Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai

The generation and seasonal variations of secondary pollutants were investigated during three municipal solid waste (MSW) compression and transfer in Shanghai, China. The results showed that the raw wastewater generated from three MSW transfer stations had pH of 4.2-6.0, COD 40,000-70,000 mg/L, BOD5 15,000-25,000 mg/L, ammonia nitrogen (NH3-N) 400-700 mg/L, total nitrogen (TN) 600-1500 mg/L, total phosphorus (TP) 50-200 mg/L and suspended solids (SS) 1000-80,000 mg/L. The pH, COD, BOD5 and NH3-N did not show regular change throughout the year while the concentration of TN, TP and SS were higher in summer and autumn. The animal and vegetable oil content was extremely high. The average produced raw wastewater of three transfer stations ranged from 2.3% to 8.4% of total refuse. The major air pollutants of H2S 0.01-0.17 mg/m3, NH3 0.75-1.8 mg/m3 in transfer stations, however, the regular seasonal change was not discovered. During the transfer process, the generated leachate in container had pH of 5.7-6.4, SS of 9120-32,475 mg/L. The COD and BOD5 were 41,633-89,060 mg/L and 18,116-34,130 mg/L respectively, higher than that in the compress process. The concentration of NH3-N and TP were 587-1422 mg/L and 80-216 mg/L, respectively, and both increased during transfer process. H2S, VOC, CH4 and NH3 were 0.4-4 mg/m3, 7-19 mg/m3, 0-3.4% and 1-4 mg/m3, respectively. The PCA analysis showed that the production of secondary pollutants is closely related to temperature, especially CH4. Therefore, avoiding high temperature is a key means of reducing the production of gaseous pollutants. And above all else, refuse classification in source, deodorization and anti-acid corrosion are the important processes to control the secondary pollutants during compression and transfer of MSW.