Rolf Kayser

PROCESS CONTROL AND EXPERT SYSTEMS FOR ADVANCED WASTEWATER TREATMENT PLANTS

ABSTRACT Stringent effluent standards for nitrogen and phosphorus require a certain extent of process control in order to respond to the diurual and seasonal fluctuations of the loads and to save energy and chemicals. The concentration of ammonia at the effluent of the aeration tank is a key parameter to control the whole aerobic process. The nitrate concentration or the redox-potential are useful to control the denitrification process. If enhanced biological phosphate removal is employed, in many cases additional chemical phosphate precipitation is necessary. The phosphate concentration of the effluent of the aeration tank is useful to control the feeding rate of precipitant for a supplementary simultaneous precipitation. Operators of smaller plants, due to their often limited background, are overtaxed by the complicated biological and chemical processes of advanced wastewater treatment even if continuing education and training at the job are provided. It, therefore, is also necessary to provide a “computer expert”, which should contain technological expert knowledge and the peculiarities of the plant, and it should read and evaluate the on-line and lab data.

FULL-SCALE EXPERIENCES WITH BIOLOGICAL PHOSPHORUS REMOVAL AT THE WASTEWATER TREATMENT PLANTS OF WEST BERLIN

In investigations concerning sludge bulking in Berlin enhanced biological phosphorus removal was first observed unexpectedly. Because since 1986 an officially preset limit of 2 mg TP/l must be kept in all Berlin wastewater discharges it was decided to explore the capabilities of the observed mechanism under the specific circumstances of the existing two large treatment plants in Ruhleben (240, 000 m3/d) and Marienfelde (100, 000 m3/d). For this purpose some of the existing units at both plants were equipped with anaerobic zones which were generated mainly by process modifications. Additionally stage one of the Ruhleben plant was altered completely in order to investigate the combination of biological phosphorus and nitrogen removal as a special pilot study in three parallel trains. The research activities and treatment results gained in each of the two stages of the Ruhleben and in the Marienfelde plant are reported in detail. For example BOD-related phosphorus removal rates were obtained ranging from 2.3-4.5 mg TP per 100 mg BOD removed. It must be stressed that all examinations were performed under full-scale conditions. At present the given limit of 2 mg TP/l in the Ruhleben plant is met without any chemical precipitation at least on average. From the beginning biological phosphorus removal will be integrated into further projected extensions.

Erarbeitung von Bemessungs-Grundlagen

Zur Ermittlung der Grundwerte fur die Erweiterung einer Klaranlage in Norddeutschland wurden von Juni bis Oktober 1963 Untersu-chungen durchgefuhrt. Die Anlage bestand aus Vorklarbecken, Tropf-korper und Nachklarbeeken. Der Schlamm wurde in Poldern abgela-gert. An die Anlage waren angeschlossen eine Stadt mit rd. 45.000 Ein-wohnern, ein chemisches Werk fur die Produktion von Bioziden und eine Gemusekonservenfabrik. Die Kanalisation ist nach dem Trennsystem angelegt.