Introduction

Bioreactor Landfill

General Types of Bioreactor Landfill

Advantages

Definition of terms

Definition of terms

• archaea– The Archaea constitute a domain or kingdom of

single-celled microorganisms. These microbes are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells. (Wikipedia)

• Methane Gas– Together with Co2, over 90% produced from the

decomposition of solid wastes. With Proper venting at the landfill source, methane should not pose a problem.

• Volatile Organic Compounds (VOCs)– Cause air quality issues such as smog and

ozone formation. VOCS comprise about 39% of NMOC (nonmethane organic compounds).

• Leachate– Leachate may be defined as liquid that has

percolated (penetrated) through solid waste and has extracted dissolved or suspended materials from it. Under normal conditions, leachate is found in the bottom of landfills.

• SOLid waste stabilization– stabilization is one of the cleanup methods that

prevent or slow the release of harmful chemicals from wastes, such as contaminated soil, sediment, and sludge. This method usually do not destroy the contaminants. Instead, they keep them from “leaching” above safe levels into the surrounding environment. Leaching occurs when water from rain or other sources dissolves contaminants and carries them downward into groundwater or over land into lakes and streams.

– Stabilization causes a chemical reaction that makes contaminants less likely to be leached into the environment. it is often used together with solidification to prevent people and wildlife from being exposed to contaminants, particularly metals and radioactive contaminants.

Introduction

Landfills are the oldest known method of waste disposal.

Waste is buried in large dug out pits and covered. Bacteria and archaea decompose the waste over

several decades producing several by-products of importance, including methane gas (natural gas), leachate fluid and volatile organic compounds (such as hydrogen sulfide (H2S), N2O2, etc.).

****With the increasing amount of waste produced, appropriate places to safely store it have become difficult to find.

Bioreactor Landfill

A bioreactor landfill operates to rapidly transform and degrade organic waste. The increase in waste degradation and stabilization is accomplished through the addition of liquid and air to enhance microbial processes.

Bioreactor Landfill

Three general types of bioreactor landfill:1. Aerobic2. Anaerobic3. Hybrid (Aerobic-Anaerobic)

Bioreactor Landfill

Aerobic Leachate is removed from the bottom layer, piped to liquids storage tanks, and re-circulated into the landfill in a controlled manner. Air is injected into the waste mass, using vertical or horizontal wells, to promote aerobic activity and accelerate waste stabilization and amount of VOCs, toxicity of leachate and methane are minimised.

leachate monitoring parameters

The leachate parameters that are generally-accepted as the most useful for evaluating waste stabilization and leachate recirculation operational efficiency include:

The parameters to be monitored quarterly constitue the primary leachate recirculation parameters used for both operational control and long term performance monitoring. The key parameters to assess stabilization progress include ph, COD, BOD, and nitrogen forms.

Bioreactor LandfillAnaerobic

Moisture is added to the waste mass in the form of re-circulated leachate and other sources to obtain optimal moisture levels. Biodegradation occurs in the absence of oxygen (anaerobically) and produces landfill gas. Landfill gas, primarily methane, can be captured to minimize greenhouse gas emissions and for energy projects. The high concentration and quantity of methane allows it to be used more efficiently for commercial purposes while reducing the time that the landfill needs to be monitored for methane production.

why moisture is added?

Landfill degradation of MSW frequently is rate-limited by insufficient moisture. The average landfilled MSW has a moisture content of only 25% wet weight. However, it was found that the maximum methane production in landfills occurred at moisture content of 60-80% wet weight. This suggests that most landfills are well below the optimum moisture content for methane production.

Liquid can be injected into the waste via horizontal trenches, vertical wells, surface infiltration ponds, spraying, and prewetting of waste.

If the waste is wetted too rapidly, a buildup of volatile organic acids might lower the leachate pH, inhibiting the methane-producing bacteria population and reducing the rate of biodegradation.

The gas content of anaerobic bioreactors is similar to that of conventional landfills, with methane and carbon dioxide each making up approximately 50% of the total LFG volume. When the methane content of the LFG exceeds approximately 40%, the methane-producing bacteria population can be considered established. A decrease in the methane gas content below 40% is a possible indication that the waste is becoming too wet or dry. Once the methane-producing bacteria population has become established, the rate of leachate recirculation may be increased.

Bioreactor Landfill

Hybrid (Aerobic-Anaerobic)The hybrid bioreactor landfill accelerates waste degradation by employing a sequential aerobic-anaerobic treatment to rapidly degrade organics in the upper sections of the landfill and collect gas from lower sections.

Advantages

Decomposition and biological stabilization of the waste in a bioreactor landfill can occur in a much shorter time frame than occurs in a traditional “dry tomb” landfill providing a potential decrease in long-term environmental risks and landfill operating and post-closure costs. Potential advantages of bioreactors include:

Decomposition and biological stabilization in years vs. decades in “dry tombs”.

Lower waste toxicity and mobility due to both aerobic and anaerobic conditions.

Reduced leachate disposal costs.A 15 to 30 percent gain in landfill space due to a decreas

e in landfill mass.Significant increased LFG generation that, when capture

d, can be used for energy use onsite or sold.Reduced post-closure care