Ülkemizde atıksu arıtma çamurlarıyla ilgili en yaygın bertaraf yöntemi depolamadır. Mekanik susuzlaştırma ekipmanlarıyla %20-30 Katı Madde (KM) içeriğine ulaştırılan atık çamurlar doğrudan veya kireç ilavesinden sonra düzensiz veya düzenli depolama sahalarına depolanmaktadır. Bu çalışmada atıksu arıtma çamurlarının güneş enerjisiyle kapalı yataklarda kurutulması incelenmiştir. Ülkemizin güneş enerjisi potansiyelinden yararlanmak ve çevre yatırımlarında yenilenebilir enerji kaynaklarının kullanımının yaygınlaşması çalışmaya temel oluşturmuştur. Deneysel süreç için 2m x 5m taban genişliğinde, dolgu yataklı, şeffaf polikarbonat örtülü, beton kaplama tabanlı, tünel tip kurutma yatağı tasarlanmıştır. Kapalı ve açık sistem arasındaki farkı tespit etmek amacıyla aynı boyutlarda bir de açık kurutma yatağı teşkil edilmiştir. Uzun havalandırmalı kentsel bir atıksu arıtma tesisi belt filtre presinden alınan %20-25 KM içeriğindeki çamur 25 cm yüksekliğinde beton kaplama üzerine serilmiş ve kontrollü ortamda kurutma süreci incelenmiştir. Yöntemde patojen giderimini hızlandırmak amacıyla düşük miktarda (0.15 kg sönmemiş kireç / kg KM) kullanılmıştır. %23 KM içeriğindeki atık çamurun, Temmuz-Ağustos döneminde 26 gün sonunda, açık tesiste %79 KM, kapalı tesiste ise % 91 KM oranına kadar kuruduğu görülmüştür. Kasım-Aralık döneminde %23 KM içeren çamurun, 26 gün sonunda, açık sistemde hava şartları nedeniyle %17 KM’ye düştüğü, kapalı sistemde ise % 37 KM oranına kadar kuruduğu görülmüştür. Ölçümler sonunda çamur KM yüzdesi ve eklenik radyasyon değerleri arasında doğrusal bir ilişki olduğu (r2>0.9) belirlenmiştir. Buna göre belt filtre presi çıkışından alınan çamurun Katı Atıkların Kontrolü Yönetmeliği’ne göre %35 KM oranına ulaşması için 45±3 kW/m2 güneş radyasyonuna gereksinim duyulduğu hesaplanmıştır. Pilot tesisin verimi, çamur KM değişimi, kurutma süresi, patojen mikroorganizma giderimi dikkate alınarak değerlendirilmiştir. Anahtar kelimeler: Atıksu arıtma çamuru, güneşle kurutma, katı madde, fekal koliform.Sludge from biological wastewater treatment plants (WWTP) occupies a significant place in waste management, especially in recent years. Waste sludge or "biosolids" are defined as organic matter containing solid or semi-solid wastes that have been generated from wastewater treatment processes (Tchobanoglous and Burton, 1991). Sludge is a significant environmental problem because of the physical, chemical, and biological pollutants it contains. Currently, landfilling is the most common method in sludge management in our country. WWTP sludge that have been dewatered up to 20-30% dry solids (DS) content with mechanical dewatering equipment are disposed of at dumpsites or municipal landfills directly or after lime addition. Different technologies to decrease disposal costs can be applied to the WWTP sludge that can be considered as an important source with its soil enrichment capacity despite its high pathogen content. The most important parameters to be considered from the formation stage to the final disposal stage of the sludge can be given as water content, volatile solid material amount, and heavy metal and pathogen microorganism concentrations. Solar sludge drying was examined in this study. The basis for the study was to benefit from the solar energy potential of our country and increase the use of renewable energy sources. The system designed for further sludge dewatering and drying would also be used for temporary disposal. Pathogen microorganism concentration and the need for chemical material use were decreased when the system was used. First investment and operation costs of the system become more advantageous than the mechanical dewatering systems when there is sufficient space. Paved floor bed used in the system is a well known method in natural sludge drying systems. However, paved beds are not preferred in big plants because of space need, and odor and insect problems. The method became applicable with the development of sludge mixing equipments, emission control and additional heating units in recent years (Luboschik, 1999). The study was initiated to determine the disposal alternatives of the sludge that would be generated from WWTP?s of Bursa Metropolitan Municipality, which were recently put into operation. A tunnel type greenhouse with 2m x 5m paved bed floor width and transparent polycarbonate cover was designed. An open drying bed with the same dimensions was also constructed to determine the differences between the covered and open systems. Sludge was obtained from a municipal WWTP with extended aeration and spread over the concrete floor with a 25cm height. The drying process of the sludge was examined in controlled conditions. Limited quicklime (0.15 kg quicklime/kg DS) was used to speed up the pathogen microorganism removal. The performance of the pilot plants were evaluated according to the DS variations, drying time, pathogen microorganism removal rate and economical components. In 26 days in June-August period, the DS content of the sludge, which was 23% initially, increased up to 79%DS and 91%DS at open and covered plants, respectively. In November-December period initial 23%DS content of the sludge was decreased down to 17%DS in the open system, and increased up to 37%DS in the covered system, because of the weather conditions. A linear correlation (r2>0.9) was found between the DS and cumulative solar radiation. Accordingly, a solar radiation of 45±3 kW/m2 was found as a need to increase the DS content of the sludge from 20% to 35%. The faecal coliform values to determine the microorganism removal were measured according to the multiple tube method of Standard Methods. Initial coliform value of 107 Colony Forming Unit (CFU)/g.DS of the sludge with 20%DS content decreased down to U.S.Environmental Protection Agency(EPA) Class B sludge limit, which is 2.106 CFU/g.DS (USEPA, 2000) in 45 days in summer period. By adding quicklime of 0.15kg/kg.DS to the sludge, the EPA Class A sludge limit target of 103 CFU/g DS was reached in 5 days. 35% DS content target of landfilling was achieved at the end of 10 days period of time in summer. The results of the study suggested that solar drying with limited liming would be advantageous for further dewatering and/or drying purposes before the final disposal of the sludge from small and medium WWTP. Keywords: Wastewater treatment plant sludge, solar drying, dry solids, faecal coliform
