【正文】 ght can be realised, the usual disadvantages (sensibility pared to impact load, reduced alpha value) could be overe by MBR process to a great extent. Beside the anyway raised effluent quality other advantages of this upgrading concept can be named:considerable biological reserve capacities for future extension。smaller place consumption pared to a conventional upgrading concept.Some manufacturers of membrane modules remend not falling short of a given MLSS concentration directly at the membrane or within a separated filtration chamber. Thus, the suitability of the respective membrane modules for the “l(fā)ow MLSS operation mode” is to be , by the construction of a separate filtration chamber optimal MLSS concentrations at the membrane and within the biological zone can be adapted accordingly.. MBR in bination with anaerobic sludge stabilizationUp to now most municipal MBR plants are dimensioned with aerobic simultaneous sludge tabilization. In principle the MBR process also can be bined with anaerobic sludge stabilization. Some single studies assume dependence between increasing fouling potential and increasing F/Mratio or rather decreasing SRT [4–6]. A final statement cannot be met yet. If the MBR process is dimensioned with a short SRT, hence, possible intensified fouling effects have to be considered. If the MBR process is dimensioned with a long SRT, slightly reduced digester gas production can be expected. A possible process variation features the digestion of only primary sludge. Thus, in an upgrading situation the cost intensive new building of digestion volume can be avoided.4. Experiences from fullscale applicationsThe full version of DWA WG report includes all subsequently mentioned wwtps:?wwtp St. Peter ob Judenburg, Austria?wwtp Schilde, Belgium?wwtp Eitorf, Germany?wwtp BergheimGlessen, Germany?wwtp Brescia, Italy?wwtp Viareggio, Italy?wwtp Heenvliet, Netherlands?wwtp Rietliau, Switzerland Upgrading of wwtps by means of MBR technology is not a question of special membrane types. The above mentioned plants are equipped with usual and well known hollow fibre membranes as well as with flat sheet membranes. In the following two plants out of the above mentioned are now introduced more , the German wwtp BergheimGlessen is an example for a plete process rearrangement. The Swiss wwtp Rietliau shows a hybrid solution.. wwtp BergheimGlessen, Germany In the case of the wwtp BergheimGlessen MBR technology is used to meet advanced requirements caused by the discharge of wastewater to sensitive wetland. Upgrading occurs at the existing location using extensively already existing constructions. Treatment efficiency will be rapidly increased by introducing MBR technology. Hence, in addition, the wastewater of aneighbouring, smaller wwtp, likewise in the need of upgrading, is led across, treated and afterwards led back. Thus, the wwtp load is raised from 5,. nowadays to 9,000 . Wastewater quantity to be treated from now on amounts to 900,000 m179。/a. Fig. 3 illustrates the flow diagram.The mechanical pretreatment is pletely renewed consisting of three units: screening (gap size 6 mm), aerated grit chamber and grease trap,sieving (mesh geometry, gap size 1 mm). The existing oxidation ditch furthermore will be used as activated sludge volume. SRT should amount about 25 d, MLSS concentration is dimensioned with only 8 kg/m179。. In time of maximum inflow HRT amounts to 6 h. The membrane modules are installed in four separated filtration chambers. Sludge treatment and simultaneousprecipitation are taken over from the today’s continuance. The plant is scheduled to be missioned in late 2007.. wwtp Rietliau, Switzerland Upgrading was necessary to meet the effluent requirements (DOC: 10 mg/l, BOD: 10 mg/l, P total: mg/l, SS: 5 mg/l) especially according parameter SS which was unachievable by the former wwtp concept. An upgrading of the treatment capacity from 41,400 . up to 44,000 would have been acplished by depth filtration as a fourth treatment step. Caused by small space availability the hybrid solution was evaluated as an economically more favourable of space is due to the wwtp location in the midst of the residential area W228。denswil, 100m far from the bank of the Lake of Zurich. Fig. 4shows the flow diagram. Wwtp Rietliau was missioned in November 2005. The treatment process is subdivided into two lines. Each, the MBR line and the conventional process line, treat half of the ining Wastewater. Sludge of both treatment lines is not mixed. All wastewater is treated by the existing mechanical pretreatment units (screen, grit chamber and grease trap, ）. In addition, the inflow from the primary sedimentation to the MBR line is led through a sieve consisting of hole geometry with 1 mm gap size. The MBR line consists of two sublines. Aerobic and anoxic volumes of the MBR process are dimensioned the way, that in times of maximum inflow the minimum HRT within the biological zone prior to the filtration chambers does not fall below 30min. Better effluent quality concerning the conventional process line also is achieved caused by the less hydraulic load of the secondary clarifiers. Thus, the requirements that have to be met by the mixture of both effluent streams can be guaranteed.5. ConclusionsThe presented upgrading concepts raise no claim to pleteness and thus reveal the wide spectrum of supposable measures. Many of them are under investigation and appropriate findings can be expected to be reported soon. However, the chosen upgrading concept must meet the claim to be?demandoriented according the wastewater sided requirements and the load situation,?economical in view of annual costs (operating expenses and net debt service). Besides, various other, not only processrelated, but also nonmonetary and monetary hardly assessable aspects are to be followed and to weigh in each individual case which do not admit a standa