The Treatment Plant
The Treatment Plant for Education and Research (LFKW) is situated west of Stuttgart near the village of Büsnau and near to the Rot- und Schwarzwildpark Nature Reserve. The catchment area includes the residential area of Lauchhau-Lauchäcker next to Brüsnau, the Bärenschlössle, and almost the entire University Campus in Vaihingen Pfappenwaldring.
This sewage treatment plan has been in operation since the 1965. Between 1989 and 1992, it was gradually extended and rebuilt to properly meet the increased waste water treatment quality standards.The pollution load, which is supplied to the LFKW, equals that of about 10,000 inhabitants. On average, about 2,000 cubic meters of wastewater is treated daily.
The hydraulic capacity of the plant is 30 liters per second. During high flow events, excess flow is discharged through a tunnel to Stuttgart. This 2.7 kilometer long tunnel was completed in 1978 and serves as a stormwater retention basin. The effluent of the sewage treatment plant is discharged into the Bandtälesbach, which, after a short distance, flows into the Glems. The effluent eventually flows from the Glems to the Rhine River via the the Enz und Neckar rivers.
What differentiates the LFKW from other Sewage Treatment Plants?
Its foremost difference is its multi-pronged cleaning system. All equipment and mechanical processes in the various process steps are at least doubled. Portions of the main flow stream can be rerouted to different treatment components and process that operate independently form regular operation. This allows for multiple wastewater treatment schemes to be researched and compared in an industrial scale without degrading the quality of the final effluent. Therefore, unlike other wastewater treatment plants, the wastewater of the LFKW is not treated following a rigid treatment scheme, but a flexible one.
The wastewater and sludge pipelines, for the most part, are installed in large underground access tunnels. In order to provide the unique flexible flow schemes for wastewater research, a total of over 10 kilometers of pipelines are used.
The timeless concept
The original concept of the entire system, as well as the planning of the individual facilities, is based on the following demands which must be observed in the course of subsequent renewal measures:
- the proper treatment of incoming wastewater must be ensured at all times and is an absolute priority
- the facilities must be flexible, so they can be used for research and development in both technical and semi-industrial scales
- the components of the treatment plant should serve as demonstration and practice items and thus support the practical teaching of the Institute
The LFKW as a Disseminator
The results from more than for decades of research in the LFKW have developed and determined the current state of wastewater and sludge treatment in the Federal Republic of Germany. Through the flexible technical configuration of the plant and the continuous availability of different wastewater and sludge compositions for experiments ensures, even on a small scale, the customization to new research tasks at any time. The operational pilot plant represents the current state of science and technology. Therefore, many foreign and domestic scientists and professionals visit the LFKW with great interest.
In sense of one of the original objectives, the LFKW has become an indispensable means of practical training through ISWA courses as a demonstration plant. Here students can work on their Diplom, Bachelor, or Master thesis within the framework of the offered courses and internships, or they can work as research assistants and become familiar with the details and operation of a high-tech wastewater treatment plant. Naturally, students can gain a lot of experience and knowledge at the LFKW in conjunction with regular lectures and seminars.
In addition to the responsibilities in research, education and training, the LFKW also offers services for companies. The services are primarily in development and testing of investment techniques, technical instruments and auxiliary materials. In addition, LFKW staff provides on site technical assistance in the preparation and implementation of studies to determine solutions for operational and managerial problems.
The LFKW also supports communities, commercial operations and engineering firms with further services: form the fabrication of custom laboratory testing facilities for pumps, samplers and measuring equipment; to renting complete semi-industrial pilot plants for wastewater, sludge and air treatment, including transportation, installation, and startup.
In closing, one must no forget that the heart of the Institute and the LFKW lies not only with the mandatory research and education they provide, but also with the training of wastewater treatment personnel. Since 1967, basic and advance courses in Sewage Works Operation and Channel Maintenance have been performed in cooperation with the DWA-Landesgruppe Baden-Württemberg. The LFKW has become known across the world due to the different courses and unique functions it provides. For several years, the LFKW has conducted several week long training courses for foreign wastewater treatment plant operators.
Facilities for Wastewater and Sludge Treatment
The wastewater treatment at LFKW is based on state of the art technology with the goal of eliminating nitrogen and phosphorus compounds (ammonium-N, inorganic-N, and total-P), particulate waste (filterable substances) and the most extensive oxygen consuming organic matter, which is measured as Biological Oxygen Demand (BOD) or Chemical Oxygen Demand (COD). The unique design of the LFKW enables the plant to be modified to meat the considerably increasing demands by changing the flow scheme which would not require a large extension of the plant. However, due to the advanced age of most of the plants components, the need of repairs and rehabilitation steadily increases.
In the course of wastewater treatment, the following equipment and process steps can be used:
- Two underground tanks (each w/ 570 m 3 vol.) located at the inflow of the plant and used for stormwater retention basins or emergency wastewater storage tanks
- Two mechanically cleaned course screens (have a counter-flow rake with 30 mm bar spacing) to remove course material from the incoming wastewater. The screenings are collected and the organic and inorganic fractions are separated in a rotary press.
- Two fine screens with integrated dewatering of screenings (perforated sieve with 5 mm holes) to prevent blockage and scum formation in the following processes.
- One aerated grit chamber and one vortex grit chamber to separate solids from the wastewater. The organic and inorganic fractions of the removed solids are then separated in a Classifier
- Two small basins (each w/ 16 m 3 vol.) with aeration systems that are used today for storage of sludge water.
- One small primary clarifier (51 m 3 vol.) and two large primary clarifiers (each w/ 95 m 3 vol.) used for course sludge treatment and scum removal, or settling of suspended solids and storage.
- One rotating biological contactor (RBC) with a total of 6,000 m 2 of disk surface area for aerobic biological wastewater treatment with or without nitrification.
- One oxidation ditch (116 m 3 vol.) and two rectangular secondary sedimentation tanks (w/ 30 and 15 m 3 vols.) for biological wastewater treatment with or without specific nitrogen removal by intermittent denitrification. Aeration and circulation by a mammoth rotor and agitator.
- One funnel-shaped tank (290 m 3 vol.) with a mixer for pre-denitrification. This tank is where anoxic conditions exist and the nitrate-containing wastewater, which has just finished mechanical treatment (i.e. screening, primary sedimentation), is mixed with return sludge and the internal recycle stream of the aeration tank.
- One storage and metering station for carbon-containing substances to improve the upstream denitrification process (13 m 3 storage tank).
- Four aeration tanks (each w/ 110 m 3 vol.) arranged in series for nitrification using fine-bubble aeration from the tank floor. The first tank is equipped with an agitator for intermittent denitrification.
- One indoor storage and dosing tank (7.2 m 3 capacity) for the chemical removal of phosphorus by precipitation.
- Two secondary sedimentation tanks (each w/ 140 m 3 vol. and 55 m 2 s.a.) One tank is divided into a vertical and a horizontal flow part while the other has only horizontal flow.
- One vertical flow, funnel-shaped secondary sedimentation tank (290 m 3 vol. and 109 m 2 s.a.) to separate activated sludge.
- Two indoor micro-screen drums (each w/ 2 m dia. and length covered w/ micro-fabric w/ 15 to 20 μm openings) in conjunction with upstream flocculants for the further removal of suspended solids and phosphorus from the secondary sedimentation effluent.
- Two fish ponds (w/ 80 and 110 m 3 vols.) for the further treatment of the wastewater treatment plants effluent.
The resulting sludge from the wastewater treatment is concentrated and then anaerobically stabilized. The resulting biogas is completely recovered.
In total, the sludge treatment has the following:
- Two tanks (12 m 3 vol. each) for the temporary storage of sludge
- A station for mechanical sludge dewatering using a centrifuge
- Three biofilter containers (12 m 3 vol., 10 m 2 s.a., filter layers consisting of bark humus and expanded clay) for the biological treatment of the exhaust gasses from the sludge dewatering
- Two heated digesters (320 m 3 vol. each) for the anaerobic stabilization of the incoming sludge or for sludge storage. Recirculation occurs by means of rising biogas or pumping
- One sludge sump for the dispensing of the digested sludge or for the introduction of external sludge or putrescible refuse into the digestion tank
- A round tank (160 m 3 vol.) for the temporary storage of the digested sludge
- Two combined gravel and condensation traps and a dry desulfurization system for biogas cleaning
- A gas tank (100 m 3 usable vol.) for the temporary storage of the biogas before its use for electrical energy production and heating purposes
The individual process steps of wastewater and sludge treatment are carefully controlled. Extensive measurement instrumentation, about 120 processes are continuously monitored as well as regular wastewater and sludge analysis in the laboratory, make the sub-processes transparent and provide the basis for the ongoing plant optimization through use of control and regulating devices. All measured variables and operating conditions are monitored, automatically evaluated and documented using modern process control system
The wastewater and sludge treatment facilities and equipment are supplemented by:
- The operations building with central control room (the place where the process control system for surveillance and regulation of the sewage treatment facilities is installed) with offices, laboratories and a lecture hall.
- A two-story experimental hall with affiliated workshops.
- The energy building with the heating system (can operate with biogas and natural gas), transformer station and a further workshop.