Wastewater treatment – Flow Rates, Pollutants, Purification – Britannica

Wastewater Treatment and Disposal: A Sustainable Development Perspective

Overview of Wastewater Treatment Systems

The design and capacity of wastewater treatment systems are influenced by the volume of sewage generated by residential, commercial, and industrial sources, as well as inflows and infiltration (I&I). The choice between on-lot, clustered, or centralized treatment plants depends on multiple factors:

1. Number of customers served
2. Geographical and site constraints
3. Sewer connections
4. Average and peak wastewater flows
5. Characteristics of influent wastewater
6. Regulatory effluent limits
7. Technological feasibility
8. Energy consumption
9. Operations and maintenance costs

Wastewater Disposal Methods and Public Health

In urban areas, the predominant method of wastewater disposal is discharge into surface water bodies, while suburban and rural areas often rely on subsurface disposal. Regardless of the method, wastewater must be treated to protect public health and maintain water quality, aligning with Sustainable Development Goal (SDG) 3: Good Health and Well-being, and SDG 6: Clean Water and Sanitation.

• Removal of suspended particulates and biodegradable organics
• Destruction of pathogenic bacteria
• Elimination of nitrates and phosphates to prevent eutrophication
• Neutralization or removal of industrial wastes and toxic chemicals

Regulatory Standards and Environmental Protection

The extent of wastewater treatment is governed by local environmental conditions and governmental standards, supporting SDG 14: Life Below Water, and SDG 15: Life on Land. Two key types of standards include:

• Stream Standards: Limit pollutants in natural water bodies to prevent water quality deterioration. Parameters regulated include dissolved oxygen, coliform bacteria, turbidity, acidity, and toxic substances.
• Effluent Standards: Control the quality of treated wastewater discharged from treatment plants, focusing on biochemical oxygen demand (BOD), suspended solids, acidity, and coliform bacteria.

Levels of Wastewater Treatment

Wastewater treatment is categorized into three levels, each contributing to the achievement of SDG 6 by improving water quality:

1. Primary Treatment: Removes approximately 60% of suspended solids and 35% of BOD; dissolved impurities remain untreated. Serves as the initial treatment step.
2. Secondary Treatment: Removes over 85% of suspended solids and BOD. This level is generally mandated in developed countries to ensure adequate water purification.
3. Tertiary (Advanced) Treatment: Applied when removal of more than 85% of solids and BOD is required, or when reducing dissolved nitrates and phosphates. Can eliminate over 99% of impurities, producing effluent close to drinking-water quality. Although costly, tertiary treatment is essential in sensitive environments.

Disinfection and Final Effluent Quality

Before discharge into surface waters, treated wastewater undergoes disinfection to eliminate remaining pathogens, thereby safeguarding public health (SDG 3) and aquatic ecosystems (SDG 14). Common disinfection methods include:

• Chlorination using chlorine gas or hypochlorite solutions with a minimum contact time of 15 minutes
• Dechlorination to mitigate adverse effects of chlorine residuals on aquatic life
• Ultraviolet (UV) radiation, an emerging alternative that disinfects without chemical residues

Conclusion: Advancing Sustainable Development Goals through Wastewater Management

Effective wastewater treatment and disposal are critical to achieving multiple Sustainable Development Goals, including:

• SDG 3: Ensuring healthy lives by preventing waterborne diseases
• SDG 6: Ensuring availability and sustainable management of water and sanitation for all
• SDG 11: Making cities inclusive, safe, resilient, and sustainable through proper sanitation infrastructure
• SDG 14 and 15: Protecting aquatic and terrestrial ecosystems by preventing pollution

Investment in advanced treatment technologies and adherence to regulatory standards are essential to protect public health, preserve environmental quality, and promote sustainable urban and rural development.

1. Sustainable Development Goals (SDGs) Addressed in the Article

1. SDG 6: Clean Water and Sanitation
   • The article discusses wastewater treatment and disposal, focusing on protecting public health and water quality.
   • It emphasizes the purification of wastewater to remove pollutants, pathogens, nitrates, phosphates, and toxic chemicals.
2. SDG 3: Good Health and Well-being
   • Protection of public health through disinfection of wastewater to destroy pathogens is highlighted.
3. SDG 11: Sustainable Cities and Communities
   • The article addresses wastewater management in urban, suburban, and rural areas, contributing to sustainable urban development.
4. SDG 12: Responsible Consumption and Production
   • It mentions the need to neutralize or remove industrial wastes and toxic chemicals, reflecting responsible management of chemicals and waste.
5. SDG 14: Life Below Water
   • Effluent and stream standards aim to prevent deterioration of water bodies, protecting aquatic life.

2. Specific Targets Under the Identified SDGs

1. SDG 6: Clean Water and Sanitation
   • Target 6.3: Improve water quality by reducing pollution, minimizing release of hazardous chemicals and materials, and substantially increasing recycling and safe reuse globally.
   • Target 6.1: Achieve universal and equitable access to safe and affordable drinking water.
2. SDG 3: Good Health and Well-being
   • Target 3.9: Reduce the number of deaths and illnesses from hazardous chemicals and air, water, and soil pollution and contamination.
3. SDG 11: Sustainable Cities and Communities
   • Target 11.6: Reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.
4. SDG 12: Responsible Consumption and Production
   • Target 12.4: Achieve environmentally sound management of chemicals and all wastes throughout their life cycle.
5. SDG 14: Life Below Water
   • Target 14.1: Prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities.

3. Indicators Mentioned or Implied in the Article to Measure Progress

1. Water Quality Parameters
   • Dissolved oxygen levels
   • Coliform bacteria counts
   • Turbidity
   • Acidity (pH levels)
   • Toxic substances concentration
2. Effluent Quality Indicators
   • Biochemical Oxygen Demand (BOD)
   • Suspended solids concentration
   • Pathogen levels (post-disinfection)
   • Nitrate and phosphate levels (nutrient removal)
   • Chlorine residuals in effluent
3. Wastewater Treatment Levels
   • Percentage removal of total suspended solids
   • Percentage removal of BOD
   • Effectiveness of primary, secondary, and tertiary treatment processes

4. Table: SDGs, Targets and Indicators

Source: britannica.com