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SZOSTKOVA, M., VITĚZ, T.: Primary treatment of the waste water treatment plant from the point of view of the current legislation. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 2, pp. 205–212 This contribution focuses on an analysis of sand from nine diff erent wastewater treatment plants in South Moravian Region. We conducted an analysis and evaluation of microbial properties of sand in accordance to Act No. 185/2001 Coll. on waste as amended, resp. Decree No. 381/2001 Coll. Content of following parameters were monitored, thermotolerant coliform bacteria, coliform bacteria, enterococci, total solid, ash free dry mass. We encountered several interesting fi ndings, which pertained mainly to the content of microorganisms in sand. Knowledge of microorganism content should show, how the primary treatment of the wastewater treatment plant works, and should be very interesting indicator. wastewater treatment, primary treatment, detritus tank, wastewater treatment sand, microbial contamination, mechanical properties Primary treatment of domestic wastewater represents an extensive range of physical and chemical activities which directly or indirectly aff ect fun ctiona li ty of the treatment plant as a whole. The aforementioned eff ect might be rather signifi cant in many respects. The respective matter proves to be highly underestimated (by both operators and designers) at many treatment plants. However, an incorrectly designed or operated primary treatment might result in an unnecessary increase of operating costs and should have a negative impact on the biological level or sludge treatment and disposal. A detritus tank proves to have a key role in the process of primary treatment. The principal task of a detritus tank is to collect the maximum possible amount of mine ral substances from wastewater in a manner ensuring that organic substances will remain present in the upli and they are to fl ow to the subsequent treatment level. The structure of a detritus tank is to ensure that solely sand without any organic substances will be settling down. However, it is highly complicated to achieve these conditions considering the high level of infl ow irregularity, and therefore a high level of concentration of organic solids in the excavated material (Fujioka et al., 2001). Furthermore, a detritus tank performs also a protective function, which means that it protects other equipment complexes against excessive wear and tear. A correctly rated detritus tank is supposed to catch all sand, i.e. mineral particles featuring the grain size above 0.2 mm and specifi c density of 2400 kg/m3 or more (Claydong et al., 2001). This means that a detritus tanks is to be rated in a manner ensuring that wastewater will fl ow through it at a constant speed in all fl ow conditions. Should a detritus tank fail to function, the mixture of organic material and sand creates a sediment layer that causes major problems in the following stages of wastewater treatment. The scope, however, does not comprise solely damage caused to machinery (abrasion) but also problems or even elimination of correct functionality of – mainly – sludge treatment and disposal (sludge thickening, sludge digestion tanks, etc.) due to blocking of pipelines as well as sedimentation in tanks resulting in a more complicated stirring of tank content and limitation of their volume that feature numerous negative consequences as 206 M. Szostkova, T. Vitěz regards of their operation. Cleaning of such tanks results in origination of major operating costs to be covered by the party operating the respective WWTP. A solution to the matter of sand removal prior to discharge of rainwater in the sewerage system or infl ow into storm tanks at WWTP represents a separate section. This matter proves to go beyond the scope of this contribution; however, it is to be emphasized that a failure to solve such a problem results not only in clogging of recipient channels by sand, thus limi ting their profi le, but also in introduction of organic substances that had o en gone through a partial anaerobic decomposition and create sludge beds featuring a very long natural oxidation period in the water fl ow. Sand separated in the wastewater treatment process may, however, contain pathogenic germs of microorganisms that would – in high concentrations – represent a risk pertaining to its subsequent treatment (Schroeder and Wuertz, 2003). Legislative Requirements As regards the legislation, the matter of treatment of sand from wastewater treatment plants is not thoroughly covered. Considering the valid le gisla tion, principally Act No. 185/2001 Coll. on waste as amended, resp. Decree No. 381/2001 Coll. laying down the Catalogue of Wastes as amended, sand from a detritus tank is – in accordance with Annex No. 1 to the Decree – included in the Catalogue of Waste under the name of “Waste from detritus tank” and ref. No. 19 08 02 as other waste (O) and such sand is handled in the respective manner. This practice is enforced in spite of the fact that such waste might feature minimum one of the hazar dous pro per ties stipulated in Annex No. 2 to Act No. 185/2001 Coll. or contain one of the components due to which waste is regarded as hazardous in accordance with Annex No. 5 to Act No. 185/2001 Coll. The property referred to above is contingent contagiousness. Therefore, we conducted microbiological analyses of sand from wastewater treatment plants. As suggested above, an unambiguous procedure applicable to sand from wastewater treatment plants does not exist and due to this fact the guidelines applicable to handling of wastewater treatment sludge – more specifi cally Decree No. 382/2001 Coll. on conditions of the use of treated sludge on agricultural land as amended – were selected to serve as a basis. The aforementioned Decree stipulates the technical conditions applicable to use of sludge on agricultural land as well as limit concentrations of selected hazardous substances in sludge and soil including microbiological criteria. The Decree also stipulates admissible amounts of indicator microorganisms (Tab. I). The scope covers thermotolerant coliform bacteria, enterococci and Salmonella sp. Considering the most common manner of sand removal by the means of disposal, it is necessary to face additional legislative requirements resulting from the valid judicial practice. The respective scope covers principally the conditions applicable to depositing of sand from a detritus tank in a landfi ll. They are governed by Decree No. 294/2005 Coll. on the conditions of depositing waste in landfi lls and its use on the surface of the ground (as amended). The aforementioned Decree expressly stipulates the conditions upon which sand from a detritus tank may be deposited in a landfi ll. As regards other waste, the Decree specifi es three subgroups of landfi lls (S-OO1, S-OO2, S-OO3); sand from a detritus tank may be deposited in landfi lls labelled S-OO1 and S-OO2 – on the basis of expressly specifi ed conditions that are stipulated in Annex No. 4 to Decree No. 294/2005 Coll. Considering the conditions sti pu la ted in Annex No. 4 to Decree No. 294/2005 Coll., the most signifi cant problem proves to be related to the total content of organic carbon (TOC) which should remain under 5%; in case of exceeding TOC, the problem pertains to dissolved organic carbon (DOC) which is monitored in the aqueous li quor of deposited sand and in case of which the value should not exceed 80 mg/l. The eff ort focused on prevention of depositing slowly organically decomposable materials in landfi lls resulted in incorporation of TOC and DOC parameters into our judicial practice and causes numerous problems. The most signifi cant problem pertains to an exact defi nition of the respective terms as well as selection of a suitable analytical method applicable to determination of TOC and DOC – due to the fact that in practice it is possible to encounter diametrically difI: Microbiological criteria: Use of sludge on agricultural land I: Sludge category Admissible amount of microorganisms (CFU*) in 1 gram of solids of applied sludge Thermotolerant coliform bacteria Enterococci Salmonella sp.