Options for the Disposal and Reuse of Wastewater Sludge, Associated Benefit, and Environmental Risk

*Astha Kumari, Nityanand Singh Maurya, Abhishek Kumar, Rajanee Kant Yadav and Amit Kumar*

### **Abstract**

To protect human and environmental health, wastewater treatment is one of the important activities in urban and industrial areas. Urbanized increasing population with industrialization demands more amount of wastewater treatment. Despite wastewater treatment's positive impact on human and environmental health, it also produces sludge as a by-product of the process. Characteristics of the sludge mainly depend on the source of wastewater and the process applied for its treatment. Domestic sludge generally contains a large number of pathogenic bacteria carrying biodegradable compounds. Characteristics of industrial sludge vary greatly. It may contain biodegradable, non-biodegradable, toxic compounds, heavy metals, etc. The sludge may be in the form of liquid or semisolid with 0.25–12% solids. Thus, the handling and disposal/reuse of sludge may become a complex task due to its large volume and infectious and/or toxic nature. This chapter analyses the characterization and quantity estimate of the sludge produced during the application of various municipal and industrial wastewater treatment options. Current practices for the disposal and reuse options such as anaerobic digestion for biogas production, composting to utilize as a fertilizer, brick production, filler material, and bioplastic production will be reviewed and the suitability of each option in terms of benefit and risk will be critically analyzed.

**Keywords:** sewage sludge, biogas, bioplastic, anaerobic digestion, sludge reuses

#### **1. Introduction**

Wastewater contains a lot of solid and liquid waste discarded after use and defined in various combinations based on their sources of generation. The wastewaters from residential apartments, colonies, and institutions are termed domestic, wastes from agricultural fields, mining effluents and industrial are termed as industrial wastewater [1].

With the increase in population coupled with urbanization and industrialization, the quantity of wastewater is also increasing. To cater to the increasing demand for water for urban, industrial, and agricultural purposes, the need for its treatment,

call for water reuse, and resource recovery are growing exponentially. Wastewater treatment is one of the important activities in urban and industrial areas in order to protect human and environmental health and to eliminate or neutralize these pollutants. Though wastewater treatment has a positive impact on human and environmental health, it also produces sludge as by-product of the process. The sludge may be in the form of a liquid or a semisolid, with 0.25 to 12% solids that come from households and industries [2]. This sewage sludge may cause various environmental and health problems such as nutrient leaching, loss of soil biodiversity, emission of GHGs, and pathogenic outbreak [2]. Challenges related to managing the sludge thus produced are cost related to handling and transportation, disposal methods, strict regulations, and environmental threats [3]. A clean and sustainable environment can only be built by introducing technologies that are environment friendly and economically feasible. Hence, the treatment of wastewater as per quality standards is no longer the only objective of WWTPs; they also need to focus on its discharge management units. Sewage sludge contains insecticides, cleansing agent, oils, fats, grease, thinners, paints, etc. The high fat content of the sludge may be utilized for biofuel productions such as biodiesel, biohydrogen, bioethanol, and bio-oils [4].

Therefore, the chapter will include the characterization and quantity estimate of the sludge produced during the application of various municipal and industrial wastewater treatment options. Current practices for disposal and reuse options such as anaerobic digestion for biogas production, composting to utilize as fertilizer, brick production, filler materials, or bioplastic production will be reviewed, and the suitability of each option in terms of benefit and risk will be critically analyzed.
