Liquid Waste Disposal Common Methods & Safer Alternatives

Wastewater and liquid wastes are constantly released from residential sources in the form of blackwater, or wastewater from toilets, and greywater from non-residential commercial sources such as commercial spaces, industries and hospitals. Wastewater and stormwater contain a surprising amount of pollutants that can affect the quality of life of humans and animals, as well as the environment.

Liquid waste from department stores, pharmaceutical and drug companies, hospitals, manufacturing plants, and other commercial bodies have the potential to negatively impact public health, plant and animal ecosystems, the local economy, as well as residential and commercial development.

It is the responsibility of industries producing liquid waste as well as the government and regulatory bodies to treat waste effectively and minimise the damage to the environment.

Common Methods of Liquid Waste Disposal

Some of the commonly followed methods of liquid waste disposal are:

Dewatering

• In this process, the water from the liquid waste is removed until only solid waste remains. The solid waste is then disposed of, while the water can be recycled and used again.
• This disposal technique is suitable only for non-hazardous liquid wastes.
• For physically distinguishable components of the liquid waste, centrifugation can be used to separate the solid contaminants from the liquid using the principle of density difference.  
• Sludges and slurry wastes can be filtered out using belt filter presses that separate water from the sludge with the help of gravity and accumulate the remaining sludge in a trough. This sludge is then pressed between a pair of filters so as to force out any remaining water using the pressure from two rollers.
• Dewatering is commonly used for liquid waste disposal in the construction industry.

Sedimentation

• This process is also suitable only for non-hazardous liquid wastes. It is often the initial step in municipal sewage water treatment and waste disposal.
• Sedimentation is a simple process that doesn’t require high-end equipment. It makes use of gravity to separate the solid wastes from the liquid.
• The liquid is left undisturbed in a large tank called a sedimentation basin, where the solid waste settles down due to the difference in density, while the lower density contaminants such as oil and grease rise to the top.
• Once this process is completed, the wastes are carefully removed and the water can be recycled further for usage, while the wastes can be safely disposed of.

Incineration

• Incineration can be used for the disposal of hazardous waste such as chemicals, scrap metals, acids and bases in water and liquids.
• In this process, the liquid waste is incinerated in combustion chambers at extremely high temperatures, creating hot gases and ashes. The ash residue can be discarded while the gases can undergo treatment and be let out into the environment. The heat energy from the gases can also be extracted for domestic or industrial use, such as cooking or supplying power to turbines. The water that is left behind is free of contaminants and suitable for usage.

Root Zone

• The root zone waste treatment method is primarily used for residential wastes such as the water that comes from bathrooms, kitchens and sinks.
• This waste disposal method uses both biological and physical processes for the treatment of water. It is slightly complicated and expensive but recycles the water completely, making it safe to be released into the environment again.
• The water undergoes treatment in various stages- pre-treatment in a settler, first treatment in an anaerobic baffled reactor, second treatment in an anaerobic filter, and third treatment in a planted gravel filter.
• Root zone method requires minimal external energy since it majorly depends on gravity. It also doesn’t require regular maintenance.

Composting

• Composting involves the use of microbes for the decomposition of organic wastes present in liquids by keeping them in a pit for a long period of time.
• Organic wastes contain nutrients such as nitrogen, sodium, and potassium, which can be extremely beneficial for the soil and the environment.
• Once the water is removed, the solid waste can be converted into compost, while the water can undergo proper recycling and be reintroduced into the environment.  
• The microbes present in the composting pit can metabolise solid organic wastes and reduce their volume by as much as 50 percent.
• This is an extremely environmentally friendly waste disposal method.

Solidification

• With this process, liquid waste disposal companies can conveniently turn liquid waste into solid waste without increasing its volume by adding bulking agents such as fly ash, sawdust, or lime dust.
• While solidification is an environmentally safe alternative to the harmful underground injection method, it does increase greenhouse gas emissions, depending on the type of bulking reagent used.
• It is also expensive since it involves the transportation of a large number of solid wastes.

The Need for Liquid Waste Disposal & Safer Alternatives

The United States generates about 267.8 million tons of waste every year, out of which approximately 32.5 percent is recycled or composted, 12.5 percent is incinerated, and the remaining 55 percent is buried in landfills.

The traditional methods of liquid waste disposal raise a problem – the filling up of landfills. Since most treatment methods involve the disposal of solid waste from water and other liquids at landfills, there is a high and inevitable possibility of all the space in landfills being completely used up. It is projected that in 2050, about 3.4 billion metric tons of municipal solid waste will be generated around the world. This would pose a great environmental concern if the landfills ran out of space.

Governments and industries need to be conscious of the environment and their impact on it. Even though the most popular form of waste disposal is landfilling, there are many environmentally friendly, efficient, easy, and cost-effective alternative waste management and disposal solutions that businesses and industries can switch to.

Businesses need to begin composting organic waste, recycling, and reusing their materials to reduce the amount of waste discarded at landfills. Many materials that are sent to landfills are actually reusable and recyclable. Though some of these processes may be expensive, they have long term benefits.

Some safe alternatives to landfilling are:

• Composting: conversion of organic waste into nutrient-rich compost for soil and plants
• Biological reprocessing: speeding up the natural decomposition of organic matter and using the methane generated in the process as a source of energy (for producing heat and electricity).
• Waste to Energy (WtE): generating heat, fuel, or electricity from non-recyclable waste materials and using that energy as an alternative to fossil fuels.
• Bioremediation: converting hazardous waste into non-hazardous waste with the help of environment-friendly microbes.
• Plasma gasification: using highly ionised or electrically charged gases called plasma inside a vessel to convert carbon-based wastes into useful and environmentally clean fuel.

Conclusion

The world is moving towards greener and innovative methods of waste disposal and reducing toxic emissions from conventional waste disposal methods to become environmentally responsible.

If treated inadequately, liquid wastes and wastewater pose huge threats to lives as well as the environment. All of the wastewater generated by residential spaces, farms, businesses, factories, and industries, and other commercial spaces eventually returns to the environment to be reused. So, proactive waste disposal strategies can help ensure liquids containing wastes are properly treated before being they are released into the environment.