【正文】 l land, recharge of aquifers or river flow replenishment. On several occasions this was the major decision criteria to opt for MBR technology. With the choice of the MBR special attention should be paid to the fact that the investment costs are largely correlated with the hydraulic peak flow. This parameter determines the total membrane surface area which needs to be installed. Therefore, acpanying measures to minimize wet weather flow or to harmonise resultant wastewater largely contribute to cost effectiveness of the MBR approach. One option for dealing with high wet weather peaks is to use the former secondary clarifier as storage volume. Another option is hybrid systems where the conventional system is used as a backup to treat the inflow volume that exceeds the hydraulic membrane capacity. An already realised hybrid concept designs the MBR line to treat the dry weather flow at the maximum. The inflow volume beyond dry weather conditions is treated conventionally.3. Modification of the operation mode using the MBR approach With the change of sludge/treated wastewater separation from gravity settling to membrane filtration the following process configurations are available:. MBR with or without a separate filtration chamber With upgrading of wwtp as a pure MBR process the question is to be cleared whether existing sedimentation tanks can be included sensibly in the future concept of utilisation. According to the structural state it can be possible to use thestanks as an additional biological volume. Also the suitable installation and operation of the membrane modules either in activated sludge tanks or in separated filtration chambers depends on the quality of the respective structural situation. At this point wide engineering space is given. Fig. 1shows some possible variations.. Hybrid systems The bination of the CAS process and the MBR process is understood as the hybrid procedure. Fig. 2 shows two basic operation concepts of hybrid processes (among other hybrid systems). Besides, a fullness of mixing variations is possible. The flow concept of the sludge streams between both biological units at parallel operation mode or serial operation mode can be operated separately or bined according to the local circumstances (grey arrows in Fig. 2). In the latter case possible differences are to be taken into consideration concerning the sludge qualities, in particular, the quality of sedimentation and the MLSS concentrations.. Other processes Beside the bination with the CAS process also binations with other wastewater treatment procedures are possible, . with SBR technology [1] or with pond technology. Today SBR technology integrating membrane technology as separation process is used at industrial applications or at package plants. Applications bining pond technology and MBR technology are operated at wwtp St. Peter ob Judenburg, Austria and at wwtp Ihn, Germany.. MBR process with low MLSS concentration In cases when available sedimentation volume is used as additional biological volume, the amount of total biological volume increases to a degree, that clearly exceeds the usual volume demand of a conventional MBR process with appropriate MLSS concentrations ranging from10kg/m179。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