wastewater line Wasserfeld

Wastewater treatment process

The sewage treatment plant was dimensioned and engineerized for a 40.000 inhabitants equivalent capacity, in the way to satisfy the needs of population in local areas, of tourism, of industry and artisan shipment, guarantying in the meanwhile higher levels in quality, with the maximum efficiency in organic pollutant load knocking down and phosphoric and nitrogen components strong reduction.

The target of sewage treatment is reached with physical, biological, chemical and biochemical processes.

Legend Function diagram

Water	sludge	Gas

1) inflow	10) Pre-thickener	15) gas accumulator
2) rain relief	11) Digestion chamber	16) gas torch
3) screening plant	12) Post thickeners	17) gas utilisation
4) Aerated grit chamber	13) sludge press
5) Preliminary clarifier	14) sludge disposal
6) Biological basin
7) Final clarifier
8) drain
9) Rienz River

The mechanical sewage

The mechanical sewage, with a 25% organic load reduction efficiency, is assured by a spire screen [3], by aerated grit chamber [4], bar-screens and primary clarifier [5].

Biological cleaning

After that, the sewage treated mechanically cross a series of 3 cascade [6]: in the first one, in totally oxygen absence, takes place the bio-chemical process of partial phosphoric compounds deleting, in the second one, the nitrous compounds reduction is realized (denitrification) while in the last one, the bigger one, atmospheric oxygen is injected to permit la biodegradation of organic compounds and nitrous compounds oxidation (nitrification).

The recycle of vented sewage, of actives sludges and the regulation of oxygen concentration, permit the creation of an ambient in which microorganisms and various nature batteries may easily do the proper work of degradation of pollutant load. These microorganisms, in bow structures, are the actives sludges that are separated by sedimentation in the big secondary clarifier [7]. The last reduction of phosphoric compounds is obtained by simultaneous precipitation (adding chemicals agents).

Biological cleaning — Activated sludge under the microscope

final clarification

The water’s superior layer, now purified, flows out on toothed threshold [7], is analyzed by a measurement and metering station ( for quality and flow rate), and flows out into Rienz river [9].

Sludges treatment line

The sludge coming from the first clarifiers (primary sludge) [5] is thickened mechanically by pre-thickeners [10]. The sludge is now eliminated from secondary clarifiers [7] and thickened mechanically by screencloth. The pre-thickened sludges are now reached at a temperature of 38°C approx and digested into an anaerobic digestion chamber [11].
The sludges, now stabilized and neutrals, are dried with a chamber filter press [13].

Gas line

During the digestion process [11], the microorganisms transforming the organic compounds on CO₂ and methane with high energetic content, available for thermal heating of digestion chambers and for factory heating. To take a solution at the gas over production, in Wasserfeld plant is provided a storage gas tank [16].

The gas line is composed by:
gas flare [15], gasometer [16], pressurization station, 2 heaters and 2 cogeneration groups [17].

Ventilation system

During Wasserfeld plant engineer studies, a special importance matter was the particular attention at stinks emissions monitoring. Stink air coming from fine bar screen, is adsorbed with compressors and biologically treated into the oxidation basin. The stink air coming from the sludgestreating plant is located in warehouses with the proper air treating system.
The stink air, until a flow rate of 15.000 m³/h, is chemically purified with scrubber at crossing flows system with, storing the thermal energy and biologically purified with a 532 m² sized bio filter.

Components and Power

For sewerage system and sludges treatment were provided a total amount of 150 units divided into instrumentation, machineries, for a total amount of power consumption of approx 220 kW; the same items quantity were necessary for heating system, ventilation, air treatment, lightness systems, hydro feed exc.. For power
plant, control and regulation of all these plants and systems, 25 km of bundles and cables were provided.