Sustainable Environmental Engineering

10Recovery

No material is wasted in a functioning ecosystem.

OBJECTIVES

• To understand that water is the most valuable product to be recovered
• To explain that traditional tertiary treatment of removing N and P from wastewater is expensive and unsustainable
• To recover nutrients, energy, and water (NEW) from wastewater by designing WRRFs
• To understand the struvite precipitation mechanism and process
• To provide capital and operation and maintenance (O&M) cost equations for decision making on water, energy, and nutrient recovery
• To design a cost‐effective system to reclaim water to the required discharge standards

10.1 Principle 7

The degree of recovering water, energy, nutrient, and materials from wastewater (WW) reflects the sustainable level in EEIS design. In theory, almost all the wastewater (WW) could be recovered to reusable water because contaminants in WW is less than 0.1% by weight. However, not all the water could be recovered because water used in economy tend to dissipate within the economic system due to the second law of thermodynamics. In addition, energy resources are usually not recyclable. Energy would deteriorate to lower grade energy in addition to dissipation in the environments. Indeed, entropy would put a limit in designing recovery processes of EEIS. This irreversible energy degradation rate depends upon not only the ratio between the intensities of output and input flows but also the energy quality. Therefore, the ultimate decision whether to recover ...