|| Form and design of reactors is determined based on diverse factors such as the type of mixing, necessary discharge techniques for sink and swim layers, substrate characteristics and built-in components. The accumulation of sediments in the reactor should be avoided for disruption-free operation. The discharge systems for the removal of sediments from the reactor space should be planned, if accumulation due to the mixing components can not be avoided with certainty. Standing cylindrical reactors are sometime equipped with a conical reactor floor that allows for the removal of sedimented material in its point. Difficult constructive designs can be avoided if the reactor floor is planned with, for example, a small slope. The sediments are transported to the centre due to the so-called "tea cup effect" and can be selectively removed there. A further possibility lies in the coneshaped design of the reactor floor, through which the sediments make their way into outer-lying sloped gutters. The sediments are removed from the fermentation space at two places opposite of one another with the use of feed spirals. Discharge devices can also be carried out in the form of a drawer or similar mechanical apparatus. This discharge devices are used, for example, in lying plug-flow reactors. The avoidance of accumulation is also possible with the directed addition through pressing of fluids or substrate.