About ten years ago, the first full scale Biocarbone aerated filter went into service in Soissons (France) for a capacity of 40 000 population equivalents. This compact wastewater treatment system combines aerobic biodegradation and filtration in one unit, eliminating the need for clarifiers and achieving high removal rates through fixed biomass. Since, a number of independent investigations have been performed to establish dimensioning criteria and process performance. This article summarises the reports of the US EPA, the Japanese JSWA, and the British WRC, as well as experiences acquired by cities and water authorities. In pilot and demonstration scale, reactor kinetics, sludge production and energy consumption was measured. Most reports agree on removal rates up to 4 kg BOD/m3 d or nitrification rates around 0.6 kg N/m3 d. Sludge yields ranged consistently around 0.8 kg SS / kg BOD removed, but oxygen transfer measurements varied from 7 % to 15 %. Full scale experience confirms these values, and operation results from large plants in North America are given. Several examples of using the Biocarbone process for low pollution residuals are demonstrated, including plants in Britain, Denmark and Switzerland. As tertiary installation fed with clarified secondary effluent, final residuals below 1 mg/l N-NH4 and 5 mg/l for SS and BOD can be achieved in a hydraulic detention time around one hour. On settled sewage, two hours detention time results in advanced secondary effluent quality below 5 mg/l N-NH4 and around 10 mg/l for BOD and SS. If an anoxic reactor is added, total nitrogen residuals below 10 mg/l can be achieved in about three and a half hours.
Biological reactors using a culture fixed on a fluidized bed are suitable for many applications in waste water treatment. A large number of studies have been carried out at the pilot-plant scale but none exists at the industrial scale for municipal waste water treatment. Examples are: - Dorr Oliver (Sutton + Mishra) (1) - The Biolex process developed by EBARA (2) - The reactor described by Heijnen (Holland) (3) In the latter two processes, fluidization and aeration are provided by an air-lift system inside the reactor. This article describes the Biolift process whose original feature is that the air-lift system is outside the reactor and is assisted by a system to inject secondary air (process air) into the reactor. This combination allows tight control of fluidization and aeration factors.
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Experience with biofilters, acquired over many years, has made it possible to control their operating parameters. The goal of this article is to present an assessment of operational biofilters, in particular their air consumptions, their sludge productions, their energy balances as well as the duration of their filtration cycles. Some tests, carried out on medium to large full scale units, are described at the same time as the process results. These experiences in the design and operation of biofilters led to their optimization and make it possible to build very large scale installations. Examples of such plants, now being built or started up, are also presented, treating flows in excess of 50 000 m3/d even for low nitrogen residuals.
Stringent effluent quality programs to limit wastewater discharges into receiving waters require extensive upgrading of conventional wastewater treatment plants. Large facilities built some decades ago are now often located in densely urbanised areas where land is unavailable. Since nitrogen and phophorus removal often require additional unit processes, innovative solutions have to be found to upgrade existing plants for nutrient removal. This paper shows large scale examples of compact technology and the additional upgrading flexibility provided. New facilities are implemented in sensitive neighborhoods by creative siting under sports stadiums, parks or buildings. In covered plants, air emission control becomes of primary importance. To reduce visual impacts and facilitate odour control, more and more underground treatment plants are constructed, allowing multiple use of plant surfaces. Several plants are illustrated in inner-city locations, avoiding infrastructure cost to pump sewage to remote sites. Most of the presented plants incorporate spacesaving settling facilities and high rate biological reactors to reduce the ‘footprints' of the installations and thus favour coverage. Parallel plates in primary setllers reduce the surface to about one tenth of conventional systems. Biocarbone aerated filters combine biodegradation with very high removal rates and retention of particles in one reactor, without additional clarification or filtration. Air treatment for large plant is mostly performed by chemical scrubbing, completely eliminating environmental nuisances. Performance results of both air and water treatment technology are given. Examples include recent sewage treatment plants on the French Mediterranean Coast. A physico-chemical treatment plant for 1 Million p.e. has operated since 1987 under a stadium in Marseille. In Monaco, the sewage treatment plant for 100 000 p.e.is located in the city center underneath a building of 3000 m2. Primary lamella settlers are followed by biological treatment on Biocarbone aerated filters and air is chemically deodourised. Similar technology is used in Antibes' 200 000 p.e. plant, integrated underneath a park close to the beach.
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