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world pulppaper 83 thestresslevel experiencedby microbiological populationsis measured asBsiBio stressindex averyuseful parameter when monitoring toxicityin andaround bioreactors Figure 3. Compact flocs after a Ferric based chemical has been added in activated sludge5 Figure 4. Schematic describing the key components of sludge in biological processes6 Living Biomass Dead Biomass and inert Organics Living Biomass Dead Biomass and inert Organics and inert inorganics Living Biomass Only Environmental discharge limits had been exceeded for several months in a row solution The filaments were identified by gene probe technique as Alphaproteobacteria and addition of FennoNutri to the biological treatment in order to stabilise the process was proposed results Effluent treatment is working according to permit No need for filament killing in the WWTP savings Not analysed in this case TSSVSSAVSS mOnitOrinG BiOLOGiCaL aCtivity anD sLuDGe inventOries Activated sludge processes often carry large solids inventory and managing this is a key component of the optimisation process. Kemira has together with the Canadian company LuminUltra developed the LumiKem test kit to measure biological activity based on ATP. This measurement of the active volatile suspended solids AVSS helps quantify the living biomass in the activated sludge process Figure 4. This information assists in optimising sludge inventories and ensuring that sufficient biomass is present for degradation of the wastewater constituents. ATP measurements can also be used to alert operators if any components toxic to bacteria are present in wastewater. The stress level experienced by microbiological populations is measured as BSI Bio Stress Index a very useful parameter when monitoring toxicity in and around bioreactors. Proper feeding of nutrients allows the living biomass to re-populate. tertiary treatment In Asia Pacific and Central Europe many mills are using coagulation and flocculation with inorganic chemicals and polymers as a final tertiary treatment to decrease COD to acceptable levels. The method is very effective and capable of removing 60-80 of the organic matter. In China a special process utilising hydroxyl radicals called the Fenton or FennoTriox process is commonly used to remove more than 80 of residual COD. Case stuDy FennoFloc Efficient tertiary treatment Grade Kraft pulp Challenge A mill wanted to significantly decrease discharge values. The mill was obliged by the government to rebuild the aeration process with new activated sludge treatment capacity to meet up with common standards for wastewater regulations and permits products is a very cost effective way to increase the capacity and boost biogas production. Case stuDy Fennonutri Addition of micronutrient stabilizes the biological treatment plant Grade RCF and Bleached Mechanical Pulp Challenge The biological treatment was not functioning very well. Unidentified filaments caused bad settling high discharge of suspended solids and nutrients and loss of biomass