operation and maintenance such as:

• Low power consumption
• No field tests
• Long-term biosolids (sludge) storage
• No odour
• Built-in multi-stage process utilizes naturally occurring microbes
• Low operator skill requirements
• Operator intervention is limited to preventative maintenance and periodic sludge withdrawal

Low Power Consumption: The BIODISK process requires less electrical energy than other treatment processes. The installed horsepower (hp) ranges from ¼ hp to less than 10 hp. The installed hp is required for start up
only. When in operation the power draw is just 60% of rated capacity. During normal operation
the balanced shaft rotates effortlessly. The shaft power draw is consistent and fluctuates only when start up is required. The rotational speed of the disks is just 1 ft per min. Slow speed is naturally associated with lower power requirements.


There is no requirement to remove or treat the biosolids that are contained within the process. The internal storage of biosolids is essential to the process. Biosolids, when stored in the primary and final tanks, provide a source of heat. The sludge blanket is exothermic and static. No sludge collection devices are required. Sludge is removed once or twice each year. The BIODISK uses a recycle system that puts oxygen into the primary tank. This oxygen recycle eliminates nuisance odours from the primary tank and allows long-term biosolids storage. The recycle also ensures that a food source is available to the biological population 24 hours a day and 7 days a week.


Even accessory items have low power requirements. Phosphorous is removed with the addition of a fractional hp chemical feed pump that proportionally feeds the chemical in relation to the flow. When lower effluent qualities are required the biosolids are returned to the primary sedimentation tank by a fractional hp submersible pump. The frequency of return is only three times a day and for short periods. The control panel allows the owner/operator to adjust the frequency and duration of the biosolids return rate.


The operational cost of the BIODISK is lower than for other forms of treatment processes. The lower power requirement will also save capital if stand by power is a requirement. The low hp in the BIODISK will be reflected in the reduced size stand-by generator requirements.


No Field Tests: The BIODISK processes regulates itself. When the owner/operator becomes familiar with the system, visual inspection is all that is required. When we talk about wastewater we think of pollution. In the BIODISK, pollution is considered a food source for the biological population. The biomass is a living matt of activity that attaches itself to the slowly rotating disks. Microbes that are naturally present in the wastewater accomplish the purification. These microorganisms are often called bugs for simplicity. The bug population is directly related to the food source. If there is a lot of food the bug population will occupy a lot of disk surface area. When the flow or source of pollution is reduced, the bugs or biomass is reduced. This is a natural process that we do not need to influence.


The RBC process does not need to artificially over populate the aeration process. There is no requirement to test for mixed liquor suspended solids (MLSS). There is also no need to calculate the sludge volume index (SVI). The slow rotation of the disk provides a large wetted surface area and efficient oxygen transfer.
Higher than required dissolved oxygen (DO) levels are normally present. High DO eliminates odours and does not inhibit the biological activity. Efficient plant operation is achieved without the need for measuring or adjusting DO. 

The requirements for effluent testing are dependent of the environmental authority and are stated in the approval documents. It is often a requirement to periodically test the effluent for biological oxygen demand (BOD), suspended solids (SS), nutrients such as ammonia, nitrogen, phosphorous and fecal coliform. BIODISK Corporation recommends that both the influent and effluent be tested during the start up period and until the owner/operator becomes comfortable with the process. An experienced eye can visually determine effluent quality by the colour, texture and quantity of the biomass on the disks.


Long Term Biosolids (Sludge) Storage: The ability to have static and long term biosolids storage is both an advantage and a necessity. Biosolids are a source of heat and food with 90% of what is consumed going off in the form of heat. Aerobic biological activity needs DO levels of at least 2.5 mg/L in the wastewater. The BIODISK can have as much as 8 mg/L of DO in the last stage of the process and some of this liquid is recycled back to the primary clarifier to reduce odours.

Buckets are attached to the outside of the disk bank. When the disks rotate the buckets fill and discharge from the fourth stage to the primary sedimentation tank. This recycle introduces a closed loop flow pattern through the primary and all four stages of the disk system. The static sludge continues to decompose under anaerobic conditions.


Anaerobic conditions need DO levels approaching zero. The decomposition of sludge releases dissolved organics and gasses. The anaerobic gases are absorbed into the aerobic layer caused by the high DO in the recycle. The food or dissolved organic matter is transported by the closed loop recycle to the disks. The continuous source of food ensures a stable biological population on the disks. The BIODISK process is not affected by intermittent loadings or seasonal flow changes. The volume of sludge is reduced through aerobic and anaerobic activity. Aerobic activity is quicker than anaerobic activity. The recycle of high levels of DO starts the biological process in the primary tank and reduces biosolids accumulation. Research has shown that the RBC process can reduce biosolids by up to 80%.

The BIODISK does not require the artificial increase in biological population. The bug population does not have to operate in the endogenous phase of respiration. What this means is that the bug population does not have to be operated in a declining growth phase so that they are under fed and hungry. In some treatment plants the final tank influent strength can be 2,250 mg/L. In the BIODISK the final tank influent strength is about 40 mg/L. This low level of final tank influent greatly reduces the potential for excessively high organic wash out. Final tank sludge storage is reduced in volume and strength in the BIODISK. When tertiary treatment is required the biosolids are returned to the primary tank.


No Odour: The RBC process consumes odour. Henry’s Law of Equalized Pressure states that if we put a gas in the headspace of a test tube and clean water in the bottom half of the test tube, the gas will migrate freely from the headspace to the liquid. In the BIODISK the wastewater in the first stage can emit odour. As the process takes effect, the lag stages have greatly reduced substrate strength and subsequently absorb gases and consume odour. Municipal treatment plants and fish feed producers have used the RBC as an odour control device.


In some wastewater treatment processes the strength of the wastewater in the aeration chamber is increased by 10 times. Normal wastewater has a strength of 225 mg/L for biological oxygen demand (BOD). In a suspended growth system the aeration chamber wastewater strength can be 2,250 mg/L BOD. The odour is associated with waste strength. As indicated above, the BIODISK will consume any odour that is given off by higher strength stages. Surplus oxygen levels also reduce odour levels.

Within the BIODISK there is an organic scent to the air. There are no exposed anaerobic conditions or requirements for high levels of BOD. No air is pumped through the system.


Naturally Occurring Microbes: There is nothing to add to the BIODISK process except a small amount of electrical energy. Mother Nature provides all that is required for efficient biological activity.


When in the disk sections, the microbes attach themselves to the disk media. With the rotation of the disks they receive the ingredient they require for their propagation. That ingredient is oxygen.


The disks are 40% submerged in the wastewater and have 60% exposure to the air. As the disks rotate the huge wetted surface area allows the oxygen to enter the wastewater and come in contact with the biomass. Simply put - the bugs breath when out of the wastewater and consume pollutants when in the wastewater. The disks revolve 3 times per minute.


The biological population is segregated. There are thousands of different bacteria that are present in the wastewater. They do not all like to live together. These microbes can be divided into two basic classes. Carbonaceous consuming microbes, bugs that eat organic material, occupy the first stages of the disk. Nitrification bacteria occupy the later stages. These microbes convert ammonia into nitrate.


The carbonaceous microbes consume all forms of organic material and prevent the nitrification microbes from getting established until the wastewater strength is less then 30 mg/L. When the strength of the wastewater is reduced to 30 mg/L there is still sufficient nitrification bacteria to establish a beneficial biomass. These bugs can be referred to as pit bulls and poodles. The pit bull is aggressive and eats everything. The poodle is smaller, not as forceful, harder to maintain and more selective in what it consumes.

The fourth stage process in the BIODISK allows different microbes to dominate in different stages. The different populations can be seen as having different textures, colour and thickness of growth. The BOD removal sections are typically dark brown and have a biomass thickness of 1/16 of an inch. The nitrification section is lighter in colour and has a much thinner biomass. An operator can look at the colour and texture of the disks and know if the plant is operating correctly.


Operator Skill Requirements: The BIODISK is a self-regulating process that looks after itself. The operator requirements are limited to preventative maintenance. The factory has permanently lubricated the drive system. The operator only has to grease the bearings twice a year and take down a few operator notes. When the biosolids accumulation exceeds requirements, the recycle begins to pick up excessive organic content. The disk colour and texture will reveal to the operator when it is time to remove biosolids. Septic haulers remove the biosolids.


The second measure of biosolids accumulation is the sludge blanket. Wastewater contains fats, oils and greases (FOG). This material will float on the surface of the primary tank. Scum accumulation (FOG) is related to the biosolids on the bottom of the primary tank. Visual inspection of the scum blanket will tell the owner/operator when it is time to remove scum and biosolids.


No tests are required to be performed. The operator does not have to determine mixed liquor suspended solids, sludge return rates, dissolved oxygen levels or sludge age. The operator only has to see if the disks are rotating and that the colour and texture of the biomass is normal.
 

Operator Intervention: Operator intervention is limited to preventative maintenance and periodic sludge withdrawal. Normal operations include greasing the bearings, filling any chemical tanks if required for the process, checking the disinfection device and making sure the disks are rotating.

If visual inspection indicates that the biosolids need to be removed the operator contacts a pump out truck. Biosolids from the BIODISK are considered to be primary solids and must be disposed of in a suitable and safe manner.