No abstract

The main environmental problem of sewage sludge treatment and storing processes is unpleasant smell caused by emitted gases, such as NH3, H2S etc.; which are released during organic matter decomposition process. The second environmental problem is that during sewage sludge composting process global warming gases, such as CO2, CH4, and N2O are emitted, the emissions of these gases can be reduced by creating optimal composting conditions (C:N, aeration, pH and humidity) and by adding some additives (wood cuttings, shavings, zeolites, peat etc.) into sewage sludge. In our study we analyse the experimental results on CH4, NH3, H2S and VOC emissions during sewage sludge composting process. For this experiment, centrifuge‐dried sewage sludge from Vilnius City Municipal Sewage Treatment Plant were used. Used Ashen bark, oaken cuttings, aspen shavings, shredded deciduous tree branches. The composting process was performed in a compost site‐simulating facilities. Santrauka Nuoteku valymas, nuoteku dumblo apdorojimas ir saugojimas neišvengiamai kelia išsiskiriančiu duju, nemaloniu kvapu problema. Yrant organinems medžiagoms išsiskiria nemalonaus kvapo dujos (NH3, H2S ir kt.) ir šiltnamio efekta sukeliančios dujos (CO2, CH4, N2O). Biodegradacijos procesai vyksta gamtoje ir natūraliai, ir dirbtinai ‐ kompostuojant. Sudarant optimalias kompostavimo salygas (C:N, aeravimas, pH ir dregnis) bei naudojant priedus (medžio pjuvenas, drožles, ceolita, durpes ir kt.) galima mažinti dujiniu teršalu emisijas i aplinka. Nagrinejami nuoteku dumblo kompostavimo eksperimentu rezultatai tiriant CH4, NH3, H2S ir LOJ emisijas. Eksperimentui naudotas perteklinis Vilniaus komunaliniu nuoteku valymo irenginiu nuoteku dumblas, nusausintas centrifugomis. Kaip papildomos medžiagos ‐ uosio žieve, ažuolo pjuvenos, drebules drožles, smulkios lapuočiu medžiu šakos. Kompostuota kompostavimo aikštele imituojančiuose “irenginiuose”. Резюме Oчисткa сточных вод, а также дальнейшая обработка накапливаемого осадка связаны с выбросами газов с неприятным запахом. Газы, образующиеся в процессе деградации органических веществ, не только обладают специфическим запахом (NH3, H2S и др.), но и вызывают парниковый эффект (CO2, CH4, NOx). Известно, что процесс биодеградации может происходить как в естественных, так и в искусственных условиях, например, при компостировании. Используя примеси (опилки, щепки, цеолит, торф и др.), а также подбирая оптимальные условия для компостирования – C:N, аэрация, рН, влага, можно снизить выбросы газов в окружающую среду. В статье проанализированы результаты газовых выбросов – CH4, NH3, H2S, ЛОС – при компостировании осадков сточных вод. В эксперименте был использован избыточный осадок из очистных сооружений города Вильнюса после обработки на центрифугах. В качестве дополнительного материала (примесей) в процессе компостирования были использованы кора, опилки дуба, стружка осины, небольшие измельченные веточки. Процесс компостирования был имитирован в лабораторных условиях.

No abstract

Our experiment was conducted during the summer (seven days) in the seaside recreation area of Curonian Spit, Lithuania, with a view to observe the dispersion of ozone (O 3) and nitrogen dioxide (NO 2) in this territory. In addition, the meteorological parameters (ambient temperature, relative air humidity, wind velocity, and direction) were recorded in order to assess the infl uence of these parameters on the changes in pollutants in the Curonian Spit. During the experiment, the ozone concentration in the spit varied from 5 to 130 μg/m 3 , while the concentration of nitrogen dioxide varied from 1 to 34 μg/m 3. It was found that the meteorological parameters infl uenced the changes in the levels of ozone. The investigation data showed that such meteorological parameters as temperature and relative humidity had the most important infl uence on ozone concentration variations (r = 0.619 (p<0.05); r = 0.612 (p<0.05), respectively). The changes in the level of nitrogen dioxide have been mostly infl uenced by traffi c intensity. O 3 and NO 2 were inversely related. The ozone concentration in Juodkrantė and Preila was higher by 37% than that measured in Klaipėda, while the nitrogen dioxide concentration was lower by 43%. The formation of ozone in the troposphere begins with NO 2 photolysis, after which the NO quickly reacts with ozone to regenerate the NO 2 .

Various methods for removal of volatile organic compounds (VOC) from the air are applied in the world. Their selection is determined by the efficiency and costs of the method. Biofiltration is a new technology to control environmental pollutants helping to regulate emissions of VOC with unpleasant odours in to the air and working environment. When VOC are to be removed from large volumes of air, equipment of biological purification charged with active sludge is used. Such an equipment has a rather simple structure and efficiency of to 98–99 %. Active sludge as a biocharge has both a high concentration of microorganisms compared to stationary charges and good sorption features. Sorptive capacity changes when a load to active sludge is changed, and this has a negative impact on biochemical decomposition of organic substances and, at the same time, on purification efficiency. Calculation and evaluation of an optimal working mode of the equipment enable to avoid desorption of VOC in the system or to diminish it to a minimal value. In the biological air‐purification equipment sorption of an organic substance on the surface of active sludge is running at the initial stage. An organic substance is decomposed biologically only in the second stage, and oxygen dissolved in the system (in the charge) is used and VOC desorption from the system is blocked. One of the main parameters determining the biological air‐purification process and its intensity is change of the concentration of oxygen dissolved (CDO) in water phase and maintenance of its minimal value after termination of aeration (when the equipment is out of operation for some time). In operating equipment with a biocharge one more important problem is encountered ‐ the lifetime of the charge and its renewal in the equipment to maintain required concentration of the active sludge. The goal of the investigation is evaluation of purification efficiency of the equipment and the sorptive capacity of active sludge (depending on a load), selection of the working mode, uninterrupted biochemical decomposition of organic substances (based on the concentration of dissolved oxygen) when the charge is in its still state, and investigation of its biooxidating properties when a biofilter works with a biologically active charge and with an inactive charge having only sorptive properties.