From pilot test to large-scale ultrafiltration plant at the drinking water treatment plant Trier; Germany

摘要

The Public Utility Company of Trier has decided to modernize their drinking watersupply be replacing their current coagulation/multimedia filtration system by amodern Ultrafiltration system due to deficits in drinking water quality. The watertreatment system was designed for a capacity of 10 MGD. Main objective was toimprove the quality of purified drinking water, which is obtained out from the reservoirnamed “Riveris”.In the run up to modernisation from March 2008 till July 2009 an extensive 16 monthlasting pilot study has been carried out to verify the performance of several UFmembrane systems with regard to operational stability, reliability, filtrate quality,energy efficiency and chemical consumption. During the pilot test, one pressuredriven out-in microfiltration system equipped with polyvinyldenflouride (PVDF)membranes and three different pressure driven in-out ultrafiltration systems equippedwith polyethersulfone (PES) membranes were compared to each other in regard offiltration performance, filtrate quality, and operational costs. The paper will presentthe pilot results of inge water technologies AG, which was finally chosen to supplythe water treatment plant with 208 UF module type dizzer XL0,9MB60, and the wayto the large-scale UF - plant.The preliminary examinations done during the pilot test period can be divided intotwo main pilot phases, which differ in arrangement of the individual process stagesand therefore in pre-treatment of feed water to the UF. In pilot phase 1,approximately 5 month lasting, pre-treatment before UF was characterised by inlinecoagulation followed by manganese elimination in a multi-media filter and limestonefiltration for hardening and stabilisation of the pH-value. In the following phase 2 thesequence of process stages was changed and pre-treatment before UF consistedonly of inline coagulation, the other stages were arranged behind the UF. Thisconfiguration has been retained unchanged by the end of the pilot tests.For the pilot trials a standard inge UF module dizzer 5000plus with Multibore~?membrane fibres and 50 m~2 active membrane area was used. This PES membraneis characterized by a nominal pore size of 20 nm which ensures a virus-log-removalrate of >log 4 according to >99,99% elimination of MSII phage and a superiormechanical strength due to its Multibore structure.Main focus of the tests was to achieve the highest possible recovery rate whilemaintaining a low level of transmembrane pressure (TMP) and chemicalconsumption for chemical enhanced backwashes (CEB). Furthermore a detailedexamination with the aim to find the optimal coagulant and the optimum of dosageamount, consistent with the current feed water quality, has been carried out to definethe optimum parameters for the hybrid-process coagulation-ultrafiltration. Regardingthe filtrate quality, the major focus was on the removal of organic parameters likedissolved organic carbon (DOC) or removal of UV- adsorption and in particularly theremoval of photosynthetic “Picoplankton”, which make up approximately 70 % of allthe plankton organisms in the Riveris reservoir