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Slurry is a dark liquid generated by the decomposition of organic matter and which can cause environmental pollution

Image: Del Barrett in Unsplash

Leachate, also known as leachate or percolated liquid, is a dark liquid generated by the decomposition of organic matter in landfills and dumps or in composting. In addition to having a strong and unpleasant smell, leachate from landfills and dumps can pollute the soil, groundwater and rivers. Compost slurry, in turn, is non-toxic and can be used as a soil fertilizer and natural pesticide.

In composting, the slurry results from the decomposition of pure organic matter, while in landfills and dumps, the various types of disposal are decomposed together and release a contaminated slurry whose disposal requires attention. To avoid impacts on health and the environment, slurry can be treated in four different ways.

Slurry from landfills and dumps

The physicochemical composition of the slurry varies according to factors ranging from environmental conditions and the way in which the waste is discarded to the characteristics of the disposal itself. As they do not offer any type of treatment to the waste deposited, dumps are the places most contaminated by leachate.

In addition to organic compounds, slurry contains substances that are not biodegradable and that do not serve as substrates for microorganisms, such as suspended solids and heavy metals. Therefore, they end up accumulating in the soil, water, plants and animals, potentially causing damage to health and the environment.

The design of a sanitary landfill must provide for the installation of elements for the capture, storage and treatment of leachate and biogas, as well as upper and lower waterproofing systems. These components are essential for the work to be considered safe and environmentally correct. However, there are many deregulated landfills that do not treat the leachate properly, contributing to the aforementioned impacts.

According to the Brazilian geologist and anthropologist Maurício Waldman, this type of slurry is considered one of the most harmful substances known. Along with plutonium and dioxin, slurry is one of the three most dangerous substances in the modern world. Among the heavy and toxic metals that make it up are cadmium, arsenic, copper, mercury, cobalt and lead. The accumulation of these metals in the body can generate numerous problems in the respiratory, cardiovascular and nervous systems.

Impacts caused by slurry from landfills and dumps

Because it has toxic substances in its composition, the leachate can contaminate the groundwater in the vicinity of the landfill. The presence of slurry in groundwater causes extremely serious consequences for the environment and public health. Due to the movement of the sheets, the slurry can disperse and reach artesian wells. Combined with the action of rain, it can be transported on the surface, contaminating the soil and surface water.

compost slurry

In compost, the slurry results from the decomposition of pure organic matter. Therefore, it is non-toxic and can be used as a soil fertilizer and natural pesticide. The transformation of the residue into humus, or organic fertilizer, is carried out by detritivores and decomposers, such as earthworms.

According to data from the Institute for Applied Economic Research (Ipea), more than half of all the garbage we produce at home is organic. All this residue, when discarded in landfills and dumps, together with toxic materials such as batteries, end up producing leachate and other effluents that cause impacts to health and the environment. In addition, untreated waste ends up producing methane gas, which is about 25 times more harmful to the greenhouse effect than carbon dioxide.

It is noteworthy that the cells and batteries must be packed in resistant plastic and disposed of in specific places. See which collection points are closest to your home or place of work on the portal eCycle.

If all organic waste produced in Brazil were treated with compost it would be possible to avoid methane gas emissions, produce about 37.5 tons of humus per year, reduce the spaces occupied in landfills and dumps and also the pollution of soils, sheets water tables and the atmosphere.

The transformation of the residue into humus, or organic fertilizer, is done by detritivores and decomposers, in the case of worms, a group in which California earthworms stand out, as they have greater capacity to adapt to captive conditions and high fertilizer production. organic.

Unlike the slurry produced in landfills and dumps, the slurry from the composter is non-toxic and can be used as a soil fertilizer and natural pesticide. To use it as a soil fertilizer, you need to dissolve each part of slurry in ten parts of water. To use it as a natural pesticide, dissolve the slurry in water in a proportion of half and half and spray it on the leaves of the vegetables in the late afternoon, so that there is no sunburn on the plants.

Manure treatment

Slurry that is harmful to health and the environment can be treated in four different ways.

recirculation

Recirculation consists of draining and capturing the slurry in an accumulation well, and returning it to the interior of the landfill. This recirculation is done by introducing the slurry through the gas drains, or through a network of perforated tubes that distribute this liquid in channels excavated in the landfill surface. Through the biological action of the microorganisms present in the garbage, the toxic effect of the leachate is attenuated. In addition, part of the recirculated slurry also evaporates.

biological treatment

The biological treatment of leachate is a highly efficient alternative. This process takes place in tanks with aerobic and anaerobic microorganisms that feed on organic compounds, transforming the decomposed organic matter into fertilizer. Heavy metals are removed by oxygenation.

Biochemical treatment

This type of treatment involves the use of plants as depolluting agents for contaminated materials and resources. Biochemical barriers are used in order to remove, isolate and degrade toxic substances contained in the leachate. Despite being a relatively simple treatment, it is necessary to select the type of plant used. In addition, the liquid needs to undergo further treatment to be reused.

landfill

Sanitary landfills are controlled places for depositing and treating garbage. In them, the slurry is collected through the installation of a drainage system that makes the soil waterproof. Once collected, it is sent to the tanks used in biological treatment, where heavy metals are retained, so that the water can return unpolluted to the environment.

Conclusion

The production of slurry is one of the biggest problems faced by large urban centers. Therefore, it is important to reduce the amount of waste generated and purchase a composter to transform organic matter into humus. In addition, dumps need to be replaced by controlled sanitary landfills, where the slurry naturally produced by the accumulation of organic matter can be treated and relocated.