In Quebec, the municipalities must make sure that their rejections of sewerachieve the goals applied to the receiving medium. The Rotating BiologicalReactor (RBR), developed by the biological processes division of H2OInnovation, showed its effectiveness during more than one year testingproject, which contribute to the obtaining of the Standard Technology (CF-1) certification allowed by the Quebec Ministry of Environment and theDepartment of Municipal Affairs http://www.menv.gouv.qc.ca/eau/eaux-usees/usees/reacteur_rbr.htm
Pilot Projet at Saint-Claude (Estrie)
The wastewater treatment station of the municipality of Saint-Claude (Estrie,Quebec) was used as a pilot system for the RBR technology. After a 22month period of operation, the system showed its capacity to meet therequirements of the Quebec Ministry of Environment and the Department ofMunicipal Affairs, the whole activities being controlled by the GovernmentCertified independent laboratory: Biolab Laboratories Inc.
The Rotating Biological Contractor is an improved version of the biodisc, an existing technology formore than 75 years in Europe. H2O Innovation simplified and refined the whole mechanical componentsof the initial system allowing a water purification which shows effective performances and long-termreliability. The innovation is the patented media (bacterial support on which sets the purifiying bacterias).The physical properties of the media limit the formation of biological bridges (filling) between thesupports, that were at the origin of mechanical breakings met during the use of this technology (specificoverload and breaking of the central axel).
The operation of the RBR is connected to the biodiscs (RBC’s). As treatment basis, the biological processuses fixed bacterial growth on a bacterial support. The continuous rotation of the RBR, 55% submergedin used water, allows the oxygen contribution. The slow rotation exposes the biomass fixed on the mediato the ambient air, creating favorable conditions to the growth of the biomass fixed on the support.
Three RBR of a 4 feet diameter (series 1250) were installed in parallel, in order to carry out thebiological treatment. The RBR are preceded by a septic tank (individual or community according tothe project) and a 12 hours flow-regulation tank allowing to manage the strong peak periods. Asecondary settling tank, located at the exit of the RBR, allows the clarification of water treated anda recovery of biological sludge produced. A storage basin of biological sludge supplements the dataprocessing sequence. The supernatants of this basin turn over at the head of the equalization basin.
Management of the Parameters
The output of the system was followed throughout all the demonstration. The principal parameters analyzed are:
- Biochemical demand for oxygen (BOD5)
- Suspended matter (SS)
- Chemical demand for oxygen (COD)
- Fecal coliformes (FC)
- Ammoniacal nitrogen (NH4)
- Hydrogen sulphide (H2S)
During the pilot project, the recorded flows were definitely lower than those initially estimated (15instead of 30m³/d). Consequently, the real loads applied were quite lower than those estimated for thesystems design (1,65 kg BOD5/d in the influent of the RBR and 0,73 kg SS/d). Thus, to evaluate themaximum real loads precisely being able to be supported by the technology, H2O Innovation took theinitiative to stop gradually RBR units at the time of the demonstration. After the first four months ofexploitation, a first RBR unit was stopped (August 1997). As the standards of rejections were alwaysrespected with two units in function, a second unit was put out of service after nine months ofoperation with two RBR (May 1998). The follow-up of the performance then continued with onlyone RBR in function (10 months).
In any time, the standards of rejections for the BOD5 were respected. However, during the winter when only one RBR were functioning, there were some results beyond the standards. On average, the outputs obtained for the removal of the BOD5, during the project are : 90 % of removal for the follow-up period, 86 % of removal for the period with only one RBR, including 92 % in summer period and 71 % in winter period. However, since few analyses were carried out for this last period, it is necessary to pay attention to the hasty conclusions. Concerning SS, the standard of rejections was respected at any time during the follow-up period.
Finally, with only one recovery, the standard of rejections of 200 U.F.C./100mL for the fecal coliformes was slightly exceeded. The standard was however respected for the rest of the follow-up.
Sanction of Technology
After analysis of the results, the Quebec Ministry of Environment and the Department of Municipal Affairs decreed highest classification for a new technology, which is 'standard' certification. Being the first technology with accredited fixed culture, the chart of the RBR carries number CF-1. This certification has many advantages of which to be pre-approval for the requests for certificate authorization and to have an effectiveness shown and tested for the treatment presented in the chart.