Bennett Environmental – Integrated Anaerobic and Aerobic Treatment
Bringing Aquanos Technology to U.S. Dairy
Aquanos was founded in Israel in 2011 by an experienced team of accomplished industry professionals in the biogas, water, and wastewater markets. This technology was one of the winners of an Israeli national program to find economic solutions for the dairy industry’s wastewater treatment needs. Aquanos has established 25 systems in Israel and submitted patent applications in the US, EU, China and India.
The system has two phases. The first phase is anaerobic digestion using a high rate UASB reactor that produces biogas for conversion to RNG or electricity. The second phase is aerobic digestion using algae raceways to provide oxygen to aerobic bacteria that further reduce COD and allow for denitrification.
Bennett Environmental has secured licenses for bringing this Israeli technology to the United States.
Waste is screened and degritted before being introduced into an anaerobic stage, a fully engineered Upflow Anaerobic Sludge Blanket (UASB) reactor. This stage is meant to produce high methane content biogas and reduce organic loading, as well as serve as a sink for excess algal and bacterial biomass.
Following the anaerobic stage, the wastewater is introduced into a Moving Bed Biofilm Reactor (MBBR) where aerobic COD removal and nitrification take place. In the process, the active biomass is grown as a biofilm on small, cylindrical HDPE elements of about 10 mm X 10 mm, designed to maximize protected surface area and mass transfer of substrates and oxygen from the bulk liquid into the biofilm. Unlike activated sludge, the biomass carriers (with the active biomass) are retained within the reactor by sieves, and only excess biomass, shorn off the biomass carriers, is carried over to the final solids-separation system (clarifier, dissolved air flotation unit, or filter) with the effluent. The use of an attached growth system, where the biomass is confined physically to one unit and does not flow through the system, allows the oxygen-rich algal liquid to flow through the system with minimal mixing of algae and bacterial mass; this in turn minimizes contamination of the algal raceway with bacterial biomass, flocs, etc, thereby improving environmental conditions for the algae.
Oxygen to the MBBR is supplied by algae-rich water residing in open raceway reactors. The area, number and staging of the raceway reactors will depend on the process characteristics and amount of oxygen required. The oxygen-rich liquid is recirculated to the MBBR utilizing high-flow, low head pumps; from the MBBR the now oxygen-depleted liquid is returned to the raceway to resume photosynthetic oxygen production.
Final effluent is conveyed either from the MBBR or from the raceway to a final solids-separation unit. Depending on the type of application and required effluent quality, this could be anything from a simple clarifier or lagoon to a Dissolved Air Flotation unit. Excess biomass (algal and bacterial) is removed from this stage for further processing, either in the digester, or for production of fertilizer, bioplastics, animal feed, or, in the future, biofuel.
The anaerobic and aerobic segments are sized according to standard design procedures for UASB and MBBR systems, respectively.
Technology Strengths, Weaknesses and Critical Indicators
- Long usable life and can be run reliably
- Creates energy and generates environmental credits
- Proper feeding & system monitoring is required to avoid system downtime
- Proven technology for odor control
- Proven technology for GHG reduction
- Proven technology for pathogen reduction
- Different types of systems produce varying gas production rates
- Requires proper preparation of the feedstock
- Requires other technologies for energy utilization
- Requires other technologies for digestate handling
- Requires other technologies to prevent nitrogen loss
- Complex systems may require expertise not available on-farm
Bennett Environmental has been operating a pilot scale system in California since 2018. The system, operating on a a 1,500 cow dairy with flush manure collection, takes <10% of the manure from after the solids separation system to a digester and algae raceway. This system has documented nitrogen and phosphorous reductions of approximately 90% and 73% respectively.
Newtrient will continue to work with Bennett Environmental to further refine the cost and performance information as more information becomes available and as new commercial dairy installations come on line. The technology has not been given a 9-Point score as it is a pilot system.
1. OPERATIONAL HISTORY