More than fifty wastewater treatment plants worldwide (representing several millions p.e) are equipped with up-flow biofiltration reactors (BioforR). Their range of application encompasses municipal as well as industrial wastewater. A summary of the results achieved in a large number of plants is presented, accompanied by a description of the operating parameters and the treatment limitations with regard to various pollutants (C, N, P). The separation of functions into specific reactors combined with optimized wash conditions guarantees high treatment efficiency.
In order to investigate the upper limit of aerated biofilm processes, a series of experiments has been carried out on a pilot scale with a synthetic effluent containing only ammonium nitrogen and inorganic carbon as substrates. The influence of water velocity, air velocity and media height has been studied without the interaction of organic carbon and suspended solids. Under these conditions, the increase of the hydraulic load has a positive effect on the maximum nitrified load, despite the shortening of contact time. The pilot plant was able to nitrify 2.7 kg NH4+-N/m3.d at 14° C with an empty bed hydraulic retention time as short as 6 minutes - under a 30 m3/m2.h hydraulic load. It was also demonstrated that a cubic meter of granular bed presents the same nitrification capacity in a 3 m or in a 4 m media high biofilter, only if placed under the same conditions of air and water velocities. The results confirmed that water velocity significantly improves substrate bulk/biofilm transfer, and demonstrated that neither a contact time - based on the pore volume - as short as 2 minutes nor a media height of 4 m limit the nitrification rate.
A one-year study was carried out on two semi-industrial submerged up-flow biofilters - a pre-denitrification (pre-DN) step followed by a nitrifying (N) step, designed to treat the primary settled municipal wastewater of a full scale plant for both carbon and nitrogen removal. Performances of the pre-DN step have been investigated showing high removal denitrifying capacities – 1 to 1.2 kg NO3−–N removed per m3 of reactor per day–, obtained with high TSS and carbon loading rates, at a water velocity up to 21.5 m3/ m2.h. The complete treatment plant – primary settlement + pre-DN/N loop – has demonstrated a nitrogen removal efficiency ranging from 70% without any additional carbon, up to 85% with methanol. COD and TSS removal rates were 91% and 97% respectively. The above results show that two submerged biofilters in series form a treatment line suitable for nitrogen removal. This technical choice leads to very compact full scale plants such as Ahlen WWTP (Germany, 85 000 PE).
An understanding of the waste water nature, from both the qualitative and quantitative points of view, is a fundamental factor in the selection of treatment techniques and their subsequent operation. This is even more so in the case of small communities whose discharges are more subject to variation. An analysis of French data in this field provides values for small communities in rural areas (the majority). So far as other communities are concerned there are three examples which particularly illustrate the effects of the different factors (way of life…) on specific loads.
SUMMARY compact facilities together with modular and environment-friendly appearance are arguments in favour of Biological Aerated Filters(B. A. F. ) in coastal areas where the amount of available land imposes strict limitations on technological choices. The operation of B. A. F. in combination with a physico-chemical process was studied using the data obtained from two wastewater treatment plants located in coastal areas (Barcares and Saint Palais/Mer, France). The main conclusions are the following.-Effluent quality in terms of COD, BOD5 S.S. proved satisfactory for organic load conditions higher than those applied when using conventional procedures.-Adaptation to organic load variations is not a basic problem for this type of coastal community,but hydraulic flow-rate control should be the main concern.-Restarting plant operation after a long shutdown only takes a few days.-Furthermore technical and economical optimisation required continuous monitoring, especially in the field of washing and aerating control. This type of management involves the use of reliable, high- performance control equipment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.