Abdul Jalil*
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Samiul Basar
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Santosh Karmaker
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Ashraf Ali
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Mahbuboor Rahman Choudhury
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Shamsul Hoque
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Bangladesh
Anaerobic digestion; Biodegradable waste; Biogas; Hydraulic retention time; Single chamber reactor; Double chamber reactor
Madbarer Char bazaar (a large size market) of Shibchar Upazila of Madaripur district of Bangladesh
Resource Development and Management
Bio-gas, Vegetables, Cattle
Selected market and composition of waste Madbarer Char bazaar (a large size market) of Shibchar Upazila of Madaripur district of Bangladesh was selected for the study. It consists of both permanent and temporary shops (about 1500 nos.) including open spaces for cattle and goat market. This market is usually functional twice a week – on haat days (Sunday and Thursday). On Thursday, the haat is usually the largest. Cows and goats are sold only on that day. Large amount of vegetables are sold on both Sunday and Thursday. Twenty restaurants are operated only on the haat days and 7-8 tea stalls serve on other days of the week. On non-haat days, milk, fishes and very limited amount of vegetables are sold. Not much commodities are sold on other five days of the week. Two labors were appointed to collect, separate, store and measure the wastes on two consecutive haat days. They collected all the wastes produced in a whole day and separated each item and kept them in different sacks. Figure 2 shows collection of wastes by two labors in a plastic bucket. The amount of individual item was measured using an electronic weighing scale after the hat was over. It is found that the amount of wastes generated on Thursday was about 25% greater than those on Sunday. On the haat day, the average amount of easily biodegradable waste was found to be 644 kg out of the total waste of 1054 kg. About 61% of the waste generated was biodegradable. Cow dung, fish waste, ginger, cursed lobe, guava, and banana leaf were the major biodegradable wastes. Goat droppings, bitter melon, brinjal, dhundul, and pointed gourd were the minor biodegradable wastes.
Experimental setup In order to generate basic data on biogas generation, experiments were run in two phases. In the first phase, batch reactors were operated and in the second phase, daily feed reactors were operated. The same composition of the easily biodegradable portion of the market waste was used in both the phases. Daily average composition of the biodegradable wastes was determined on the basis of the average waste generation on the haat days per week. Experiments were conducted using this daily average composition. At the onset of the experiments, the TS (Total solids) and VS (Volatile Solids) of the biodegradable wastes were determined. The biodegradable wastes were cut into small pieces (maximum dimension of 4 mm) before feeding a reactor (anaerobic digester). A glass bottle of 2.5 liter capacity was used as batch reactor for biogas generation. Two batch reactors were set up in the Environmental Engineering Laboratory of BUET in the first phase of the experiments. The effluent of the biogas plant of Jahangirnagar University was used as the liquid of the digester to ensure the abundance of active microbes for biogas generation. The digester was placed in a closed chamber made of Thai Aluminium and two electrical room heaters were placed inside the chamber to maintain a constant temperature. The heaters were operated alternatively. Biogas was collected in a gas holder using water displacement method. In the second phase of the experiments, two daily feed reactors - one single chamber reactor and one double chamber reactor (two reactors connected in series) were set up in the Environmental Engineering Laboratory of BUET. A plastic container fitted with an inlet tube at the mid height and an outlet tube near bottom on the opposite side of the container was used as the single chamber reactor. Two plastic containers were connected with a tube near the bottom and an inlet tube was fitted to the first container at the middle while an outlet tube was attached near the bottom of the second container to make the double chamber reactor. Other arrangements were the same as those in the first phase of the experiments.
Operation of anaerobic digesters In the first phase, the experiments were started on the 18th August, 2016 and ended on the 2nd October, 2016 (total 45 days of operation). In this phase, 500 g and 750 g of the waste were added in two 2.5 L digesters separately and the amount of liquid added was 1500 mL for 500 g waste and 1400 mL for 750 g waste to make the effective volume of 2.1 L. The temperature of the chamber and the volume of gas generation were recorded daily during the experiments. The pH of the contents of the digesters was sometimes measured. Gas leakage from the digester was sometimes not realized, and when this problem was understood/ encountered, remedial measures were taken immediately. The experiments of the second phase were started on the 25th October, 2016 and ended on the 18th December, 2016 (total 53 days of operation). In the single chamber reactor, 750 g waste and 1500 mL inoculum were added at the start of the experiment. Each container of the double chamber reactor was loaded with 375 g waste and 1000 mL inoculum at the beginning of the experiment. The data of the 1st phase experiments revealed that the optimum retention time was 40 days. Hence, 18.75 g of waste was mixed with 37.5 mL of water to prepare the daily feed for the single chamber reactor. From the 2nd day of the operation, this mixture was fed at a time every day through the inlet of the reactor after taking out 55 mL slurry from the reactor through the outlet. For the double chamber reactor, the daily feed consisted of a mixture of 18.75g waste and 50 mL water. The first chamber of the reactor was fed daily with this mixture once after taking out 67.5 mL slurry from the second chamber. The temperature within the Thai Aluminum chamber and the volume of gas generation of each reactor were recorded daily during the experiments. On the 3rd December, 2016, the heater was out of order and the experiments were continued at the ambient temperature up to the end.
Jalil et al., Int J Waste Resour 2017, 7:2
Journal