Preliminary of Serial Self- turning reactor (STR) to sewage sludge composting

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1 00 International Conference on Biology, Environment and Chemistry IPCBEE vol. (0) (0) IACSIT Press, Singapore Preliminary of Serial Self turning reactor (STR) to sewage sludge composting Wachcharadej Boonlualohr Department of Civil Engineering and Technology Sirindhorn International Institute of Technology Thammasat University Patumthani, Thailand Taweeep Chaisomphob Department of Civil Engineering and Technology Sirindhorn International Institute of Technology Thammasat University Patumthani, Thailand AbstractThis article is an action research branched from the Jointresearch Project on Composting Technology : JPCT. The objective of the study is to applying the new composting technology Serial Selfturning Reactor System : STR which are originally developed for Municiple Solid Waste (MSW) treatment to be used for sewage sludge from the wastewater treatment plant. A series of LabScaled and plantscaled experiments are performed. The result leads to a new conditions setting. At the end of study, found that the proportions of ::0. and ::0. are the most suitable mixing proportion for sewage sludge composting by using STR technology. KeywordsBioMYBOX, Aerated bio reactor, Sewage sludge treatment, Composting I. INTRODUCTION Wastewater sludge from waste water treatment plant is a one problem in waste disposal for small and medium communities due to the physical characteristic of the waste itself are disgusting, and odor. Many communities use an airdried or compost methods but these methods still have a problem with the odor in the surrounding areas and some of the communities are dispose sludge by dumping with other waste which considered as unsuitable way; therefore, composting is an appropriate alternative for waste management (Kanat et al., 006) []. Composting not only helps to solve the problem of waste disposal, but also produces a useful bioamendment agent (compost) (Banegas et al., 007) []. Sewage sludge from municipal treatment plants are good candidates for composting and for agricultural purpose (Akhtar and Malik, 000) [], but there are many factors that affect the composting process, such as the proportions of the mixture, the aeration rate, oxygen consumption rates, composting recycling, moisture content, ph and C/N, and so on (Golueke and Diaz, 996) [] Thammasat University (TU) Rangsit campus has been innovated and developed the organic wastes disposal system so called Serial Selfturning Reactor SystemSTR as an organic preliminary MSW treatment system since 00. Because wastewater sludge is one of the MSW which considered as an organic wastes, it leads us to study the possibly of sewage sludge composting with STR and extend the applications of STR to reduce cost of waste disposal and become a concept technology for other communities and local administration to applied this technology for using within the communities according to the local decentralize plan in Thailand constitution year 007, which considered as the wastewater treatment and sludge disposal are one of the public utility that government must provide for citizen and devolve the responsibility to the local administration soon. II. MATERIALS AND METHODS This research aims to applying the STR technology with the wastewater sludge treatment. The methods and materials that use in this research comprise of A. STR Composting Method Technology The serial selfturning reactor (STR), the system consists of vertically aerationtype reactors and sets of selfturning units. These two types of units are connected vertically making a series of composting and turning processes in alternate sequence. The reactor is assembled by several vertical reactor clusters for adjusting the total reactor capacity. It contains vertical aeration through perforated pipes and odor venting passage. Reactor doors mechanism located at the bottom of each reactor is installed as for controlling the composted mass flowing through the self turning units below. The doors are able to be closed and opened to adjust the period of composting in the reactor. The selfturning units are next below the reactor unit called My Box. It contains no mechanical hardware but only complicated passages to direct flows of different types of material while falling down and impacting the unit walls due to earth gravity, which then resulted in mixing process of the loaded material. Mixture of compost material will firstly be loaded in the topmost reactor. After composting period in the reactor is over, the composted mass will be passed to the adjacent selfturning unit and then next reactor below in consequential order. After the compost mass has passed all the unit sequences, compost product will be obtained. The selfturning reactor (STR) unit in the prototype system contains reactor fermentation and a parallel turning unit (using BioMYBOX). Its function is fermentation of input compost mass from the top. The reactor is aerated by a number of vertical compressed air dispensers. Supplying compressed air using vertical dispenser ensures low possibility in clogging of the air holes, which can much reduce maintenance cost. After 7

2 one batch of fermentation, fermented mass will be passed out to the next unit below by using only self weight (gravitational force) (Bongochgetsakul, 006) []. Cu (mg/kg) Hg (mg/kg) Pb (mg/kg) Garbage, Reactor MYBOX Liftin g Figure. Showing the design and working concept of STR technology. B. Composting materials Sewage sludge (SS) from Chatuchak wastewater treatment plant in Bangkok administration was used in this study. SS that was collected has a physical characteristic similar to a soil with an odor and contain a lot of moisture so we have to reduce the moisture content by using airdried method before using it. The woodchip (WC) that use in this study as a bulking agent came from a shredded scarps of routine landscape work of TU. Recycled composts (RC) were used as one of the composting amendment bulking agent to reduce the amount of WC using in compost pile. Another reason that we have to use RC in our pile compost because of SS contains no activated bacteria but RC has one, therefore, the different of varied proportions with amendments bulking agent were performed in this study. The main characteristic of SS and WC are shown in table I. TABLE I. CHARACTERISTIC OF THE COMPOSTING MATERIALS Parameter Sewage sludge Woodchip Organic matter (OM), Organic carbon Moisture content Density ph C/N ratio Electric conductivity (EC) N P K As (mg/kg) Cd (mg/kg) Cr (mg/kg) Liftin g Composting Composting C. Composting method In order to perform the STR composting, the necessary labscaled experiments were performed to identify the degradation of composting of each proportion. Then, the STR composting will be performed after analysis of labscaled degradation by using the same condition of labscaled composting to compost with it. Therefore, the different proportion of SS, WC, and RC were mixed for labscaled composting. From a study of the composting of dairy manure with rice straw, Li et al. (008) [6] reported that an aeration rate of 0.L/min kg VS was capable of achieving the highest composting temperature. Then, we decided to use a forced aeration rate of 0. L/min kg VS in each case. The composting of labscaled were performed in the galvanized steel box meter insulated with foam in each surface except on the top surface. Each box has an air supply tube attached with flow gate and regulator for a constant flow rate air supplying inside of the composting box through air horse from an air compressor. The proportions and conditions of labscaled composting are shown in table II. The composting experiments included groups (Table II). The mixture of SS, WC, and RC were composted in the first three experiments by varying the mix proportion of two types of amendment (bulking agent) and one type of substrate to find appropriate proportions of the mixture under continuous aeration at 0.L/minkg VS. In experiment, two ratios of SS and RC (:0. and :0., v:v) were applied to study the influence of using RC as only one amendment (bulking agent). TABLE II. PROPORTIONS AND CONDITIONS OF LABSCALED COMPOSTING SS: WC:RC (v: v: v) Aeration rate (L/min kg VS) Initial moisture Turning requirement Composting duration.):0.:0.):0.: 0..):0.:0..):0.:.):0.:0 6.):0.:0. 7.):0.:0. 8.):0.: 9.)::0 0.)::0..)::0..):: % days % days % days.):0:0..):0:0. % days D. Sampling and analyses Samples were taken at the mature compost stage after curing and sieving for the analysis of organic matter, C/N ratio, N, P, K, ph, electrical conductivity (EC), and moisture content 76

3 (MC) by sending the samples to Office of Science for Land Development, Land Development Department, Bangkok, Thailand. Temperaturee is an important and practical parameter indicating the rate and extent of composting and maturity of compost (Tiquia et al., 996) [7], so the composting temperature and ambient temperature were recorded by using thermocouple type T that connected with data logger and installed at the middle of the composting pile to recording the data every 0 minutes until the termination of the composting trial. III. RESULTS AND DISCUSSION OF LABSCALED A. The proportion of sewagee sludge, woodchip, and recycled compost The temperature profiles of each labscaled mixture of SS, WC and RC are shown in Fig. II, Fig. III, Fig. IV and Fig. V. The temperatures of the experiment no.,,, and reached the thermophilic phase within days of composting, and showed rapid initiation of the composting processs (Meunchang et al., 00) [8]. However, the temperature profiles were different for the three experiments. For experiment no., the temperatures reached the peak temperatures of 6. o C, 7. o C, 7. o C and 8.6 o C for the proportion of :0.:0, :0.:0., :0.:0., and :0.: (SS:WC:RC mixtures) on day.6, day.7, day., and day 0.9, respectively. The temperature decreased gradually after the peak. The decreased of the temperature was faster for the mixtures with smaller ratios of RC added. The more ratios of RC added gave the better results in reheat potential of pile turning at day 7 (Fig. II). For the second experiment, a trend of the composting was not much different with the first experiment but in the case of :0.:0. (SS:WC:RC), a temperature decreased faster than other cases. The temperatures reached the peak temperatures of 6.9 o C,.7 o C,.7 o C and 7.9 o C for the :0.:0, :0.:0., :0.:0., and :0.: (SS:WC:RC mixtures) on day.8, day.7, day.9, and day.7, respectively (Fig. III). For the third experiment, the trend of the composting still was not much different with the first two experiments, the temperature decreased slower with a case of more RC added. The temperatures reached the peak temperatures of 60 o C,.8 o C,.9 o C and o C for the ::0, ::0., ::0., and :: (SS:WC:RC mixtures) on day 0.9, day., day.7, and day.7, respectively (Fig. IV). For the forth experiment, the temperature of both cases are almost not passed a thermophilic stage (0 o C ) with the peak temperature of 0. o C and 0. o C for the :0:0, and :0:0. (SS:WC:RC mixtures) on day 9., day. are shown in Fig. V. However, to identify composting performance is quite difficult sometimes, so for the evaluation of reactor simulation performance, we proposed that a quantitative assessment of a temperature time profile may be made by using: (i) the area bounded by the temperature curve and selected baselines, (ii) the time for which baseline temperatures are equaled or exceeded, and (iii) the times taken to reach peak temperatures. Both 0 and C are useful reference temperatures, indicating the extent of thermophilic activity, and exposure of material to recommended disinfection conditions, respectively (Mason and Milke, 00) [9]. For the highest value of A0 was occurred at the case of :0.: SS:WC:RC. The values of A0 of each case are shown in table III. TABLE III. VALUE OF THE A0 Case no SS: WC: RC (v: v: v) :0.:0 :0.: 0. :0.:0. :0.: :0.:0 :0.:0. :0.:0. :0.: ::0 ::0. ::0. :: :0:0. :0:0. A0 (days o C) Figure. Showing the temperature profiles of experiment Figure. Showing the temperature profiles of experiment 77

4 Figure. Showing the temperature profiles of experiment Figure. Showing the temperature profiles of experiment A. The nutrientt determination The nutrientt determination can be represented the quality of the final compost. It can be classified the compost product into fertilizer, soil conditioner, or nothing. In this study the nutrient determination will be compared with Thai fertilizer standard. Nutrient determinations of each case are shown in table IV. TABLE IV. NUTRIENT DETERMINATION Properties Organic matter Moisture conten C?N N P K ph EC (ds/m) Standardd >0 < 0: > > 0. > < Properties Organic Standard > matter Moisture 0.0 content C?N < 0: N >.0 P > 0..7 K > ph EC < (ds/m) From the nutrient determination table, there are only cases have passed all of the fertilize standard which are case no. (:0.:0 SS:WC:RC), case no. 9 (::0 SS:WC:RC), case no. 0 (::0. SS:WC:RC), and case no (::0. SS:WC:RC) so this cases can be classified as a fertilizer and the other cases that didn t pass can be classified as a soil conditioner. Electrical conductivity and ph seem to be a problem with most of the cases that didn t passs the fertilizerr standard but these cases got only a few lower or higher values than standard. For the cases that mixed with RC, it have passed all of the N, P, and K standard which is the main nutrient that plant need for growing but for the cases of no RC added, it haven t passed standard of K for both cases. IV CONCLUSION OF LABSCALED COMPOSTING From the labscaled results, we can conclude that RC can be improved for reheating potential of the pile compost after turning but it not improved much in the earliest stage of the composting. The peak temperature of each experiment occurred in case of no RC was mixing in composting proportion because substrate concentration is the parameter that specific the peak temperature and the heat capacity. From case no and it is obviously shown that WC is one of the most important amendments needed in composting. RC cannot replace the WC for using as a pure amendment (bulking agent). If we considered only A0 not include the nutrient determination, the best two degradation rates would be case no. 8 (:0.:, SS:WC:RC) and case no. 7 (:0.:0.,SS:WC:RC), respectively. if we consider both nutrient determination and A0, the best two degradation rate would be case no. (:0.:0, SS:WC:RC) and case no. 9 (::0, SS:WC:RC) but this two cases were not improved a reheat potential after the pile turning and cannot maintainn the composting temperature as well, so this two proportion is not the suitable proportion for STR technology which has an advantage in pile turning process. Then, the optimal proportions for STR composting by using SS as a substrate are the proportions of case no. 0 (::0., SS:WC:RC), and case no. ( ::0., SS:WC:RC) which passed all of the fertilize standard and also improved a reheat potential after a pile turning as well. 78

5 ACKNOWLEDGMENT Wachcharadej Boonlualohr, Author would like to thanks to Assoc. Prof. Dr. Taweep Chaisomphob as an advisor of this project for his valuable guidance, continuous encouragement and close supervision throughout the study. REFERENCES [] Kanat, G., Demir, A., Ozkaya, B., Bilgili, M.S., Addressing the operational problems in a composting and recycling plant. Waste Management 006;6: 89 [] Banegas, V., Moreno, J.L., Moreno, J.I., Garcia, C., Leon, G., Hernandez, T., Composting anaerobic and aerobic sewage sludges using two proportion of sawdust. Waste Management 007;7: 77 [] Akhtar, M., Malik, A., Role of organicsoils amemdments and soil organisms in the biological control of plantparasitic nematodes: a review. Bioresour. Technol 000;7: 7 [] Golueke, C.G., Diaz, L.F., Historical review: composting and its role in municipal waste management. In: Bertoldi, M., sequi, P., Lemmes, B., Papi, T. (Eds.), th Science of Composting, Part. Blackie, Glasgow 996: pp. [] Bongochgetsakul, A., Chaisomphob, T., Sungsomboon, P., Roongkanaporn, H., Bongochgetsakul, N., and Ishida, T., 006. Novel composting system for organic solid waste treatment at Thammasat University, Lampang. Thammasat International Journal of Science and Technology. [6] Li, X.J., Zhang, R.H., Pang, Y.Z., Characteristics of dairy manure composting with rice straw. Bioresource Technology 008;: [7] Tiquia SM, Tam NFY, Hodgkiss IJ. Effect of bacterial inoculums and moisture adjustment on composting of pigmanure. Environ Pollut 997;96: 67. [8] Meunchang, S., Panichsakpatana, S., Weaver, R.W., Cocomposting of filter cake and bagasse; byproducts from a sugar mill. Bioresource Technology 00.;96: 7. [9] I.G. Mason and M.W. Milke, 00. Physical modeling of the composting environment, Department of Civil Engineering, University of Canterbury, Christchurch, New Zealand 79

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