Investigation Into Emissions of Gaseous Pollutants During Sewage Sludge Composting With Wood Waste

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.

Experimental Tests on the Influence of Waste Covering Layer on Odour Reduction

“…Emissions of the hydrogen sulphide whose odour threshold equals 0.012-0.03 mg/m 3 are reduced with the help of crushed wood bark [9]. H 2 S emissions from compost mixed with bark are lower than those from compost covered with bark.…”

Characterization of the Gaseous and Odour Emissions from the Composting of Conventional Sewage Sludge

“…However, [42] evaluated the OEFs of different substrates in a 300 L aerated pilot-scale reactor, reporting an OEF of 9.35 × 10 8 ou•Mg −1 DM-SS for SS composting and [24] obtained an OEF of 9.45 × 10 7 ou•Mg −1 DM-SS in a full-scale sewage sludge composting plant. For SS composting, different ranges of target pollutants and odour concentrations can be found in literature depending on the characteristics of the feedstocks or the composting process itself [43][44][45]. Figure 4 shows the daily odour emission rates (OER) obtained during the SS composting process, together with the average temperature of the reactor and the specific airflow.…”

Co-composting of solid waste and fecal sludge for nutrient and organic matter recovery

“…But quick oxygen depletion may cause anaerobic conditions. In addition, the composting process will experience higher losses of N as ammonia and nitrogen oxides because inorganic N is generated in excess (Bernal et al 2009;Zigmontiene and Zoukaite 2010). Both phenomena are the main reason for odor generation due to wrongly set C:N ratios of input materials in compost plants.…”