Design Approach
The following approaches can be chosen.
The phase separation stage can be chosen as conventional separation stage according to DWA (1991, 2000) or as membrane bioreactor according to the recommendations of the Ministry of the Environment and Conservation, Agriculture and Consumer Protection of the German State of North Rhine-Westphalia (MUNLV).
The design values are proposed by the program according to the effluent standards. Therein you can assume the recommendations of the North Rhine-Westphalia state agency for nature, environment and consumer protection(LANUV-NRW) or define your own design values. For an international range of use the effluent standards of The European Economic Community are included as well (91/271/EEC). It is possible to design for 24h-effluent standards and for annual effluent standards.
Phosphorus Elimination
Different precipitants for phosphor elimination like Fe-salt and aluminium-salt can be selected. Even an own definied precipitant can be saved. EBPR-approaches (according to DWA, BOLL, WENTZEL) are included as well.
Membrane Technology
Membrane technology represents a promising tool to help solve the conventional problems of waste water treatment as well as to include new challenges taking into consideration economical aspects. For example if an extensive hygienication of the discharges of biological treatment plants required, membrane aeration plants are the process of first choice. Also in industry product integrated steps take hold increasingly, for example membrane steps for processing and recirculation of process water. The suitability of membrane technology for the systematic elimination of dangerous substances has been proved in several research projects. The number and the range of applications is growing gradually with the continuous technical progress. In order to make allowance for the increasing meaning of membrane aeration plants in the context of waste water treatment, a new tool for the dimensioning of membrane aeration plants has been developed and implemented into the design2treat software.
The dimensioning of membrane aeration plants has to be mentioned, which is hereafter described in detail.
Design of membrane aeration plants: The design bases for the dimensioning of membrane aeration plants in design2treat are based on the DWA work sheet A 131 respectively on the university group approach and on the recommendations of the ministry of the environment NRW in its published report "waste water treatment using membrane technology" (MUNLV 2003). This report which is also called "membrane guide" contains for the first time concrete suggestions and correspondingly guidelines for the dimensioning of membrane aeration plants. According to the guidelines of the membrane guide the following aspects have to be considered in contrast to the dimensioning of conventional aeration steps:
Furthermore it is included that in line with a dimensioning according to the DWA-work sheet A 131 or the approach of the university group with the input parameter of a solids content of 12 to 16 g/l the required minimum flow time of 6 hrs can be fallen below. In that case the previously calculated volume of the aeration tank has to be increased by 50 % at most. In order to make allowance for future development and new cognitions regarding the design of membrane aeration plants the dimensioning input can be specified variably.
The results of a dimensioning of a membrane aeration plant with the design2treat software are not only restricted to the output of the required tank volumes but contain also recommendations for sectioning of the volumes for example the size of the volume that has to be constructed for variable aeration or the size of a eventually required compensation volume. Moreover the required volume for the membrane step and the required amount of air for the membrane flushing depending on the manufacturer's instructions can be determined.