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Chapter 20: Problem 7

Name and describe three methods of treating raw sludge, and give the end product(s) that may be produced from each method.

Short Answer

Expert verified
Three methods of treating raw sludge are: 1) Anaerobic Digestion, producing biogas and biosolids, 2) Composting, producing nutrient-rich soil-like product, and 3) Lime Stabilization, producing lime-stabilized sludge suitable for agricultural use.

Step by step solution

01

Method 1: Anaerobic Digestion

As the name indicates, it is a biological process that takes place without oxygen. With the help of bacteria, the organic matter in the sludge is broken down, producing biogas (a mix of methane and carbon dioxide) and biosolids. Biogas can be used for energy production, and biosolids can be used as fertilizer after further processing.
02

Method 2: Composting

Composting is decidedly a more natural method. Bacteria and fungi are involved in decomposing organic matter in the sludge. The result is a soil-like end product rich in nutrients, ideally utilized for land applications. However, because temperature conditions and degradation time that are specific to wastewater sludge, the method can be time-consuming.
03

Method 3: Lime Stabilization

Adding lime to sludge results in increased pH levels that make it harmful for pathogens. This makes it a popular option for treating sludge given its cost-effectiveness and efficacy. Its end product, lime-stabilized sludge, can be used directly for agricultural land spreading.

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