Treatment options for effluents from a solid waste transport station

In this study the wastewaters originating from solid waste transport stations that are established to compress the collected solid wastes from households in order to ease further transportation to final disposal sites (e.g. sanitary landfills) were investigated in terms of characterization and treatability. The results of conventional characterization showed that although the strength of wastewater may be subject to changes depending on the amount of water used for site cleaning, the effluents can be classified as strong wastewaters. Unlike the landfill leachates the mentioned wastewaters did not contain excessive amounts of nitrogen. The soluble COD of the wastewaters accounted for approximately 80% of the total COD, emphasizing the predominance of soluble organic pollutants. To remove soluble organics on the other hand, although both chemical oxidation processes and biological treatment such as aerobic systems; anaerobic technologies or a combination of both anaerobic and aerobic processes can be applied, biotreatment overcomes chemical oxidation due to economic concerns. Assessment of inert COD fractions under aerobic and anaerobic conditions indicated that an anaerobic process must be applied as the first unit of the treatment scheme. However since it was not possible to comply the discharge limitations of 160 mg l–1 COD by solely using an anaerobic biological treatment, an additional treatment unit i.e. aerobic biological treatment or chemical oxidation etc. following the anaerobic one must be used. It was recommended to run additional experimental research to find out more about both the proper type and the optimal operating conditions of the mentioned second treatment unit.

The results of conventional characterization indicate that the effluents originated from a solid waste transport station can be classified as a wastewater having a strong nature. Due to the variable amount of water used for site cleaning the strength of the effluents may subject to changes. The Table 2 Results of the inert COD experiment under aerobic and anaerobic conditions Inert COD test Reactor I fed with wastewater (COD, mg l–1) Reactor II fed with filtered wastewater (COD, mg l–1) CT ST CT ST Aerobic Sample content Start of the experiment End of the experiment Duration, h — — Anaerobic Sample content Start of the experiment End of the experiment Duration, h — — Table 3 Evaluation of the inert COD experiment (COD, mg l–1) Parameters Under aerobic conditions Under anaerobic conditions Initial COD of the sample, CT0 Soluble inert COD of the sample, SI0 Soluble microbial products, SP Particulate inert COD of the sample, XI0 Particulate microbial products, XP soluble COD of the wastewaters accounts for approximately 80% of the total COD. It should be emphasized that unlike landfill leachates, these effluents do not contain high amounts of nitrogen. The outcomes obtained from the inert COD studies show that aerobic and anaerobic treatment is likely to generate similar soluble residual COD fractions although a slightly better result is obtained with anaerobic treatment. This fact together with the strong nature of the effluent favors anaerobic treatment over aerobic one as the first stage of treatment. However the application of only anaerobic treatment is not adequate to meet the effluent limitations of 160 mg l–1 COD as initially refractory soluble COD and metabolic inert COD produced throughout the course of anaerobic biotreatment totally accounts for a soluble COD of 1366 mg l–1. Therefore the anaerobic first unit must be supported by applying a subsequent treatment process such as aerobic biological treatment or chemical oxidation. It is recommended to extent the current research by generating additional experimental data both on the type and optimum operating conditions of this second treatment unit.