Lecture (5): Waste treatment and disposal

Lecture (5): Waste treatment and disposal Lecture (4): Lecture objectives: By the end of this lecture students should be able to: To know the methods of reducing waste. To know the integrated waste management. To know the roads conservation.

Lecture (5) Topic No (1): Waste treatment and disposal by healthy burial. Common method of solid waste disposal. Landfills are the oldest methods of waste disposal in the world. The versatility and simplicity of it in terms of technical requirements, environmental and socio-economic aspects.

landfilling can be considered as the cheapest method to run. landfilling is expensive or comparable to other methods due to government policy and availability of land.

Production Of Landfill Gas: Landfill gas is produced during the natural breakdown of biodegradable waste. The composition of landfill gas changes over time. The gas from a typical landfill site consists mostly of methane and carbon dioxide.

LANDFILL FIRES As waste decomposes it generates heat and underground fires may start. These are difficult to extinguish, may last for long periods, and may spread throughout the landfill.

LANDFILL DESIGN Modern landfills are designed to minimize these problems: Location Landfill Liner Compaction of waste Daily Cover Landfill Cap Leachate Management System Landfill Gas management System

When landfill is full, layers of soil and clay seal in trash Topsoil Sand Electricity generator building Clay Leachate treatment system Garbage Methane storage and compressor building Probes to detect methane leaks Pipes collect explosive methane for use as fuel to generate electricity Methane gas recovery well Leachate storage tank Compacted solid waste Figure 21.15 Solutions: state-of-the-art sanitary landfill, which is designed to eliminate or minimize environmental problems that plague older landfills. Since 1997, only modern sanitary landfills are allowed in the United States. As a result, many small, older local landfills have been closed and replaced with larger regional landfills. Question: How do you think sanitary landfills could develop leaks of toxic liquids? Leachate pipes Groundwater monitoring well Leachate pumped up to storage tank for safe disposal Garbage Sand Synthetic liner Leachate monitoring well Sand Groundwater Clay and plastic lining to prevent leaks; pipes collect leachate from bottom of landfill Clay Subsoil

Site considerations: Is located in a geologically stable area Is not located on a major aquifer; Is not located in a vulnerable area; Is designed to reduce the risk of damage to the environment and human health; Will be monitored regularly for the duration of operations and aftercare period

Air pollution from toxic gases and trucks Sanitary Landfills Disadvantages Advantages No open burning Noise and traffic Dust Little odor Air pollution from toxic gases and trucks Low groundwater pollution if sited properly Releases greenhouse gases (methane and CO2) unless they are collected Can be built quickly Low operating costs Slow decomposition of wastes Figure 21.16 Advantages and disadvantages of using sanitary landfills to dispose of solid waste (Concept 21-4). Question: Which single advantage and which single disadvantage do you think are the most important? Why? Can handle large amounts of waste Output approach that encourages waste production Filled land can be used for other purposes Eventually leaks and can contaminate groundwater No shortage of landfill space in many areas Fig. 21-16, p. 576

Topic No (2): Waste treatment and disposal by biological analysis fertilization. biological methods, composting and anaerobic fermentation are the most common process in using, while due to the odour emission and low treatment capacity, composting is not so popular as anaerobic fermentation.

Is a natural bio-degradation process that takes organic wastes turns into nutrient rich food. Allowing organic materials to sit in one place for months until microbes decompose it. Is one of the best method of waste disposal. Turn unsafe organic products into safe compost. It is slow process and takes lot of space.

Topic No (3): Waste treatment and disposal by incineration. Is a type disposal method in which municipal solid wastes are burned at high temperatures Convert waste into residue and gaseous products. Reduce the volume of solid waste to 20 to 30 percent of the original volume, Decreases the space they take up and reduce the stress on landfills. This process is also known as thermal treatment

Incineration, Advantages and Disadvantages

Solutions: A Waste-to-Energy Incinerator with Pollution Controls