英语论文一篇 求翻译!!!

Comparison of startup and anaerobic wastewater treatment in UASB, hybrid and baffled reactor

Abstract
An experimental study was carried out to compare the performance of selected anaerobic high rate reactors operated simultaneously at 37 °C. The three reactors,namely up¯ow anaerobic sludge bed reactor (UASB), hybrid of UASB reactor and anaerobic ®lter (anaerobic hybrid reactor ± AHR) and anaerobic baf¯ed
reactor (ABR), were inoculated with the anaerobic digested sludge from municipal wastewater treatment plant and tested with synthetic wastewater. This wastewater contained sodium acetate and glucose with balanced nutrients and trace elements (COD 6000 mg á l)1). Organic loading rate (Bv) was increased gradually from an initial 0.5 kg á m)3 á d)1 to 15 kg á m)3 á d)1 in all the reactors. From the comparison of the reactors’ performance,the lowest biomass wash-out resulted from ABR.In the UASB, signi®cant biomass wash-out was observed at the Bv 6 kg á m)3 á d)1, and in the AHR at the Bv 12 kg á m)3 á d)1. The demand of sodium bicarbonate for pH maintenance in ABR was two times higher as for UASB and AHR. The ef®ciency of COD removal was comparable for all three reactors ± 80±90%. A faster biomass granulation was observed in the ABR than in the other two reactors. This fact is explained by the kinetic selection of ®lamentous bacteria of the Methanotrix sp.under a high (over 1.5 g á l)1) acetate concentration.

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Introduction
Up¯ow Anaerobic Sludge Bed (UASB) reactor, Anaerobic Hybrid Reactor (AHR) and Anaerobic Baf¯ed Reactor (ABR) belong to the group of high-rate anaerobic reactors with a sludge bed. Granular biomass with high methanogenic activity and excellent settling properties can be cultivated in these reactors. The UASB reactor (in sequel as UASBR) consists of a sludge bed in the lower part and a three phase separator (g-l-s separator) in the upper part of the reactor [1]. The AHR is a combination of the UASBR and the anaerobic ®lter [2]. A layer of biomass carrier is situated in the upper part of the AHR instead of the g-l-s
separator. This layer separates the bubbles of the biogas from the biomass and acts as a support material for the biomass growth as well. The layer even has a notable ef- ®ciency as a suspended solids (SS) separator [3]. The ABR (®rst described by Bachmann [4]) contains a mixed culture of anaerobic microorganisms which is divided into compartments by baf¯es (mostly vertical baf¯es are used).A sequence of sludge blanket reactors is created in this simple way. An ABR performed in a propriet mode allows high hydraulic loadings connected with low biomass washout [4, 5]. The general principles of the anaerobic sludge
granulation were described by Hulshoff Pol [6].

In our previous works, we dealt with the performance of the above mentioned reactors one by one [3, 5, 7]. Even if there were some differences in the substrates used as a feed for these reactors, the similarity of them was high enough to make possible the comparison of the reactors performance (treatment ef®ciency, biomass wash-out,biomass granulation). In all of the cases, the substrate consisted of saccharides with lower molecular weight (glucose and sucrose) and the Volatile Fatty Acids (VFA),total COD was 4000±6000 mg á l)1.

Hence this work is dedicated to a detailed comparison of the performance of three different types of anaerobic high rate reactors performed under the same conditions with the same feed.