What are the biological processes of solid waste treatment?

Biological solid waste includes bacterial and contaminated waste produced by living individuals. Its treatment is essential to prevent the spread of any air-borne or water-borne diseases or diseases transmitted from one organism to another in a food chain. There are many benefits of the biological solid waste treatment and some of them are: the minimized quantity of waste substance, waste control, eradicating any disease-causing pathogens, generation of biogas, composting, anaerobic digestion, bio drying, mechanical biological treatment, microbial fuel cell, phytoremediation, and biofiltration. The final products of the biological solid waste treatment may be recycled to obtain organic fertilizers or disposed of in SWDS (Solid Waste Disposal Site) after proper treatment.

The 3R’s for biological solid waste management 

Reduce, Reuse and Recycle are the 3R’s useful for a systematic solid waste management system.

Reduce

Minimizing waste produced by every person will drastically reduce the waste content. It can be simply managed by purchasing only what is required and preventing unnecessary excess wastage. Product packaging is one of the major causes of an increase in landfill waste and hence minimize using materials with extensive packaging and avoid buying products with unnecessary extra protection or covering of plastic. One can opt for bulk purchasing of goods and avoid disposable items and make a habit of using durable items.

Reuse

Many items can be used again like packets of certain items if stored carefully. They save plenty of money by reusing such packets. Instead of disposable products, use durable items that can be used several times before disposing of them. There are ample upcycling ideas on the internet which are DIY (Do It Yourself) things super handy to use and easy to make. Many goods can be second-hand and one can donate them which may be useful for the people who need it urgently or can’t afford the same brand-new item.

Recycle

Products that are already used undergo a recycling process which makes them reusable yet again. For instance, a paper once used can be recycled and made into a new one for writing anything else. Even plastic, which takes hundreds of years to decompose, is recycled for using it again and avoiding harm to the environment. Several recycling units accept certain items in a particular condition and some give back the money, coupons, or discounts in exchange for these used items.

Bio-Covers of landfills 

A huge section of untreated municipal solid waste finally paves its path to the landfills, normally considered as a dumping ground. It comprises a variety of energy resources like landfill gases (LFG) and fine soil grains. These energy materials can be useful for many purposes like the gases can be preserved inside a container and used for fuel or biogas and the fine soil materials of very old landfills may act as a cover material for different landfills or may be required as a soil conditioner.

Composting and its benefits

Composting is the alteration of organic matter (mostly kitchen waste) to organic fertilizer useful as a plant nutrient by decomposing the combination of organic matter, soil and twigs, dry leaves, and so on for obtaining the ultimate product as compost. Earthworms and insects inside soil assist in this decomposition. The steps in the process of composting include waste collection, unloading in the compost-making area, shredding, loading, pathogen disinfection, unloading, and sending to maturation unit, screening, finishing compost, and filling in finished bags.

The composting procedure needs creating a pile of wet organic matter (green waste) and the materials shall break down eventually into humus after keeping it for weeks or months. Since conventional composting consumes a lot of time, modern composting is a closely inspected monitored process with the addition of water, air, substances rich in carbon and nitrogen. The process of decomposition is done by further shredding the matter and guaranteeing proper aeration along by frequently rotating the container in which the mixture is prepared. Fungi and worms are either born inside or additionally transferred to the mixture and aerobic bacteria for transforming the matter into CO₂, NH₄, and heat. This NH₄ is not directly absorbed by plants, rather the plants convert it to nitrates, and then it gets directly absorbed by them.

Applications of composting are in horticulture, agriculture, natural fertilizer for plants or saplings, erosion control, landfill cover, stream reclamation, and wetland construction.

Anaerobic digestion

Anaerobic Digestion is termed as the procedure in which micro-organisms break down the organic biodegradable material in the absence of oxygen. Fermentation required in large industries for the creation of food uses anaerobic digestion. The steps include hydrolysis, fermentation, acetogenesis, and methanogenesis.

Applications of anaerobic digestion are cooking gas, fuel, soil conditioner, electricity production, minimizing landfill gas emission in the air, and wastewater treatment.

Bio-Drying of solid waste 

Bio-drying is defined as the procedure through which the biodegradable waste is quickly ignited during the first stages of composting for eradicating humidity from the waste and reducing the overall weight and quantity. The main part of the heat is used to evaporate surface water-related with the amalgamation of sludge. This heat production helps in minimizing the moisture content of biomass without any fossil fuels and very little power consumption. It takes 8 days to dry the waste and reduces disposal costs.

Mechanical biological treatment (MBT)

It is a system for processing waste by mixing a sorting facility along with a biological treatment form like anaerobic or composting. They are constructed to process mixed types of waste like a commercial, household, or industrial. This particular system recovers the materials inside the combined waste to generate refuse-derived fuel which is used for electricity production. Steps include mechanical sorting and then biological processing.

Uses of MBT are in renewable (biogas) fuel, finding recyclable materials like metals, paper, plastic, and so on, and digestate (organic soil improver).

Microbial fuel cell (MFC) (Biological fuel cell)

It is a bio-electrochemical system that creates electric current by utilizing bacteria and imitating the bacterial processes in nature. Useful for the treatment of wastewater and acts as a plant microbial fuel cell.

Biofiltration

It is used as a pollution modulation methodology by placing a bioreactor that comprises living substances to catch and degrade pollutants. It captures harmful chemicals, wastewater processing, and so on.

The procedure includes using a biofilter made of micro-organisms attached to it and creating a biofilm. The water to be treated is poured to and fro over the medium. The biofilter consists of phases such as solid, liquid, and gaseous phases. The elements and matter diffuse onto the film by biodegradation. Biofiltration being an aerobic process needs oxygen supply which is given by the flow of water.

Context and Application

• Bachelors of Technology (Civil Engineering)
• Masters of Science (Hydraulic Engineering)
• Masters of Science (Environmental Engineering)
• Masters of Science (Solid Waste Management)

Practice Problems

Q1. What are the 3 R's for biological solid waste treatment? (In chronological order)

1. Reduce, Reuse Recycle
2. Reuse, Reduce, Recycle
3. Recycle, Reuse, Reduce
4. Reduce, Recycle, Reuse

Correct Option: a

Explanation: The 3 R’s for biological solid waste treatment in chronological order are Reduce, Reuse and Recycle.

Q 2. What is the full form of MBT?

1. Mechanical Bean Terminology
2. Mechanical Biological Treatment
3. Matter Biological Terminology
4. Mechanical Book Terminology

Correct Option: b

Explanation: The full form of MBT is Mechanical Biological Treatment.

Q 3. What type of process is used in biofiltration?

1. Anaerobic
2. Distillation
3. Aerobic
4. Destruction

Correct Option: c

Explanation: Aerobic type of process is used in biofiltration

Q 4. Where is the composting technique used?

1. Production of digestate
2. Welding
3. Separation of solid and wet waste
4. Horticulture and agriculture

Correct Option: d

Explanation: The composting technique used in horticulture and agriculture.

Q 5. Which process is used for heating the waste to remove moisture content and eventually reduce the overall waste?

1. Bio-drying
2. Biofiltration
3. Composting
4. Phytoremediation

Correct Option: a

Explanation: Bio-drying process is used for heating the waste to remove moisture content and eventually reduce the overall waste.

Related Concepts

• Petroleum Hydrocarbon Treatment
• Heavy Metal Immobilization due to biological processing
• Mining of solid waste
• Global warming and greenhouse gas effect