Energy input and sludge production are very low compared to conventional treatment plants, due to the anaerobic conversion of the major part of the biological matter. Further benefit is the elimination of odour since the anaerobic compartment is fully closed and first stage effluent is directly routed into the upper aerobic stage. The absence of a secondary settling tank eliminates the hazard of mosquito breeding.
This technology is applicable as sewage treatment in (sub)tropical climates, but also finds its way in industrial applications.
Capacities are in the range of 5,000 to 100,000 p.e.
This technology has already been proven at several full-scale plants, both in the municipal and industrial field.
- Small footprint, compact construction
- No moving parts
- Low energy consumption for aeration of the residual biodegradable matter
- Possibility of energy reuse from biogas production
- Low sludge production
- No odour emissions
- Low maintenance requirements
The BIOPAQ®UBOX bioreactor has two sections: an anaerobic lower section and an aerobic upper section. The wastewater is pre-treated anaerobically, using anaerobic sludge in the bottom part. Biogas is produced and separated in the three phase proprietary separators. The separator modules also effectively keep the anaerobic sludge in the lower part of the reactor.
In the upper part of the reactor air is introduced to enhance aerobic degradation of the residual COD. An efficient separator in the upper part of the tank allows for the discharge of settled effluent while keeping the activated sludge within the reactor, at the same time avoiding air bubbles to interfere with the settling process.
In anaerobic treatment, bacteria convert organic compounds (COD) to biogas in an environment without oxygen. Not only do the bacteria remove contaminating compounds from the effluent, thereby reducing discharge costs, they produce green energy at the same time.
Organic components (COD) are converted to CH4 + CO2 + BIOMASS
The generation of biogas from agricultural waste, municipal slurries and wastewater has been gaining interest from scientists, industry and municipalities interest is rapidly growing now, since renewable energy sources are favoured to limit global warming. Biogas consists mainly of methane and some carbon dioxide. It can be utilized as a fuel for power generation, steam production and drying processes.
Paques started the design and supply of installations for COD conversion into biogas in the early nineteen eighties with the application of the BIOPAQ®UASB (Upflow Anaerobic Sludge Blanket) reactor. This was an invention of Professor Gatze Lettinga from Wageningen Agricultural University in the Netherlands. The reactor was scaled up from pilot to full scale and deployed for many types of wastewater.
Paques quickly became global market leader in this field of anaerobic treatment. Its position was further strengthened by the development of a new type of anaerobic reactor called the BIOPAQ®IC (Internal Circulation) reactor. Both the BIOPAQ®UASB reactor and the BIOPAQ®IC reactor are used for wastewater treatment with a wide range of carbohydrate concentrations, i.e. from 1,000 to 20,000 mg COD/l.
Within this range the bacteria form compact granules with very good settling characteristics. Above this range the bacteria tend to grow in a more flocky structure and for this Paques developed the BIOPAQ®UASB+ reactor. For more concentrated wastewaters containing fine organic particles and/or fat and proteins, Paques designed the BIOPAQ®AFR (Anaerobic Flotation Reactor).
For decentralised sewage treatment in warmer climates, Paques has developed the very compact BIOPAQ®UBOX, which combines a first stage anaerobic treatment with a second stage aerobic treatment.
Paques’ reactors are found in all kind of industries and applications, such as Food, Pulp and Paper, Beer and Beverages, Distilleries and Chemical and Pharmaceutical.
In an aerobic treatment system, air is injected which is used by aerobic bacteria to convert BOD to carbon dioxide and water.
Organic components + O2 are converted to H2O + CO2 + BIOMASS
Primary treatment for solids removal and anaerobic treatment are usually followed by aerobic treatment.
Paques offers different solutions the aerobic post treatment, such as
- Activated sludge for surface water discharge quality
- Flash aeration for oxidation of odorous compounds
- CIRCOX® airlift technology for situations with a very limited space available
- BIOPAQ®UBOX for the compact combination of anaerobic and aerobic treatment
Activated sludge system
The activated sludge system consists of an aeration stage - and an anoxic/oxic compartment if nitrogen has to be removed - and secondary sedimentation with sludge return. Options are first quality surface aeration, fine bubble aeration and jet aeration.
After secondary clarification, further treatment can consist of filtration, de-nitrification (for achieving very low nitrogen concentrations) or effluent softening. For nitrogen removal at higher concentrations and filtration, see ANAMMOX® and ASTRASAND®.
When treated water will be reused or if water will pass through a sewer, flash aeration is often required. The main reason is odour control, but it will also remove some additional COD, especially when the aeration tank is followed by solids removal such as DAF (Dissolved Air Flotation).