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demand for the oxidation of the available organic matter. In addition, at the latest stage of the process, the level of oxygen increased and exceeded the 20% on the 22 nd day indicative of the low rate of organic matter decomposition since the oxygen nearly reached the atmospheric oxygen level. It must also be mentioned that the steep decrease of oxygen content on the 8 th day of the process was due to the suspension of the agitation system operation which was caused by a malfunction to the bioreactor’s motor which was restored immediately as explained below. 5.1.5.5. Reprogramming the plc of the in-vessel bioreactor The agitation system operation was out of order on the 8 th day of the composting process since a malfunction occurred to the bioreactor’s motor and all the operations of the automated control system were suspended. At that time the aeration of the substrate was handled manually from the control panel. After the problem had been restored the operation of the bioreactor was reprogrammed and restarted using the initial settings stated in paragraph 5.1.5.1. 5.1.5.6. Monitoring and maintenance during composting Throughout the duration of the composting process the electromechanical equipment and the rest of the bioreactor’s components and infrastructure were monitored daily in order to maintain their operational status. The regular maintenance of all the electromechanical equipment of the system was performed according to the suggestions of the manufacturer (e.g. lubrication, cleaning the filter of the ventilation system, cleaning the head of the piping system, leachate removal). In addition, daily cleaning of the floor and surface of the bioreactor was performed in order to obtain high hygiene level for the personnel. 5.1.5.7. Disruption and startup of of the bioreactor operation The disruption of the in-vessel bioreactor operation on the 8 th day involved only the operation of the agitation system of the bioreactor and that of the hydration system. The operation of the ventilation system was controlled so that the gases emitted during the process were being removed through the bioreactor’s air suction system 38
which disperses gases through an air-pipe to the bio-filter area 5 in order to prevent undesirable odours within the building where the bioreactor is installed. 5.1.5.8. Restoration of malfunctions and maintenance of the bioreactor During the 8 th day of the composting process a malfunction occurred to the motor of the in-vessel bioreactor. The chain providing motion to the revolving axle was broken. The revolving axle comprises of stirring elements responsible for the agitation of the substrate. The malfunction was restored and the bioreactor started to operate again on the 9 th day of the composting process. 5.1.6. Sampling and analysis of the substrate Substrate samples were taken every 6 to 8 days of the composting process and the examined parameters included the pH, total carbon, total nitrogen, nitrates (NO - 3 - N) and ammonium (NH + 4 - N). 5.1.6.1. pH The acidity or alkalinity of the material, referred to as pH, is also an important parameter of composting. The pH determines the species of microrganisms that will be developed for the biodegradation of the organic fractions. The effects of pH on the composting process are directly related to the effect of pH on microbial activity and more specifically on microbial enzymes. However composting process is relatively insensitive to pH within the range commonly found in mixtures of organic materials. Although composting process can work over a wide spectrum of pH values, a range between 6.0 and 8.5 is preferred [2, 3]. Figure 5 presents the pH evolution during the 1 st composting trial. 5 the bio-filter bed was filled with the end product resulted from the 1 st composting trial 39
Page 1 and 2: U C D UNIVERSITE CHOUAIB DOUKKALI N
Page 3 and 4: 5.1.4. Feeding the in-vessel biorea
Page 5 and 6: 5.4.5.4. Measuring the oxygen conte
Page 7 and 8: Table 9: Typical nutrient compositi
Page 9 and 10: The temperature profiles of the com
Page 11 and 12: 1. Introduction to composting proce
Page 13 and 14: 2.2. Particle size, porosity, struc
Page 15 and 16: This will limit the movement of air
Page 17 and 18: sludge treatment is an immense prob
Page 19 and 20: Due to the unavailability of the UW
Page 21 and 22: Table 1: Parameters evaluated the s
Page 23 and 24: 4.2. Composting mixtures The chemic
Page 25 and 26: The ventilator system can operate X
Page 27 and 28: 4.4. Sampling and analysis of the s
Page 29 and 30: 5. Results and discussion The compo
Page 31 and 32: fertilisers. According to Table 2 t
Page 35 and 36: eplaced by others that are thermoph
Page 37: ventilation of the substrate is a v
Page 41 and 42: [ % ] 45 40 35 30 25 1 3 5 7 9 11 1
Page 43 and 44: acquired due to processes of non-sy
Page 45 and 46: [mg/kg] 1400 1200 1000 800 600 400
Page 47 and 48: which occurs through the bio-oxidat
Page 49 and 50: Table 7: Suggested limit values for
Page 51 and 52: Cd (mg/Kg d.s) 0.4739 Cr (mg/Kg d.s
Page 53 and 54: decomposition can pose an indirect
Page 55 and 56: produced from the 1 st trial is cla
Page 57 and 58: Biological assays To estimate the r
Page 59 and 60: 5.1.10. Preparing the system for th
Page 61 and 62: K, as K 2 O (% d.s) 0.9670 4.2683 3
Page 65 and 66: 5.2.5.3. Measuring the moisture of
Page 67 and 68: 5.2.5.6. Monitoring and maintenance
Page 69 and 70: [ % ] 50 45 40 35 30 1 3 5 7 9 11 1
Page 71 and 72: 5.2.6.4. Ammonium Nitrogen (NH + 4
Page 73 and 74: parts carbon for each part of nitro
Page 75 and 76: educed and on the 18 th day ammoniu
Page 77 and 78: With respect to the ammonium and ni
Page 79 and 80: % d.s. Dissolved in H2O Dissolved i
Page 81 and 82: 5.3. Composting using primary sludg
Page 83 and 84: is used for agricultural purposes w
Page 87 and 88: material. Only after all substrate,
Page 89 and 90:
conditions in the bioreactor. At th
Page 91 and 92:
[ % ] 40 35 30 25 20 1 3 5 7 9 11 1
Page 93 and 94:
[ mg/Kg ] 800 700 600 500 400 300 2
Page 95 and 96:
C:N ratios as has been shown in Tab
Page 97 and 98:
leachates through the ion exchange
Page 99 and 100:
[2, 3, 4, 5, 6] for the development
Page 101 and 102:
[% d.s.] Dissolved in H2O Dissolved
Page 103 and 104:
5.4. Composting using secondary slu
Page 105 and 106:
5.4.2. Composition of the compostin
Page 107 and 108:
operation as well as the water flow
Page 109 and 110:
can become anaerobic. As has been m
Page 111 and 112:
pH 10 9 8 7 6 5 1 2 3 4 5 6 7 8 9 1
Page 113 and 114:
[ % ] 6 5,5 5 4,5 4 1 2 3 4 5 6 7 8
Page 115 and 116:
5.4.6.5. Nitrates (NO - 3 - N) Besi
Page 117 and 118:
Table 36: Characteristics of leacha
Page 119 and 120:
NH 4+ - N (mg/Kg.d.s) 304.10 Total
Page 121 and 122:
Heavy metals speciation Furthermore
Page 123 and 124:
Faecal coliforms Log10 MPN/10g DS 0
Page 125 and 126:
the degradation and stabilization o
Page 127 and 128:
Table 40: The physicochemical chara
Page 129 and 130:
7. References [1] Malamis, S. (2000
Page 131 and 132:
[29] Pagans, E., Barrena, R., Font,
Page 133 and 134:
[56] Zorpas, A.A., Arapoglou, D., P
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