Session- Composting Applications - Landfills & Bioremediation
Design and Evaluation of Bench-Scale Compost Treatment System for Hazardous Waste
Glaser, John (1), Potter, Carl(1) , Dosani, Majid (2)
(1) U.S. Environmental Protection Agency, National Risk Management Research Laboratory, 26 W. King Dr., Cincinnati, OH 45268, (2) IT Corporation, 11499 Chester Road, Cincinnati, Ohio 45246, USA
Soil-bound contamination presents a significant set of problems to those attempting to remediate the soil. Bioremediation has received considerable attention as a potential answer to the obvious remediation needs. Composting technology represents a promising means to use indigenous microbial activity to degrade contaminants in soil. We have designed a computer controlled compost system that permits the establishment of proper conditions in a compost-contaminated soil mixture. Results derived from this experimentation are expected to give a closer estimate of field-treatment conditions thereby assisting scale-up opportunities. A series of studies on different soils and sediments will be discussed to demonstrate the versatility and ease of operation of this new bench-scale system.
Effect of Lime and Composts On Soil Microbial Populations, Bioremediation of Copper and Yield of Lucerne (Medicago Sativa) of Cu Contaminated Vineyard Soil
KOSTOV, OGNIAN STOIANOV (1), Ngan, T. Y., (2);
(1) Soil Science Institute, 7 Shosse Bankya, 1080 Sofia, Bulgaria; (2), Ngan & Ngan Holdings Sdn Bhd 10th Floor, Wisma Central, Jalan Ampang, 50450 Kuala Lumpur, Malaysia, Bulgaria
Eutric Fluvisol with different history (10, 20 and 30 years old vine) was studied. According to Bulgarian standards the soil was contaminated with Cu from 1.8 to 2.8 degree depending on the pH values. Vineyard soil was additionally treated with CuSO4 in combination with the two composts, which were produced aerobically from vine branches and grape pruning, husks and seeds respectively. Laboratories and pots experiments were then carried out. It was found that bacterial and streptomycetal populations were less tolerant to Cu toxicity than fungal populations. Application of composts had positive effect on normal to Cu-tolerant bacteria ratio. Both composts bioremediated significant amount of toxic copper. No growth of lucerne was established at soil variants, which were not treated with composts. Copper taken up from soil in the top mass was high in all treatments. Combine application of lime, composts and inoculation of lucerne seeds with active Rhizobium meliloti strain drastically increase the top mass of lucerne. The increase was from 37 to 137% with the 10 years old vineyard soil and from 1000 to 1495% with the 20 years old vineyard soil. It appears that the composts used were able to increase soil fertility significantly.
How composting can optimize landfilling
Peter LECHNER (1), Carolin Heiss-Ziegler (1), Marion Humer (1)
(1) BOKU-University of Vienna / Department of Waste Management, Austria
Engineering measures regarding landfilling such as a bottom liner or an impervious final cover, have a service life of only a few decades. Therefore, the occurrence of both landfill gas and long-term leachate emissions cannot be avoided. Our current landfilling practices need to be reviewed. Decomposition processes in landfills usually take place under anaerobic conditions and are therefore fairly time-consuming (up to several decades). By way of a biological pretreatment, however, decomposition is accelerated and takes place within a few months under aerobic and controlled conditions. Thus, the landfilled waste no longer goes through acid fermentation. Depending on duration and quality of the pretreatment, methane formation is largely prevented. A remarkable part of nitrogen is fixed in humic substances. Uncontrolled escape of landfill gas contributes to the greenhouse effect, mainly due to CH4, which is 21 times more effective than CO2. State of the art of landfill gas collection is an active gas recovery and utilization of the calorific value of methane. Biological methane oxidation is an innovative technology for use in landfills with low gas production or in addition to an active gas collection. The methane oxidation technique requires a suitable substrate and design of the cover layer. Compost used in a proper cover design and in combination with a vegetation with high evapotranspiration capacity (C4-plant Miscanthus) can considerably reduce leachate. There is no negative interaction between plant roots and methane oxidizing bacteria. This fact was confirmed by lysimeter-tests continuously charged with landfill gas. Results from laboratory tests and from investigation in the field will be presented.
Biological Stabilisation of Old Landfills Using In-Situ Aeration: Lab Scale Investigations and Full Scale Application
R. STEGMANN*, M. RITZKOWSKI* and K.-U. HEYER**
& Department of Waste Management, TU Hamburg-Harburg, Harburger Schlo str. 36, D - 21079 Hamburg, ** Consultants for Waste Management, Prof. R. Stegmann and Partner; Nartenstr. 4a, D - 21079 Hamburg, Germany
The results of investigations from many old landfills in Germany show that significant emissions occur under anaerobic conditions as they normally appear in the landfill bodies. The significant emissions via the gas phase will last at least 3 decades after the closure of the landfill while significant leachate emissions are predicted for many decades or even centuries. The aim of the aerobic in situ stabilisation of old landfills is to reduce the inventory of organic matter and nitrogen inside the landfill body in order to reduce the emission potential significantly. This aim can be achieved by means of the aerobic degradation processes which are much faster and in many cases more extensive than the anaerobic degradation. This results in a reduction f.e. in hydrocarbons as well as nitrogen in the leachate phase. In principle the same processes are practised in-situ in the old landfills that are used for the biological ex-situ pre-treatment of residual waste before landfilling. This process is used in Germany and many other European countries with increasing tendency. Further more the accelerated aerobic in situ stabilisation has a significant cost saving potential due to a reduction of the aftercare period. In addition there is the possibility in the modification of the cost intensive surface liner system as it is prescribed by the German Technical Guidance Municipal Solid Waste to an alternative surface cover system after the aeration measures have been terminated. Preliminary investigations in 1998 into the aerobic in situ stabilisation of the old landfill Kuhstedt in Lower Saxony, situated about 90 km in the south-west of Hamburg, northern Germany, confirmed the positive effects on the emission reduction by injecting air with a low pressure head into the landfill body. Moreover, the tests proved that an in situ stabilisation can be carried out by means of ordinary technical equipment and with a low energy demand. In order to demonstrate the effects of the aeration on the emission behaviour of the landfilled waste and more over to reach important indications for a successful operation of the installed aeration equipment extensive laboratory investigations have been carried out and in addition are still going on. Therefore waste samples have been taken out of the landfill body while drilling the holes for the installation of the gas wells and investigated in landfill simulation reactors (LSR). The results of these long term investigations, which allow on the one hand the estimation of the long term emission behaviour of the landfilled waste and on the other hand bring important results regarding the emission behaviour during changing the milieu conditions from anaerobic to aerobic conditions, will be presented. In general the tests show that due to the aeration biodegradable organic components (measured as BOD5, COD / TOC) are converted faster and that especially nitrogen concentrations in the leachate can be reduced significantly. Apart from the positive effects on the leachate quality the carbon conversion during the aeration is increased in a considerable way. The full scale realisation of the aeration measures at the old landfill “Kuhstedt” consist of a system of 25 gas wells. The operation and the control of the system ensures via the active aeration of the landfill body and the online analysis of the exhaust gas that only the amount of air is supplied by low pressure into the waste that it is needed for aerobic degradation processes. Each well can either be used for the aeration or for the extraction of the exhaust air which is treated afterwards in biofilters or by non-catalytic oxidation measures. Results of the ongoing aeration measure as well as details respecting the technical implementation of the in situ aeration will be presented.