Accumulation of heavy metals by earthworms from vermicomposting
Transkrypt
Accumulation of heavy metals by earthworms from vermicomposting
Marta BOŻYM* – Faculty of Mechanical Engineering, Opole University of Technology, Opole, Poland Please cite as: CHEMIK 2014, 68, 10, 868–873 Introduction In Poland, treating of sewage sludge by earthworms was very popular in the 90’s of the twentieth-century. A pioneer in this field was a Waste-Water Treatment Plant in Pyrzyce, which began producing vermicompost for agricultural purposes [1]. Vermicomposting process is carried out in special areas, which are designed to separate vermiculture from environment, especially predators such as a mole. These areas are separated from the sides of the boards by wooden or concrete elements, while the bottom of the drainage system is located. In Poland, the most popular species for vermicomposting of sewage sludge is earthworms Eisenia fetida. In the first phase of the process, earthworms are introduced into a properly prepared stratified layer [2], which is pre-composted sludge with plant material [3, 4]. Vermicomposting of sludge takes place in stages. The precipitate is distributed in thin layers alternating with green waste (straw, hay). Consequently, there is no need to fork the compost mass, which is a routine during normal composting process in piles. Most important in the breeding of earthworms is to ensure the proper composition of the substrate, regular feeding earthworms and constant humidity. Typically, the production process of vermicompost from sewage sludge takes place from April to October. Before winter vermiculture should be specially protected with a thick layer of straw. Quality of vermicompost from sewage sludge depends on the composition of substrates, contaminants concentration or conducted treatments [2 – 4]. Under the influence of vermicomposting process improves the structure of sewage sludge, reduce the odor, dehydrates, weight decrease and increase of available forms of macronutrients content. Negative effect of this process may be an increase in heavy metal content, including mobile forms [5 – 6]. Some metals can be accumulated in the bodies of earthworms, because these animals have a high tolerance of heavy metals [6 – 10]. The aim of the study was to evaluate changes of heavy metals content in sewage sludge during vermicomposting process, examine their ability to accumulate in the bodies of earthworms and to identify factors influencing this effect. Experimental section Sewage sludges and vermicompost came from the WasteWater Treatment Plant in Lower Ligota, Opolskie Voivodeship. This Treatment Plant with a capacity of 7000 m3/d, was opened in 1999. The Treatment Plant uses a mechanical-biological treatment process, which is based on the low-convicted activated sludge chambers BIOLAK – VOX. Treated wastewater, in accordance with the permit required by Water Law Act, are discharged into the river Baryczka. Vermicomposting process of sewage sludge is used there since 1995. At the Waste-Water Treatment Plant are located five special places of vermicultures, each one measuring 100 × 3 × 0.55 m. So far vermicompost was used for agricultural purposes. Because of the complications associated with breeding Corresponding author: Marta BOŻYM – Ph.D., Eng., e-mail: [email protected] nr 10/2014 • tom 68 earthworms, the Board of Water Supply and Sewerage in Kluczbork had decided to resign from vermicomposting of sewage sludge. The samples were taken three times at monthly intervals from September to November 2012, at the end of the process of vermicomposting. Raw sewage sludge samples were collected from the dewatering press. Each vermicompost samples were collected from three vermicompost places, with a depth of about 30 cm. About 7 – 10 primary samples were taken from each vermicultures places, and then laboratory sample weighing about 0.5 kg was prepared. In addition, during the sampling of vermicompost, adult earthworms were collected (with formed clitelium). After delivery of samples to the laboratory, in sewage sludge and vermicompost a dry matter content was determined by gravimetric method at 105°C. Organic matter was determined by gravimetric method at 550°C. The rest of samples, after drying, were triturated in a mortar and sieved with a mesh size of 1 mm. After separation from the substrate, earthworms were transferred to a container of moist lignin, in order to empty the gastrointestinal tract from coprolite. Then worms were euthanased with acetone, dried, mineralized in aqua-regia and analysed. In earthworms and coprolite samples the contents of heavy metals were analysed. Sewage sludge and vermicomposts were analyzed for dry matter content and heavy metals, and also pH in 1M KCl. Heavy metals in all samples were analysed using FAAS method, after aqua regia digestion. The degree of accumulation of metals by earthworms was calculated using the formula (1): (1) where: Cumulationearthworms – the degree of accumulation of metals in earthworms relative to the nourishment (coprolite) Cearthworms – heavy metals content in earthworms bodies [mg kg-1] Ccorpolite – heavy metals content in coprolite [mg kg-1] Obtained results were statistically verified by Statistica 10 programme. Correlation coefficients (r) were calculated for the relation between concentration of metals in earthworms bodies and selected properties of sewage sludge and vermicompost samples (lenear and multivariate regression). For quality control of total metal content determination in the samples, a certified reference materials (CRM) „Sewage sludge amended soil” CRM005-050 was analysed. The recovery of metals content in CRM were respectively: Cd 96%, Pb 95%, Cu 95%, Zn 97%, Cr 95%, Ni 95%. Discussion The pH of sewage sludge and vermicompost ranged, respectively 6.70–6.85 and 6.35–6.71. Organic matter content ranged 61.2–63.5% d.m. in sewage sludge and 65.4–73.2% d.m. in vermicompost. The content of heavy metals in raw sewage sludge and vermicompost was shown in Table 1. The results were averaged for three times sampling. In addition, the results of vermicomposts samples from three special places were averaged. The results were compared with the limit values for sewage sludge applied to the land in accordance with the Polish law [11]. • 871 XV Conference Environmental Accumulation of heavy metals by earthworms from vermicomposting sewage sludges XV Conference Environmental Table 1 The content of heavy metals in raw sewage sludge and vermicompost compared with the limit values for sludge used for agricultural purposes [11] Metal Raw sewage sludge Vermicompost Limit value for agricultural use Cd [mg kg ] 1.504±0.037 2.141±0.119 20 Pb [mg kg ] 40.7±1.3 56.0±3.4 750 Cu [mg kg-1] 213±13 275±5 1000 Zn [mg kg-1] 767±10 1014±50 2500 Cr [mg kg ] 14.3±0.5 28.5±3.2 500 Ni [mg kg-1] 17.8±0.7 25.4±1.0 300 -1 -1 -1 The results were converted to dry weight, as follows: mean ± SD The content of heavy metals in sewage sludge and vermicomposts does not exceed the limit values, defined for sludge used for agricultural purposes, this allows for the natural use. The total metal content in sewage sludge was less than in vermicomposts, which occurred due to the reduction of composted sludge mass. Another reason could be the fact that storage time of vermicomposts exceeded one year and mainly the severe winter at the turn of the year 2011–2012 caused a significant reduction in the population of earthworms. The increase in the levels of few metals in vermicomposting sewage sludge was also found in a study conducted on the same Waste-Water Treatment Plant in 2000 [3]. Then the samples were taken throughout the period of vermicomposting, from spring to autumn, and the process proceeds without complications. Similar results were obtained by other authors, who reported an increase in the share of metals in the sludge during vermicomposting process [12–13]. Table 2 presents the results of heavy metals in earthworms and coprolite. In addition, given the degree of accumulation. Table 2 Content of heavy metals in earthworms (Eisenia fetida) and coprolite Earthworms Metal Coprolite The degree of accumulation of metals in earthworms relative to the nourishment Based on the obtained results, the statistical analysis was calculated, in order to determine the impact of certain parameters of vermicomposts on metals accumulation in earthworms bodies. The correlation coefficient (r) between heavy metals concentration in sewage sludge on metal content in earthworms (linear correlation) was calculated. In addition, multivariate regression analysis was performed, where the dependent variable was the content of metals in earthworms, whereas the independent variables were: metal content, pH and organic matter content (OM) in sewage sludge The results of the statistical analysis are shown in Table 3. Table 3 Statistical description of the influence of selected properties of vermicompost on the heavy metals content in the earthworms bodies Metal Coefficient of correlation* Linear and multivariate correlation equation total r=0.863 Cd(earthworm)=1.232+0.213(Cd total) total-pH-OM r=0.654 Cd(earthworm)=12.1(Cd total) +0.413(pH)+0.070(OM)+0.614 total r=0.143 Pb(earthworm)=48.05+0.26(Pb total) total-pH-OM r=0.695 Pb(earthworm)=2.730(Pb total)34.2(pH)+2.57(OM)+67.5 Cd Pb Cu total r=-0.480 Cu(earthworm)=376-0.753(Cu total) total-pH-OM r=0.519 Cu(earthworm)=0.890(Cu total)+16.7(pH) -1.12(OM)+99.2 total r=0.769 Zn(earthworm)=261.9+0.738(Zn total) total-pH-OM r=0.463 Zn(earthworm)=1.70(Zn total) -12.2(pH)+35.6(OM)-1642 total r=-0.490 Cr(earthworm)=36.9-0.419(Cr total) total-pH-OM r=0.831 Cr(earthworm)=18.6(Cr total)+ -3.5(pH)+1.15(OM)-46.8 Zn Cr Cd [mg kg-1] 4.27±0.49 2.12±0.24 2.01 Pb [mg kg-1] 30.7±1.9 56.8±3.2 0.54 Cu [mg kg ] 134±3 278±3.1 0.48 total r=0.917 Ni(earthworm)=7.226+10.607(Ni total) Zn [mg kg-1] 1019±54 980±55 1.04 total-pH-OM r=0.727 Cr [mg kg-1] 2.00±0.28 29.2±3.1 0.07 Ni(earthworm)=-1.60(Ni total)4.3(pH)+0.27(OM)+13.5 Ni [mg kg ] 27.6±1.1 25.0±1.4 1.11 -1 -1 The content of cadmium in the bodies of earthworms was twice higher than the sewage sludge (accumulation ratio = 2.01) (Tab. 2). The content of zinc and nickel was at a similar level as in coprolite (accumulation ratio = 1.04 and 1.11). In contrast, no increased accumulation of lead and copper in the bodies of earthworms was observed. The contents of these metals was twice lower than in coprolite (accumulation ratio = 0.54 and 0.48). The degree of accumulation of chromium was very low, as indicated by the capacity for accumulate this metal in earthworms bodies (accumulation ratio =0.07). Otherwise has been the case in previous studies, which were carried out on that Treatment Plant, the capacity to accumulate certain metals by earthworms was observed [3]. In later studies it was found that the ability of accumulation of metals depends on the phase of development of earthworms. The highest concentration of metals was determined in adults (with clitellum) [4]. 872 • Ni * – r – linear and multivariate correlation coefficient Nickel (r=0.917), cadmium (r=0.863) and zinc (r=0.769) contents were correlated positively with this metals content in earthworms bodies. In the case of these metals, no additional effect of pH and the content of organic matter (OM) deposits. In contrast, the content of lead and chromium, also affect the pH and organic matter of sewage sludge on the accumulation of metals in the bodies of earthworms. For these metals, taking into account the three parameters (metal content, organic matter and pH), an increase of the correlation coefficient values was observed (Tab. 3). Other authors also confirmed a direct impact of pH and organic matter content on the accumulation of metals by earthworms [14–15]. Another factor affecting the degree of accumulation of metals in the body of earthworms can be interaction of various metals in sewage sludge, for example, Pb, Cd, Zn, and Cu [7]. Accumulation of copper in the bodies of earthworms dependent slightly on the content in sewage sludge (r=0.480–0.519). nr 10/2014 • tom 68 2. 3. 4. 5. 6. 7. 8. 10. 11. 12. Literature 1. 9. Kostecka J.: Kompostowanie z udziałem dżdżownic – nowe możliwości, Materiały I Konferencji Naukowo Technicznej „Kompostowanie i użytkowanie kompostu, Puławy-Warszawa, 16-18.06.1999, 125-131. Kostecka J.: Uzdatnianie osadów ściekowych w wermikulturze., Materiały II Konferencji Naukowo Technicznej „Przyrodnicze użytkowanie osadów ściekowych”, Puławy-Lublin-Jeziórko 26-28.05.1997, 171-176. Bożym M.: Zmiany parametrów fizykochemicznych osadu ściekowego w czasie wermikompostowania, Zeszyty Problemowe Postępów Nauk Rolniczych, 498, 2004, 33–39. 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Spurgeon D.J., Hopkin S.P., Jones D.T.: Effects of cadmium, copper, lead and zinc on growth, reproduction and survival of the earthworm Eisenia fetida (Sav.): assessing the environmental impact of point-sousce metal contamination in terrestrial ecosystems. Environmental Pollution, 84, 1994, 123-130. 13. 14. 15. Kalembasa D.: Wpływ stężenia Cd, Pb i Ni w podłożu na biomasę i rozrodczość dżdżownicy Eisenia fetida, Zeszyty Naukowe AR w Krakowie, 334 (58), 1998, 121-124. Neuhauser E.F., Loehr R.C., Milligan D.L., Malecki M.R.: Toxicity of metals to the earthworm Eisenia fetida. Biology and Fertility of Soils, 1, 1985, 149-152. Rozporządzenie Ministra Środowiska z dnia 13 lipca 2010 r. w sprawie komunalnych osadów ściekowych (Dz. U. 2010, nr 137, poz. 924). Patorczyk-Pytlik B., Spiak Z., Rabikowska B.: Ocena wartości nawozowej obornika i osadu sciekowego przetworzonego przez dżdżownice w drugim roku po zastosowaniu, Zeszyty Naukowe Postępów Nauk Rolniczych, 409, 1993, 143-150. Zabłocki Z., Kiepas-Kokot A., Zmiany niektórych właściwości chemicznych komunalnych osadów ściekowych w procesach: kompostowania i wermikompostowania, Zeszyty Naukowe AR w Krakowie, 58, 1998, 101-108. Spurgeon D.J. i Hopkin S.P.: Effect of variations of the organic matter content and pH of soils on the availability and toxicity of zinc to the earthworm Eisenia fetida., Pedobiologia, 40, 1996, 80-96. Beyer W.N., Hensler B., Moore J.: Relation of pH and other soil variables to concentrations of Pb, Cu, Zn, Cd, and Se in earthworms. Pedobiologia, 30, 1987, 167-172. *Marta BOŻYM – Ph.D., Eng., completed a M.Sc. degree in chemistry, is a graduate of the Faculty of Mathematics, Physics and Chemistry, Opole University (1998). Additionally, in 2005, she got a B.Sc. degree in environmental engineering, is a graduate of the Faculty of Mechanical Engineering, Opole University of Technology. Ph.D. thesis defended at Wrocław University of Environmental and Life Sciences (2006). Currently she works at the Faculty of Mechanical Engineering at Opole University of Technology. Research interests: migration of heavy metals in the environment, development of municipal and industrial waste, the use of sewage sludge. She is the author of over 50 scientific articles and author or co-author over 50 papers and posters at national and international conferences. e-mail: [email protected], phone: +48 77 449 8381 Z prasy światowej – innowacje: odkrycia, produkty i technologie From the world press - innovation: discoveries, products and technologies Największa na świecie pływająca elektrownia fotowoltaiczna powstanie w 2015 r. W Japonii zostanie wybudowana największa na świecie pływająca elektrownia fotowoltaiczna. Panele fotowoltaiczne będą zainstalowane na wodzie dzięki specjalnym systemom montażowym, wykonanym z tworzyw o dużej gęstości, odpornych na działanie promieniowania UV, korozję i całkowicie recyklowalnych. Systemy tego rodzaju są stosowane we Francji od ponad trzech lat, i okazały się wytrzymałe nawet na ekstremalne warunki środowiskowe. Co więcej, woda w zbiornikach wodnych w naturalny sposób chłodzi instalację, dzięki czemu będzie ona bardziej wydajna niż panele słoneczne mocowane na dachach. Docelowo pływająca elektrownia słoneczna będzie miała łączną moc 2,9 MW. Instalacje zostaną umieszczone na dwóch jeziorach znajdujących się w pobliżu miejscowości Kato, koło Osaki. Pomysł umieszczenia instalacji solarnych na wodzie został podyktowany wysokimi cenami gruntów w Japonii. Zakończenie budowy instalacji rozpoczętej we wrześniu br. jest przewidziana na kwiecień 2015 r. (kk) (http://www.plasticseurope.pl, 30.09.2014) nr 10/2014 • tom 68 Cenny materiał dla energetyki wiatrowej Starania o uniezależnienie się od energii jądrowej i paliw kopalnych, które podejmują Niemcy, mają miejsce w wielu krajach na całym świecie. Za jedno z najbardziej ekologicznych źródeł energii uważa się energię wiatru. Szczególnie w przypadku dużych turbin, inżynierowie często wybierają produkt o nazwie Levapren, dostarczany przez koncern LANXESS, będący producentem specjalistycznych środków chemicznych. Powodem tego jest fakt, iż ten bezhalogenowy, syntetyczny kauczuk etyleno-winylo-octanowy (EVM) pomaga znacząco zmniejszyć ryzyko pożaru w pobliżu prądnic oraz zabezpieczyć duże inwestycje w przypadku pożaru. Ponadto osłony kablowe wykonane z materiału Levapren mają dodatkowe, bardzo pożądane właściwości: Levapren jest łatwy w obróbce. Wersje biegunowe tego materiału, tj. Levapren 500 i Levapren 700, prawie wcale nie pęcznieją w oleju, co także jest istotne, ponieważ wchłonięty olej mógłby osłabić właściwości kabli w przypadku pożaru i zwiększyć gęstość dymu. (kk) (LANXESS, 15.09.2014) Dokończenie na stronie 881 • 873 XV Conference Environmental Conclusions The results confirmed that during the vermicomposting process of sludge increased heavy metal content. This is due to reducing the mass of treated sludge. The metal content in the earthworms bodies was higher than in sewage sludge and vermicomost. Metal accumulation by earthworms affected the total content of heavy metals in sewage sludge, pH and organic matter content.