Tavuk Atıklarının Farklı Aşı Çamuru İçeren Yukarı Akışlı Havasız Çamur Yataklı Reaktörlerde Arıtılabilirliğinin Karşılaştırmalı Olarak Değerlendirilmesi

Abstract

Hayvan atıkları içerisinde önemli bir yere sahip olan kümes hayvanlarından (tavuk, ördek, hindi vb.) kaynaklanan atıklar, son yıllarda önemi hızla artan çevresel problemler arasında yer almaktadır. Beyaz et tüketiminin, tüm gelişmiş ve gelişmekte olan ülkelerde olduğu gibi, ülkemizde de son yıllardaki hızlı artışı; hayvancılık sektöründe büyük oranda et ve yumurta işletmelerinin çoğalmasına neden olmuş ve bu durum ülkemizde, kümes hayvanlarından kaynaklanan atıkların önemli oranda artmasına sebep olmuştur. Bu tez çalışmasında, yumurtacı tavuk çiftliklerinden kaynaklanan hayvansal atıkların; farklı aşı çamuru (granüler ve floklu) içeren, aynı işletme koşullarında ve oda sıcaklığında çalıştırılan iki adet yukarı akışlı Havasız Çamur Yataklı Reaktör’de (HÇYR), anaerobik arıtılabilirliği karşılaştırmalı olarak incelenmiştir. Her iki reaktör, günlük olarak (1+6) oranında seyreltilmiş tavuk atığı ile beslenmiştir (HBS=13 gün). Her iki reaktörde oluşan gaz miktarları ile reaktörlerdeki giderim performansları konvansiyonel parametreler yardımıyla değerlendirilerek, HÇYR’lerde gerçekleşen havasız arıtma performansları birbirleriyle karşılaştırılmıştır. Böylece, yumurtacı tavuk atıklarının HÇYR’lerde gerçekleşen arıtımı açısından hangi aşı tipinin (granüler ya da floklu) daha uygun olduğu da ortaya konulmuştur. Birinci bölümde, çalışmanın esasları ve önemi hakkında bilgiler verilmiştir. İkinci bölümde ise, havasız arıtmanın esasları açıklanmıştır. Ayrıca, havasız arıtmaya etki eden faktörler ile havasız arıtmada kullanılan sistemler de kısaca anlatılmıştır. Bu bölümde ayrıca çalışmada kullanılan HÇYR sistemleri hakkında detaylı bilgi verilmiştir. Üçüncü bölümde, hayvansal atıkların havasız arıtılabilirliği incelenmiştir. Bu amaçla, hayvansal atıklarla ilgili literatür araştırılarak; özellikle tavuk atıklarının genel özellikleri ve havasız arıtılmaları ile ilgili bilgiler verilmiştir. Ayrıca, benzer konuda yapılmış çalışmalar da kısaca incelenmiştir. Dördüncü bölümde, çalışmada kullanılan tavuk atığı ve reaktörlere beslenen substratın (1+6 oranında seyreltilmiş tavuk atığı) karakterizasyonu, işletilen HÇYR’ler ile çalışmada kullanılan aşı tiplerinin genel özellikleri, reaktörlerin işletme koşulları, yapılan deneylerde kullanılan ekipmanlar ve analitik yöntemler hakkında bilgi verilmiştir. Son bölümde, granüler ve floklu aşı çamuru içeren reaktörlere beslenen substrattan ve her iki reaktörün besleme sonrası çıkış sularından alınan numunelerde yapılan deneylere ait sonuçlar konvansiyonel kirletici parametreler esas alınarak incelenmiştir. Ayrıca günlük olarak ölçülen sıcaklık değerleri ve gaz üretimleri de bu bölümde verilmiştir. Farklı aşı içeren HÇYR’lerden elde edilen sonuçlar karşılaştırılarak çizelge halinde sunulmuştur. Çalışma sonucunda, doğal ortam sıcaklığında (herhangi bir ilave ısıtma uygulanmaksızın) işletilen her iki HÇYR’de gerçekleşen biyogaz üretimleri giderilen TKOİ, UAKM ve UKM parametreleri açısından karşılaştırılmıştır. Buna göre, granüler aşı çamuru içeren reaktörde üretilen biyogaz miktarları sırasıyla 0,07 L/gTKOİgid, 0,11 L/gUAKMgid ve 0,09 L/gUKMgid olarak bulunmuştur. Floklu aşı çamuru içeren reaktörde ise bu değerler sırasıyla, 0,04 L/gTKOİgid, 0,06 L/gUAKMgid ve 0,05 L/gUKMgid olarak hesaplanmıştır. Böylece, aynı şartlarda işletilen reaktörlerde, granüler aşı çamuru içeren reaktördeki biyogaz üretim veriminin, floklu çamur içeren reaktörde gerçekleşen biyogaz üretim verimine kıyasla daha yüksek olduğu gözlenmiştir.

In recent years, in parallel with inevitable increases inpopulation as well as in the consumption of the natural resources, one of the most significant challenges encountered in many countries is how the produced wastes are going to be disposed of in an environmentally sustainable and a safe manner. Current and potential environmental problems associated with livestock farming are a major concern in many areas of the world. Excess nutrient is formed during livestock farming operations; this may lead to nutrient accumulation in the soil and undesirable nutrient discharges to the environment. Because livestock farming is very important for the agricultural economy and as a food source, management practices that will achieve sustainable livestock farming and appropriate environmental protection are needed. Anaerobic digestion of organic wastes is considered as one of the most appropriate treatment alternatives due to biogas and nutrient recovery. Anaerobic digestion is applied worldwide for the treatment of industrial, agricultural and municipal wastes. It involves degredation and stabilisation of the organic material under anaerobic conditions by microbial organisms and leads to the formation of methane and inorganic products including carbon dioxide. In the world, animal wastes have been treated by anaerobic reactors in order to obtain biogas for many years. When the animal wastes are solely treated anaerobically, methane production might be observed in the range of 10-20 m3 CH4/ton. Anaerobic digestion is also a relatively efficient conversion process for poultry litter, producing a collectable biogas mixture with an average methane content of about 60%. In Turkey, if the numbers of cattle, sheep and poultry, are considered approximately as 13, 30 and 265 million, respectively; respective annual waste capacity is estimated around 128, 25, and8 million tons. According to this, annual amounts of total solids (TS) are 16.2, 6.1 and 1.9 million tons. If 0,150 m3 of methane is assumed to be converted per kg of TS, approximately 1,87 billion m3 methane generation could be calculated annually. Accordingly, the potential of annual energy recovery (if 60% recovery is assumed), could be calculated as ca. 5.43 million MW-hr which corresponds to about 620 MW energy capacity. Poultry are produced daily the feces of 3 to 4% by body weight. On the average, the rate of one bird excreta was adopted a 22 kg/year into the poultry house. Approximately 7 million tones of poultry feces creates environmental problems in Turkey. On the other hand, poultry sector suffering from seven million tons of waste. Since animal wastes contain high ammonia concentrations, these wastes have high buffering capacities. Besides, animal wastes have lower TS contents than the organic fraction of municipal solid wastes (3-5% for the piggery wastes and 6-9% for the cattle wastes). Animal wastes are richin nutrients which are required for microbiological growth, their agricultural fertilizer value is very high. Poultry wastes (chicken, duck, turkey etc.) are considered among the significant environmental problems in recent years. Recently, the rapid increase in white meat consumption in our country, as in all developed countries, results in rapid growth of livestock enterprises producing meat and eggs. As a result of the growing poultry industry, poultry slaughterhouses and egg producers are generating increasing amounts of organic solid by-products and wastes. On the other hand, legislation on the recovery of organic materials for animal feed is becoming tighter and more restrictive of their landfilling. In this regard, anaerobic digestion is a promising alternative for the treatment of these materials, as the process combines material recovery and energy production. Waste from the poultry industry includes a mixture of excreta (manure), bedding material or litter (e.g. wood shavings or straw), waste feed, dead birds, broken eggs and feathers removed from poultry houses. Other wastes include those from cage, conveyer belt and water-flushing systems. The litter and manure component of this waste has a high nutritional value and is used as an organic fertiliser. This waste of manure contains the major plant nutrients of nitrogen (N), phosphorus (P), and potassium (K). The amounts of these nutrients can vary depending upon many factors including the age and diet of the flock, as well as the moisture content and age of the manure. Poultry manure also contains the secondary plant nutrients such as zinc, copper, boron, iron, and manganese. Poultry manure containing large quantities of calcium carbonate can improve acidic soils for crop production. Poultry manure contains significant concentrations of organic nitrogen due to the presence of high levels of protein and amino acids. Of the nitrogen in fresh manure, 60-80% is typically in organic form, such as urea and protein. Depending on the environmental conditions, a large percentage of this organic nitrogen (40-90%) is converted into ammonia within a year. During anaerobic digestion of poultry manure, the concentration of endogenous ammonia-nitrogen rises considerably. Although some members of the anaerobic microorganism population can use ammonium ions, an excess of ammonium can inhibit the destruction of the organic compounds as well as the productions of the volatile fatty acids and the methane gas. The presence of ammonium ions also contributes to a corrosively high pH and leads to handling, storage and disposal problems. Hence, decreasing the ammonia content is desirable for an effectivetreatment of the poultry litter. In this study, anaerobic treatability of chicken (laying hen) manure was evaluated comparatively in two identical Up-flow Anaerobic Sludge Bed (UASB) reactors inoculated with different sludge sources (flocculent and granular). Both reactors, having similar operating conditions, have been operated at ambient temperature without any heating requirement, hydraulic retention time is 13 days and both reactors have been fed with same substrate (chicken manure diluted with tap water in ratio of 1+6) on daily basis. The treatment performances of both reactors are compared to each other, with the assessment of biogas production and chemical oxygen demand (COD) removal. Thus, which inoculation type might be more appropriate for the biogas production and the anaerobic treatment of chicken (laying hen) manure. In the first part, principles and the significance of this study are given. In the second part, the fundamentals of anaerobic treatment is examined. Besides, the parameters affecting anaerobic treatment and the anaerobic treatment systems are given briefly. The UASB reactors is explained in detail. In the third part, the anaerobic treatment of livestock manure is examined. For this purpose, the technical literature is reviewed. Especially, the general features of chicken manure and the anaerobic treatability of chicken manure are given in detail. In addition, the studies on disposal chicken manure with biological treatment systems is examined in brief. In the fourth part, chicken manure and the substrate (1+6) characteristics, UASB characteristics used in this study, the inoculation characteristics, operating conditions, the equipments and the analytical methods are given. In the last part, experimental results from both reactors are shown. The experimental results of TCOD, SCOD, TKN, NH3-N, SS, VSS, alkalinity, pH parameters are given and compared for both reactors. Aditionally, daily measured temperature and biogas production results are also given and compared in a table in this chapter. Results are shown as biogas productions respectively per total COD, VSS and VS in both reactors. In the UASB reactor inoculated with the granular sludge, the biogas productions per removal are 0.07 L/gCOD, 0.11 L/gVSS and 0.09 L/gVS. In the UASB reactor inoculated with the flocculent sludge, the biogas productions per removal are 0.04 L/gCOD, 0.06 L/gVSS and 0.05 L/gVS. Consequently, it has been observed that the biogas production yields in the UASB reactor inoculated with the granular sludge are higher than the biogas production yields in the UASB reactor inoculated with the flocculent sludge. According to the results, average TCOD removal efficiency in the UASB reactor inoculated with the granular sludge is about 95% whereas average TCOD removal efficiency in the UASB reactor inoculated with the flocculent sludge is about 91%. On the other hand, average SCOD removal efficiencies in the UASB reactors inoculated with the granular and the flocculent sludges are about 82% and 72%, respectively. According to TSS and VSS removal efficiencies, similar results are observed in both reactors. However, cumulative biogas production in the UASB reactor inoculated with the granular sludge is 2.5 times higher than the UASB reactor inoculated with the flocculent sludge during the study. Moreover, average biogas yield per gram TCOD removal in the UASB reactor inoculated with the granular sludge is approximately 1.75 times higher than the UASB reactor inoculated with the flocculent sludge. Hence, anaerobic treatment is an appropriate alternative for the reduction of the environmental pollution caused by chicken manure in Turkey, and the UASB reactors operated at ambient temperatures could be realized with less operating costs. Moreover, by comparing the treatment performances of two UASB reactors including different seed sludges; it was also investigated that the granular seed is more appropriate for the laying hen manure. With this study, decrease in the problems encountered during laying hen manure disposal could be studied with the biogas recovery potential as the renewable energy source.