Bioreactor Leachate

Subsequently, biological/physical treatment of leachate with an activated carbon-enhanced sequencing batch bioreactor (PAC-SBR) was analyzed to determine whether the improved treatment by simultaneous adsorption and biodegradation in the SBR would produce an acceptable effluent without post-treatment in the existing granular activated carbon adsorber (Ying et al., 1986). 

Ying, W.C., R.R. Bonk and S.A. Sojka. Treatment of Landfill Leachate in Powered Activated Carbon Enhanced Sequencing Batch Bioreactors. In Proc. of the 18th Mid-Atlantic Ind. Waste Conference, Technomic Publishing Company, Inc., Lancaster, Pennsylvania, 1986. 

In engineering terms, a sanitary landfill is also sometimes identified as a bioreactor due to the presence of anaerobic activities in the wastes. As such, landfilling sites need the incoming waste stream top be monitored, as well as placement and compaction of the waste, and installation of landfill environmental monitoring and control facilities. Gas vent and leachate collection pipes are important features of a modem landfill. 

The aerobic biofilter used in the study had a capacity of 10 L. The reactor was packed to 60% of the empty bed volume with Cosmo ball media. The biofilter was seeded with active innoculum taken from an active aerated lagoon of a nearby landfill leachate treatment. Fresh raw leachate was used as feed to the reactor at a rate of 5 L/d over 24h. The loading rates applied to the bioreactor were between 1.6 and 22.2 kg COD/m3d. Initial studies were conducted as a batch process lasting for a period of 24 d. Thereafter, the biofilter was fed continuously for a total period of 240 d. 

When aquifers were amended with nitrate in order to stimulate biodegradation, the results were generally consistent with those obtained in laboratory investigations. In a field injection experiment at Seal Beach, California, Ball et al. (1994) demonstrated complete removal of w-xylene and the m-,/-xylene fraction decreased significantly in parallel bioreactor experiments. A Canadian study showed a decrease in m- and /-xylene of 14% and 15%, respectively, over aim flowpath in the Borden aquifer (Barbara et al., 1992). Very little degradation was observed beyond that point, presumably due to the availability of preferred electron donors in the landfill leachate impacted aquifer. 

The SLillide produced from sulfate reduction plays a major role in metal sul-lide immobilization in sediments but has also been applied to bioremediation of metals in waters and soil leachates. One process used sulfur- and iron-oxidizing bacteria to liberate metals from soils in the form of an acidic sulfate solution that enabled almost all the metals to be removed by bacterial sulfate reduction (White et al., 1998). Large-scale bioreactors have in fact been developed using bacterial sulfate reduction for treating metal-contaminated waters (Barnes et al., 1992 Gadd, 1992b). 

White, C., and Gadd, G. M. (1997). An internal sedimentation bioreactor for laboratory-scale removal of toxic metals from soil leachates using biogenic sulphide precipitation. J. Ind. Microbiol. Biotechnol. 18, 414-421. 

K. Tamacki, S. Lyko, T. Wintgens, T. Melin, F. Natan, Impact of extra-cellular polymeric substances on the filterabUity of activated sludge in membrane bioreactors for landfill leachate treatment. Desalination 2005,179,181-190. 

It is evident therefore, that landfill gas production may be increased significantly by the addition of water, but that the volume of leachate will necessarily increase. The addition of water is a key requirement of the bioreactor landfill, and arguments relating to the advisability and technology of this landfill principle are discussed in Chapter 7. If the rates of waste degradation within landfill are to be increased, then optimisation of moisture content and flow is essential. For this to be achieved, effective control and treatment of leadiate will be necessary. However, the addition of excess moisture may not be necessary The moisture content of municipal solid waste is typically 20-30% in develop ... 

For effective co-disposal, the draft document for consultation (DoE, 1994a) states that "flushing bioreactor conditions are needed. This leads to a separate requirement for containment and possibly recirculation" (see Chapter 7). Under enlumced conditions of gas generation (and hence microbial activity) the potential for effective co-disposal will be enhanced accordingly. Although at the moment very few landfill sites undertake leachate recirculation, it is a concept that is receiving a great deal of attention and one that appears to facilitate both codisposal practice and more sustainable landfill development. 

An alternative bioreactor concept - the fermentationAeaching wet cell (F/L wet-cell) has been developed by Lee and Jones-Lee (1993). This concept also aims to effectively stabilise the waste and leach the soluble potentially polluting components. The design requires that the waste is shredded prior to emplacement to try to ensure contact of the liquid with all waste components. According to Lee and Jones-Lee (1993) who cite Ham (1975), this will also eliminate the need for daily cover, and has the potential to increase the capacity of landfill by about 20%. The other key feature of F/L wet-cell is the use of a clean water system beneath the clay of the composite liner to maintain movement of water up through the clay, thus preventing any leachate leakages to escape from the containment system. 

Figure 3.8 (a) A membrane bioreactor-based system for treating landfill leachates, (b) A multi-staged RO and reject RO integrated membrane system for treating landfill leachates. Source [17]. 

The application of FO in recent years has expanded, not only in terms of installed capacity but also in the diversity of industries where the technology has been installed. Applications such as power generation, desalination, wastewater treatment (osmotic membrane bioreactor) and liquid food concentration are reported in the literature [4]. Commercial FO products are available for a variety of applications including personal water filtration and desalination, oil gas drilling water reclamation and landfill leachate treatment. 

Treatment of contaminated liquids such as water, leachate, filtrate, groimdwater, storm water, surface water and industrial process waste water can be accomplished by several of SBP s technologies. Certain waste streams can be concentrated by the hyperfiltration units the permeate is clean water and the "ctMicentrate" contains the reduced volume of the pollutants. These concentrated contaminants can often be bioremediated, thus minimizing the waste stream. Other liquids may be treated directly, either by biological processes, or in the case of volatiles, air stripping with biotreatment of the pollutants in a gas phase bioreactor, or "biofilter". 

Zayen, A., Mnif, S., Aloui, F., Fki, F., Loukil, S., Bouaziz, M., et al. (2010). Anaerobic membrane bioreactor for the treatment of leachates from Jebel Chakir discharge in Tunisia. Journal of Hazardous Materials, 177, 918—923. 

Shao L et al (2006) Electrolytic degradation of biorefractory organics and ammonia in leachate from bioreactor landfill. Water Sci Technol... 

Designing a system for leachate recirculation and distribution of liquids inside the bioreactor landfill. 

More detailed control and monitoring of waste settlement, landfill gas, and leachate production and composition during the bioreactor s operational phase is necessary. 

Decrease of pollutant concentrations in the leachate. Positive effects in the reduction of leachate strength in a full-scale bioreactor landfill were observed at Sea Carr Landfill. The COD in the leachate from the area with recirculation was always lower than in the control area (without recirculation). The differences became more apparent with time. After three years of observation the COD values in the recirculated leachate were approximately 15 g dm while in the control they exceeded 50 g dm . A similar trend was observed in the case of chlorine, and ammoniacal-N. During three years of observations concentrations of these substances decreased in both cells, but the lower values and a more pronounced drop were noticed in the cell where leachate recirculation was applied. After three years, the chlorine and ammoniacal-N concentrations in the recirculated leachate was about 1,600 and 500 mg dm" respectively, while in the leachate from the control cell they were about 2,100 and 800 mg dm, respectively (Bioreactor Landfill for Sustainable..., 2004). Recirculation of leachate from an active or closed landfill cell can be considered as an in situ leachate treatment method. It minimizes the hazard to the environment and reduces the leachate treatment costs (Reinhart et al. 2002). Due to the continuous recirculation of leachate the operator does not bear the costs associated with its pre-treatment and transport to the treatment plant. 

In addition to accelerated waste decomposition, the other important advantage of hybrid bioreactor landfill technology is the high efficiency of nitrogen removal from the leachate. Oxy-... 

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