Microbiological evaluation of sewage sludge in terms of possibilities of application in soil as a fertilizer

Research was conducted of sewage sludge from wastewater treatment plant for the existence of microorganisms of several major groups, containing pathogenic representatives with epizootological significance (Gram-negative aerobic bacteria, E. coli, Clostridium perfringens, the genera Pseudomonas, Staphylococcus, Enterococcus, fungi, and the total number of microorganisms), in order to assess the environmental safety of the final product. In parallel similar studies were made of fresh and composted cattle manures. A comparison of the results was made with the ready for manuring compost in order to assess the possibilities for the use of sludge for fertilizing. The quantities of microorganisms were given in CFU per 1 g of the investigated material, as well as per 1 g of dry substance for each of them. In our opinion this new approach to the reporting of the results per unit of dry matter of the investigated materials, allows for a more accurate comparison. It was found that the examined sewage sludge from wastewater treatment plant were rich in microorganisms from studied groups and their direct application in soils without prior treatment by aerobic or anaerobic digestion may represent epidemiological danger

Agroecologic valuation of organic waste in different technologies of storage

A study has been conducted, based on three types of fertilizers / cow, pig and bird manure/ and bioshlam /received from clearing station/ that have been storage in different technologies in order to make an agroecologic valuation. The different types of fertilizers and wastewater in different technologies of storage have been analyzed according to the following parameters: Dry matter (DM) ,Organic matter (OM), Organic Carbon (OC), Nitrogen Kjeldahl (N), Nitrogen Ammonium (N -ammonium), Nitrogen nitrate (N- nitrate), Sulfates (SO4) , Calcium Oxide (CaO), Magnesium Oxide (MgO), Patassium (K), P (Phosphorus), pH (H2O) and heavy metals – arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Mercury (Hg), Nickel (Ni), Lead (Pd), Zinc (Zn). The received results show: variation of the percentage of dry material /from 92,12% to 4,03%/ according to the technology of storage. The way of storage has no essential influence on the content of carbon in the various stable fertilizers, where pig manure has the highest value of nitrogen in all technologies of storage. Near to the recommendable optimal values of C:N is stayed/dry/ and fresh/hard/ in all three fertilizer types. The technology of storage by the different manure types has no influence on the content of heavy metal. Exception can be observed as far as the zinc content in stale /fluid/ pig manure is concerned. High content of dry material can be observed in bioshlam received from clearing station. In both ways of production of variation in the content of dry material the ratio between the biogenic macro elements C:N remains. The free nitrogen forms (N-ammonium and Nnitrate) in bioshlam are higher to other organic waste in both technologies of storage. No values over the critically admissible in bioshlam are observed in both technologies of production

Microbiological and epizootological characterization of materials from wastewater treatment plant

Studies were carried out for the presence of microorganisms of major groups, containing pathogenic agents with epizootological importance, in order characteristic of their dynamics at different levels in the treatment plant and assessing the environmental safety of the final materials. For this purpose were traced the changes in the quantities of microorganisms contained in the materials from successive levels of processing. It was found that the purified water inlet and outlet does not contain Salmonella enterica. Presence of Escherichia coli and Clostridium perfringens beyond the requirements of the regulation (Decree N339, 2004) was not established, as well as Enterococcus spp. The tested sludge contained microorganisms from these groups and could not be deposited in the soil without prior aerobic or anaerobic processing. The draining in the nature of treated water at the outlet of plant does not hide environmental risk. In addition to monitoring of the sanitary indicative bacteria, the following of the main groups of Gram-negative and Gram-positive microorganisms in the water and sewage sludge allows more reliable assessment of their decontamination. Furthermore, the new approach for reporting the results in a unit of dry matter of the studied materials, proposed here, allows their more exact comparison

Reduction of sanitary indicator microorganisms in anaerobic digestion of poultry litter in combination with silages

ABSTRACT: In connection with experiments aimed at optimizing anaerobic digestion of organic fertilizers, microbiological tests were performed to assess the epizootiological safety of resulting finished product to fertilize the soil by quantities of sanitary indicator microorganisms. Mixtures of substrates were composed and tested in technological parameters established for other experiments: mesophilic temperature regime 33oC, dry matter content of 7%, residence time in the digester 15 days. The substrates tested were beetroot, sugar and salad beets, corn silage and leaves of Paulownia elongata, and silage combinations of these feeds in ratio 60:40 with mulch litter from broiler chickens. It was found that significant reduction of microorganisms was realized in the final products, which were assessed as safe for soil application. The ensiling of poultry litter in combinations of these feeds had the effect of reducing the amount of microorganisms in almost all examined groups therein. The most significant was the reduction in the quantity of sanitary revealing bacteria in the manure after its ensilage with autumn leaves of P. elongata and beetroot, and the least - with the participation of sugar beet. Microbial reduction was to the greatest extent in bioslime produced by anaerobic digestion of poultry litter ensiled with corn. Of the silages from different types of beets with poultry manure, during anaerobic digestion highest decontamination was achieved in this with sugar beets. After anaerobic degradation of the studied feed without poultry litter, at least microorganisms were found in bioslimes from the three types of beet, as well from the silage from P. elongata. РЕЗЮМЕ: Във връзка с експерименти, насочени към оптимизиране на анаеробното разграждане на органични торове, са извършени микробиологични изследвания за преценка на епизоотологичната безопасност на получените крайни продукти за наторяване на почви според количествата на санитарно индикаторните микроорганизми. Съставени са смеси от субстрати при установени при други експерименти технологични параметри: мезофилен температурен режим 33оС, съдържание на сухо вещество 7%, време на престой в биореактора 15 денонощия. Изпитани са захарно, кръмно и салатно цвекло, царевичен силаж и листа от Paulownia elongata, както и силажи от комбинации на тези фуражи в съотношение 60:40 с торова постеля от пилета-бройлери. Установено е, че се осъществява значително редуциране на микроорганизмите в крайните продукти, които се преценяват като безопасни за внасяне в почвите. В най-голяма степен микробната редукция е при биошлама, получен при анаеробното разграждане на комбинацията от торова постеля с царевичен силаж. От трите вида цвекло, силажирани с птичи тор, при анаеробно разграждане се постига най-висока деконтаминация с участие на захарното цвекло. При анаеробно разграждане на изследваните фуражи без птичи тор най-малко микроорганизми се установяват в биошламовете от трите вида цвекло, както и в силажа от P. elongata

Microbiological evaluation of sewage sludge in terms of possibility of applications in soil as a fertilizer

The studies were carried out of sewage sludge from wastewater treatment plant for the presence of microorganisms of several main groups, containing pathogenic representatives with epizootological significance (Gram-negative aerobic bacteria, E. coli, Clostridium perfringens, the genera Pseudomonas, Staphylococcus, Enterococcus, fungi, and the total number of microorganisms), in order to assess the environmental safety of the final product. In parallel similar studies were made of fresh and composted cattle manures. A comparison of the results was made with the ready for manuring compost in order to assess the possibilities for the use of sludge for fertilizing. The quantities of microorganisms were given in CFU per 1 g of the investigated material, as well as per 1 g of dry substance for each of them. In our opinion this new approach to the reporting of the results per unit of dry matter of the investigated materials, allows for a more accurate comparison. It was found that the examined sewage sludge from wastewater treatment plant were rich in microorganisms from studied groups and their direct application in soils without prior treatment by aerobic or anaerobic digestion may represent epidemiological danger