Aerobic Granulation in a Sequencing Batch Reactor for the Treatment of Piggery Wastewater

Aerobic Granulation in a Sequencing Batch Reactor for the Treatment of Piggery Wastewater Dalei Zhang1*, Yanan Wang1, Hongwei Li1, Shaoran Wang2, Yumei Jing3 ABSTRACT: This study investigated the formation of aerobic granules strategy on the treatment of swine wastewater and found that fed with digested piggery wastewater. After 42 days of cultivation, small feeding ratio had a more significant effect on the removal of yellow granules with mean diameter of 0.4 mm were first observed in the phosphorus and nitrogen than on the removal of chemical reactor. Scanning electron microscope pictures showed the granules oxygen demand (COD). Huang et al. (2011) found that high were compact, round structures with clear outer shapes and mainly 2þ 2þ composed of filamentous bacteria. Maximum chemical oxygen demand concentrations of K and Ca would be helpful for removing and ammonia removal ratios were 90.1 and 91.7%, respectively. The nutrients in piggery wastewater. Previous studies have shown Monod equation, which was used to describe ammonium utilization, great improvements in treating piggery wastewater, but there are yielded a maximum rate of 6.25 mg (g volatile suspended solids)À1 hÀ1. still some problems that hinder treatment (Latif et al., 2011). The measurement of extracellular polymeric substances (EPS) content Rich nitrogenous compounds in the wastewater make active and three-dimensional excitation and emission matrix results showed biomass densification, granular processes, and, consequently, that the EPS concentration increased during the granulation process. microorganism retention in the reactor difficult, limiting the use Fluorescence in situ hybridization analysis showed significant amounts of upflow anaerobic sludge blanket (UASB) reactors. of nitrifying bacteria in the aerobic granules. Results in this study provide insights to the treatment of piggery wastewater using aerobic granular Because of its promise for biological wastewater treatment, sludge. Water Environ. Res., 85, 239 (2013). immobilized-bacteria technology has been extensively investigated (Adav et al., 2008a; Choi et al., 2011; Kim et al., 2011). KEYWORDS: aerobic granules, piggery wastewater, sequencing batch Compared with conventional activated sludge, aerobic granules reactors, nitrogen removal, fluorescence in situ hybridization. have good settling properties, dense microbial structure, high doi:10.2175/106143012X13560205145136 biomass concentration, and good capacity to deal with toxic media (Adav, Lee, Show, and Tay, 2008; Su and Yu, 2005). Taking advantage of individual granule properties, aerobic granules were used to treat high-strength wastewaters containing Introduction organics, nitrogen, phosphorus, and toxic substances (Moussavi Livestock and poultry breeding have developed rapidly in et al., 2010; Shi et al., 2010; Winkler et al., 2011). Considerable China in recent years. However, this rapid development has research has been carried out on nitrogen removal by aerobic caused difficult environmental pollution issues. Large quantities granules, and because of the good results obtained, aerobic of wastewater containing ammonium, phosphorus, and organic granulation seems to be a suitable process for treating piggery matter have been discharged to the environment, causing wastewater. However, aerobic granules have not yet been applied serious environmental problems such as eutrophication in lakes in the treatment of piggery wastewater, and there is still a lack of and rivers. As is typical of livestock and poultry breeding knowledge about aerobic granulation processes fed with piggery wastewater, piggery wastewater is considered to have a drastic wastewater. effect on the environment and human health, as it contains high The main purpose of the present study, therefore, was to concentrations of nitrogen, phosphorous, and organic matter investigate the feasibility of cultivating aerobic granules using (Han et al., 2011). piggery wastewater in a sequencing batch reactor (SBR). The Many researchers have sought solutions for treating piggery formation process, physicochemical parameters, activities, and wastewater (Han et al., 2011; Xu & Shen, 2011). Zhang et al. microbial community of aerobic granules were investigated in (2011) studied anaerobic codigestion of piggery wastewater and food waste and identified the key factors governing codigestion this work. The information provided is useful for understanding performance. Han et al. (2011) investigated the effect of feeding the mechanism of aerobic granulation, as well as its future application in the treatment of piggery wastewater. 1 School of Environmental and Municipal Engineering, Qingdao Materials and Methods Technological University, Qingdao 266033, China. Inoculated Sludge and Wastewater Content. The reactor 2 Qingdao Research Academy of Environment Science, Qingdao, 266000, China. was inoculated with 2.0 L of sludge from the Qingdao Municipal Wastewater Treatment Plant located in Shandong, China. The 3 Sewage Wastewater Treatment Plant of Haibohe, Qingdao, 266000, China. sludge contained mixed liquor suspended solids (MLSS) of 2.8 g/ L, mixed liquor volatile suspended solids (MLVSS) of 1.82 g/L, a * School of Environmental and Municipal Engineering, Qingdao Technological University, Qingdao 266033, China; e-mail: MLVSS/MLSS ratio of 0.65, and a sludge volume index (SVI) of [email protected]. 73.46 mL/g. March 2013 239 Zhang et al. Table 1—Characteristics of the digested wastewater. HM 550, Thermo Fisher Scientific, Kalamazoo, Michigan) and mounted on gelatin-coated glass slides. After air drying at room Parametersa Digested wastewater temperature, hybridization was conducted following the method CODt (g/L) 53.5 6 2.3 described by Sekiguchi (1999). CODs (g/L) 6.9 6 1.4 A carboxy-X-rhodamine (ROX) labeled Nso190 probe þ NH4 -N (g/L) 4.3 6 1.0 (50CGATCCCCTGCTTTTCTCC30) targeting ammonia-oxi- SS (g/kg) 38.7 6 2.4 dizing bacteria (AOB) and a fluorescein isothiocyanate (FITC) pH 8.0 6 0.3 labeled NIT3 probe (50CCTGTGCTCCATGCTCCG30) target- a þ CODt ¼ total COD, CODs ¼ soluble COD, NH4 -N ¼ ammonium nitrogen, ing nitrite-oxidizing bacteria (NOB) were used. Hybridized and SS ¼ suspended solids. samples were viewed with a fluorescence microscope (DM6000 B, Leica Microsystems, Wetzlar, Germany). Digital images were Undiluted, digested piggery wastewater was collected from a analyzed using Image Pro Plus (version 6.0, Media Cybernetics, methane tank of a pig farm in Qingdao, China. The main Inc., Rockville, Maryland). Three samples were measured to characteristics of the digested wastewater are presented in Table determine average values, and at least 10 different fields were 1. The digested wastewater was centrifuged at 8000 rpm for 1 examined for each sample. hour to eliminate suspended matter and then was diluted and Analysis. The COD, MLSS, MLVSS, SVI, ammonium, nitrate, used as influent to the SBR. The organic loading rate (OLR) was and nitrite concentrations were measured according to Standard 6.9 to 7.2 kg COD mÀ3 dÀ1, and the influent nitrogen Methods (APHA et al., 1998). The pH was measured with a concentration was 120 to 160 mg/L. Some other necessary digital, portable pH meter. Extracellular polymeric substances trace elements were added to ensure the growth of bacteria (Shi (EPS) were extracted by cation exchange resin according to the et al., 2010). The pH of the diluted wastewater was 7.5 6 0.1. method developed by Frolund et al. (1996). Protein (PN) was Reactor Set-Up and Operation. The experiments were measured by the Lowry method (modified) with bovine serum performed in an SBR with a working volume of 4.0 L, internal albumin as standard, and polysaccharide (PS) content was diameter of 70 mm, and height of 1200 mm. Air was introduced analyzed by the anthrone method with glucose as standard through a diffuser by pump; superficial upflow air velocity was (Frolund et al., 1996; Lowry, 1956). The granule structure and 14 mm/s. The dissolved oxygen concentration was 4.8 mg/L. surface morphology were viewed via an SEM (Quanta 200 FEG, The reactor was operated at room temperature (25 6 28C). FEI Company, Hillsboro, Oregon). The reactor was operated sequentially in a 4-hour cycle, including a filling time of 8 minutes, aeration of 224 minutes, Results and Discussion settling of 6 minutes, and effluent withdrawal of 2 minutes. The Formation and Physical Characteristics of Aerobic Gran- settling time of the reactor was decreased from 6 minutes to 2 ules. The initial seeding sludge had a fluffy and irregular minutes on day 30, as a shorter settling time was beneficial to structure as is typical of flocculent activated sludge. As shown in granule formation (Adav et al., 2009). The volumetric exchange Figure 1, sludge properties changed during the granulation ratio was 50%, and the hydraulic retention time (HRT) was 8 process: Settling properties gradually improved, and MLSS hours. increased with cultivated time, consistent with previous studies Three-Dimensional Excitation and Emission Matrix Fluo- (Ma et al., 2011; Su and Yu, 2005). There was not much sludge rescence Spectroscopy. Three-dimensional excitation and washed out from the reactor as reported by others, probably emission matrix (EEM) spectra are a series of emission spectra because a settling time of 6 minutes was used in the initial 30 over a range of excitation wavelengths, and they can be used to days. Settling time was decreased from 6 minutes to 2 minutes identify fluorescent compounds present in complex mixtures. on the

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