Membrane filters can be used for final filtration or prefiltration, whereas a depth filter is generally used in clarifying applications where quantitative retention is not required or as a prefilter to prolong the life of a downstream membrane. Membrane and depth filters offer certain advantages and limitations.
Concrete Hard-standing-When using concrete as a surface to support your new shed, you must ensure that it is level, flat and that it is dry in time for your shed delivery and installation. Here are the basic steps: 1  Using pegs and string, mark out the base area (allow 5 cm extra).
To make the subbase, pour gravel about four inches thick, flatten with a screed rail and check for level. Then tamp down so it is about four inches thick. Flatten and level again. Particularly for projects adjoining or close to the house, make sure the subbase slopes away from the house about 1/8th inch per foot. An additional option is to replace the top inch with a finer gravel or sand base. You can also add the base on top of a full four-inch subbase. The finer base will make it easier to keep the concrete level, and require less concrete, which can be expensive. Once the base is level and thoroughly compacted, check your work by rolling a heavy truck over the base. It should sink uniformly, and the truck tires should not sink more than 1 inch into the soil.