Oldcastle Precast® Decentralized Wastewater Systems
patented Algaewheel® technology
Frequently Asked Questions
AlgaePac - FREQUENTLY ASKED QUESTIONS 2/14/11 sjk
Q: Is the algae necessary for AlgaePac to meet discharge limits?
A: AlgaePac uses bacteria and algae to treat wastewater. The algae does not replace the
bacteria, it makes the system more efficient. One could cover the wheel modules preventing
the growth of algae and the system would still meet regulatory discharge limits by the
conventional bacteria-based, attached-growth process. Some of the key benefits of using algae in the treatment process are reduced energy requirements, greenhouse gas abatement and capture, and simple system design. In addition, algae biomass may be used for production of biofuels or fertilizer.
Q: How long does it take for the algae to grow and for the system to start meeting limits?
A: Startup times vary but typically two weeks to start meeting limits and four to six weeks for full
Q: What is the cost of the AlgaePac system?
A: The cost of an AlgaePac system is project and application dependent but is comparable to a
conventional activated sludge system.
Q: How many wheels do I need?
A: For municipal waste applications, one algaewheel treats between 55 and 83 gpd. For example, a 40,000 GPD plant would have approximately 540 algaewheels.
Q: How big is an AlgaePac system?
A: AlgaePac has a relatively small footprint. A 7000 GPD system is approximately 30’x35’ and a 45,000 GPD system is approximately 65’x65’. In addition, the modular design allows systems to be configured to best fit the site layout.
Q: Is this just another RBC?
A: No. First of all, the wheels are much smaller (<20” in diameter). Second, the wheels are not driven by complicated and high-maintenance chain drives - they wheels are driven by air bubbles from low-energy regenerative blowers. Lastly, the wheels are exposed to sunlight and are used to grow and automatically harvest algal and bacterial biomass (we call it an RAC for Rotating Algal Contactor).
Q: How does the system scale up?
A: The AlgaePac system is modular. The system is designed to be scaled to any capacity simply
by adding additional modules.
Q: What percentages of BOD and TSS will the primary clarifiers typically remove?
A: Typically 30% BOD and 70% TSS, but this may vary for each system.
Q: Will the algae remove organics?
A: No. Algae remove inorganics like nitrogen and phosphorous. Bacteria in the AlgaePac system will process organics.
Q: How much algae does your system produce?
A: The AlgaePac system will produce approximately 2-3 Lbs biomass for every pound of influent BOD.
Q: Is the algae you produce a specific species?
A: We do not attempt to inoculate or control the species of algae. We allow the algae to establish in
the system naturally. There are generally many different types of bacteria and algae in our
Q: Will an AlgaePac system treat my industrial process wastewater?
A: If the wastewater can be treated with bacteria, then yes. A pilot system will be required to
determine operating parameters and costs.
Q: Can the AlgaePac system treat agricultural wastewater?
A: Yes. A pilot system will be required to determine operating parameters and costs.
Q: Does the AlgaePac system replace a conventional wastewater treatment plant?
A: Yes or No. The AlgaePac system can be a stand-alone packaged treatment system, or it can be used to provide additional treatment for existing systems.
Q: Is AlgaePac approved by regulatory agencies for wastewater treatment?
A: Yes. AlgaePac is formally approved by several state agencies. In addition, since AlgaePac is a tertiary treatment system (surface discharge as allowed by local regulations) many states do not have a formal pre-approval process for wastewater technologies. Their approval is on a project by project basis.
Q: Does the AlgaePac system smell?
A: No. The entire algaewheel process is aerobic so no odorous gases are produced.
Q: Can the AlgaePac system be used for nitrogen and phosphorous removal?
A: Yes. Algae utilize both nitrogen and phosphorous to grow.
Q: Will the algae remove heavy metals?
A: Yes. Algae are extremely efficient at heavy metals removal. However, this may cause issues in
the downstream processing of the algae. Typical municipal wastewater will not create a metals
problem with the algae. However, some industrial processes and metals machining operations
may create problems if there is no pre-treatment required by the municipality.
Q: Can algae grow year round in northern climates?
A: Yes. In northern climates, the AlgaePac wheel tanks are installed with low-profile greenhouse covers or in a greenhouse to provide optimum growing temperatures year round.
Q: Does ferric/ferrous chloride for phosphorous removal affect the algaewheels?
A: Iron is actually beneficial and enhances the growth of algae significantly.
Q: How does varying influent flow and loadings affect the algaewheels?
A: The algaewheel process is an attached growth process so it can handle varying flows and loadings very well. The system can handle a hydraulic peaking factor of 4:1. Anything above that
would require flow equalization.
Q: Does temperature affect algae?
A: Yes. The temperature must be maintained between 45-100 degrees Fahrenheit, similar to other treatment systems. In northern climates, the algaewheels are installed with greenhouse covers or in a greenhouse to provide optimum growing temperatures year round. Ventilation is provided to reduce temperatures in the summer.
Q: How do you protect against freezing in the winter?
A: In northern climates, the algaewheels are installed with greenhouse covers or in a greenhouse to prevent freezing.
Q: What can harm algae?
A: There are chemicals, such as copper sulfate, that can kill algae and are used to keep lakes and reservoirs clear of algae. However, algae are very resilient organisms and quick to recover. It is
highly unlikely that typical municipal wastewater would contain toxins at the levels required to kill
algae. In fact, most wastewater treatment plants can’t keep algae from growing in their clarifier tanks
which is one of their biggest maintenance headaches.
Q: Can supplemental CO2 be added to the AlgaePac system to enhance algal growth?
A: Yes. Air blowers deliver air through an air distribution grid system located below the algaewheels to
rotate the wheels. CO2 can be directed into the intake of the blowers for even distribution of the
CO2 throughout the entire algaewheel system.
Q: Does the algae uptake CO2 at night?
A: No. The algae will respire at night.
Q: How is the algae collected in the AlgaePac system?
A: The algae and bacteria are collected using conventional clarifiers. The combination of algae and
bacteria settle far more efficiently than bacteria or algae independently. The algae/bacteria
biomass coagulate better, cohere better and are freely drainable so that they can be dewatered
and dried much more efficiently if not digested in a central digester tank.
Q: What are options for processing the algae biomass once it is collected?
A: The collected algae biomass can be digested in a conventional digester tank as part of the AlgaePac system. For larger scale system, another option includes dewatering with a conventional centrifuge, belt press, or other system and drying utilizing solar drying or mechanical thermal drying processes. After that, the algae biomass can be either sold or thermally processed to produce energy. Thermal processes include pyrolysis, gasification, and combustion. The thermal value of the algae biomass is about 10,000 BTU/lb Anaerobic digesters can also be used to process the algae biomass into bio-gas.
Q: What are the effluent discharge options?
A: Depending on local regulations, AlgaePac will treat waste to surface, subsurface, or reuse discharge quality.
Q: Why don’t you make the wheel bigger?
A: We have constructed multiple sized wheels including 2-ft, 4-ft, and 8-ft diameter wheels. The wheels were operated side by side for several years and it was concluded that the smaller wheels
were more efficient at treating wastewater than the larger wheels. In addition, the smaller wheels
eliminated the structural and maintenance problems associated with larger heavy wheels. Lastly, the smaller wheels are much easier to mass produce significantly reducing cost.
Q: Why hasn’t anyone done this before? It sounds too good to be true.
A: It may appear that way but the answer is actually very simple. When bacteria based wastewater
treatment processes were developed, energy was inexpensive and there was no concern about
climate change. Clean water, clean air, and clean energy are now the biggest challenges facing
Q: Who can I buy a system from?
A: AlgaePac packaged wastewater systems are available exclusively from Oldcastle Precast. Please call us at 888-965-3227. Municipal wastewater treatment plants are available from Algaewheel LLC.
Q: What are the maintenance requirements? What are the wheels made of? How long do the
wheels last? How are the wheels accessed?
A: The algaewheels are 100% plastic, buoyant in water, UV protected and designed to operate for
over 20 years with no maintenance. In the unlikely event the algaewheels need to be accessed, removable end panels are provided in the greenhouse covers.