Characterization and photodegradation pathway of the leachate of Matuail sanitary landfill site, Dhaka South City Corporation, Bangladesh.

Abstract This study was carried out to characterize the biogeochemical and physicochemical properties of landfill leachate from Matuail Sanitary landfill site, Dhaka, Bangladesh. In addition, the study also aimed to identify the photodegradation of landfill leachate under natural sunlight. The leachate pH was slightly alkaline (7.87-8.07) with a minimum level of dissolved oxygen, and low BOD5/COD ratio that are indicators of the matured methanogenic phase. Ca, Fe, Br, Rb, Cu was present in a considerable amount. A trace amount of Sr, Co, As, Pb, Cr was found in the leachate sample. Fourier Transform - infrared (FTIR) spectra of all three samples had five major peak regions notably at 3440-3450 cm−1 (O–H groups of water), 1638 cm−1 ( C==O Amide I, carboxylates C=C, aromatic ring modes, or alkenes), 1385-1390 cm−1 (deformation of the C–H bond in CH2 and CH3, or the asymmetric stretching of COO¯), 1115 cm−1 (stretching of the C–O bond in phenol ethers and phenols) and 605 cm−1 (S–O bends of sulfates). In addition to the appearance of new peak, peak shifting on the 2nd-day and 5th-day phototreatment are in compliance with the 34% TOC reduction. From analyzing three-dimensional excitation/emission (3D-EEM) spectra of the raw sample pyrene-like or humic-like peak A (Ex 255/Em 465), soil fulvic-like peak Mp (Ex 315/Em 450), and humic-like peak C (Ex 370/455) was found indicating more humified characteristics of the mature landfill site. From 1-hour to 6-hours phototreatment, all three substances slightly lost fluorescence intensity. From the 2nd day to the 5th day of photo-treatment, two unknown photo-product was identified within Ex 210.0/ Em 457.0 and Ex 205.0/Em 408.0 at peak A region. Fluorescence intensity lost was 65% for peak A and 44% for peak C. Soil fulvic-like peak Mp was absent on the 5th day of photo-treatment.