Report on the Optimization of Immobilized Activated Sludge for Cellulose Industry Wastewater Treatment

Executive Summary

The cellulose industry’s significant water consumption and subsequent generation of highly polluted wastewater present a critical challenge to environmental sustainability, directly impacting the achievement of Sustainable Development Goal 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production). This report details a study aimed at developing an innovative and efficient bioremediation strategy to address this issue. The performance of activated sludge was evaluated in both freely suspended and immobilized systems. Using an electrospray technique, microbial cells were immobilized in alginate and hybrid alginate-polyvinyl alcohol microbeads. A Response Surface Methodology (RSM) was employed to optimize the process variables, including electrospray voltage and cell-polymer suspension volume. The results demonstrated that immobilized cells significantly outperform free cells. The optimized process, using alginate-immobilized cells, achieved a 74% reduction in Chemical Oxygen Demand (COD), from an initial 6715 mg/L to 1736 mg/L over four days. This outcome represents a significant advancement in sustainable industrial wastewater management, contributing to SDG 9 (Industry, Innovation, and Infrastructure) by providing a technologically advanced solution to mitigate industrial pollution.

Introduction: Aligning Industrial Processes with Sustainable Development Goals

The Challenge of Industrial Wastewater in the Cellulose Sector

The pulp and paper manufacturing sector is a major contributor to industrial water pollution. The effluent from this industry is characterized by high levels of pollutants, which poses a significant threat to environmental health and complicates efforts to achieve key Sustainable Development Goals.

• SDG 6 (Clean Water and Sanitation): The discharge of untreated or inadequately treated wastewater, with high Chemical Oxygen Demand (COD), suspended solids, and turbidity, directly degrades the quality of freshwater bodies.
• SDG 14 (Life Below Water): The influx of these pollutants into aquatic ecosystems harms marine and coastal life, disrupting ecological balance.
• SDG 12 (Responsible Consumption and Production): The industry’s large water footprint and pollutant output underscore the urgent need for more sustainable production patterns that minimize environmental impact.

Innovative Solutions for Sustainable Industrial Infrastructure

To address these challenges, this study explores advanced biological treatment methods as a cornerstone of sustainable industrial practice, in line with SDG 9 (Industry, Innovation, and Infrastructure). While conventional biological treatments are effective, their performance can be hindered by toxins present in industrial wastewater. Cell immobilization, a technique where microbial cells are entrapped within a protective polymer matrix, offers a robust solution by enhancing microbial resilience and treatment efficiency. This research focuses on optimizing an electrospray technique for creating microbeads to immobilize activated sludge, aiming to develop a highly effective and scalable solution for the cellulose industry.

Methodological Framework for Enhanced Bioremediation

Experimental Design and Materials

The methodology was designed to systematically evaluate and optimize the performance of immobilized activated sludge for treating high-strength cellulose wastewater.

1. Wastewater and Microorganisms: Effluent and activated sludge were collected from a cellulose production facility. The initial wastewater was characterized by a COD of 6715 mg/L, turbidity of 950 NTU, and Total Suspended Solids (TSS) of 7400 mg/L.
2. Immobilization Carriers: Two types of carriers were investigated to support the microbial cells:
   • A natural polymer: Alginate (1% w/w)
   • A hybrid polymer: Alginate-Polyvinyl Alcohol (PVA)

Immobilization Process and Optimization

A modern electrospray technique was utilized to produce microbeads, allowing for control over particle size, which is critical for mass transfer efficiency. The process was statistically optimized using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The primary variables investigated were:

• Electrospray Voltage (0–12 kV)
• Volume of Cell-Polymer Suspension (1–3 mL)
• Type of Polymer Carrier

Performance Evaluation

The effectiveness of the treatment was quantified by measuring the reduction in Chemical Oxygen Demand (COD). This metric serves as a direct indicator of the decrease in organic pollution load, providing a clear measure of progress toward the water quality targets of SDG 6.

Analysis of Results and Contribution to SDGs

Comparative Performance of Treatment Systems

The study confirmed the superior efficacy of cell immobilization. While the freely suspended activated sludge system achieved a 65% COD removal in four days, the immobilized system demonstrated a higher potential, with a maximum removal of 78% under certain conditions. This enhancement underscores the value of investing in innovative industrial technologies, a key target of SDG 9, to achieve superior environmental outcomes.

Optimization of the Immobilized Cell System

Statistical optimization identified the ideal conditions for maximizing wastewater bioremediation. The highest performance was achieved with the following parameters:

• Maximum COD Removal: 74% (a reduction from 6715 mg/L to 1736 mg/L).
• Optimal Carrier: Alginate polymer.
• Optimal Electrospray Voltage: 3 kV.
• Optimal Suspension Volume: 2.5 mL.

This result provides a validated, high-efficiency framework for treating cellulose industry wastewater, directly supporting the goal of halving the proportion of untreated wastewater as per SDG 6.3.

Key Factors Influencing Treatment Efficiency

The analysis of variance (ANOVA) revealed that the interaction between electrospray voltage and the volume of the cell-polymer suspension was the most significant factor influencing COD removal. This indicates that reducing microbead size (by increasing voltage) is most effective when the concentration of microbial cells is sufficient. Furthermore, the alginate carrier consistently outperformed the hybrid alginate-PVA matrix, suggesting that natural, biodegradable polymers can be highly effective for this application, aligning with the principles of sustainable production under SDG 12.

Conclusion and Implications for Sustainable Development

This research successfully demonstrates that an optimized immobilized cell system, fabricated using an electrospray technique, is a highly effective method for treating high-strength wastewater from the cellulose industry. The achievement of 74% COD removal highlights a viable technological pathway for industries to significantly reduce their environmental footprint.

The findings of this report make a direct and measurable contribution to several Sustainable Development Goals:

• SDG 6 (Clean Water and Sanitation): The technology provides a robust solution for improving water quality by effectively treating industrial effluent before discharge.
• SDG 9 (Industry, Innovation, and Infrastructure): The study advances an innovative and efficient technology that promotes sustainable industrialization.
• SDG 12 (Responsible Consumption and Production): The optimized process enables a more sustainable production model for the cellulose industry, reducing pollution and promoting the use of biodegradable materials.
• SDG 14 (Life Below Water): By drastically reducing the pollutant load in industrial wastewater, this method helps prevent the degradation of aquatic ecosystems.

Analysis of Sustainable Development Goals (SDGs) in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The article on treating wastewater from the cellulose industry connects to several Sustainable Development Goals (SDGs) by addressing issues of water pollution, industrial sustainability, and environmental protection. The primary SDGs identified are:

• SDG 6: Clean Water and Sanitation
• SDG 9: Industry, Innovation, and Infrastructure
• SDG 12: Responsible Consumption and Production
• SDG 14: Life Below Water

2. What specific targets under those SDGs can be identified based on the article’s content?

Based on the article’s focus on treating polluted industrial wastewater using innovative biological methods, the following specific targets are relevant:

1. SDG 6: Clean Water and Sanitation

   • Target 6.3: By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.
     
     Explanation: The article directly addresses this target by investigating an efficient method for treating “highly polluted wastewater” from the cellulose industry. The study’s main goal is to reduce pollutants, specifically the “chemical oxygen demand (COD), suspended solids and high turbidity,” thereby improving the quality of the water before it is discharged.

2. SDG 9: Industry, Innovation, and Infrastructure

   • Target 9.4: By 2030, upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes.
     
     Explanation: The research focuses on developing and optimizing an innovative and environmentally sound technology—”immobilized activated sludge” using an “electrospray technique”—to manage industrial waste. This represents an effort to make the cellulose industry’s production process more sustainable by improving its wastewater treatment capabilities.

3. SDG 12: Responsible Consumption and Production

   • Target 12.4: By 2020, achieve the environmentally sound management of chemicals and all wastes throughout their life cycle… and significantly reduce their release to air, water and soil in order to minimize their adverse impacts on human health and the environment.
     
     Explanation: The article highlights that the “abundant use of cellulose industry products has led to an increase in production” and the “vast consumption of chemicals” results in polluted wastewater. The study’s method for treating this wastewater is a direct contribution to the environmentally sound management of industrial waste and chemicals, reducing their release into water bodies.

4. SDG 14: Life Below Water

   • Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution.
     
     Explanation: Industrial wastewater from land-based activities like the cellulose industry is a major source of pollution for rivers and, ultimately, oceans. By developing a method that achieves “maximum biodegradation and COD removal of 74%,” the study contributes to preventing the discharge of harmful pollutants that would otherwise degrade aquatic ecosystems.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, the article explicitly mentions and implies several quantitative indicators that can be used to measure progress towards the identified targets.

1. Indicators for Target 6.3 (Improve water quality)

   • Chemical Oxygen Demand (COD) Level: This is the primary indicator used throughout the study. The article quantifies the initial pollution level (6715 mg/L) and the level after treatment (1736 mg/L), providing a direct measure of water quality improvement.
   • COD Removal Percentage: The study reports a “maximum biodegradation and COD removal of 74%,” which serves as a key performance indicator for the effectiveness of the wastewater treatment process.
   • Turbidity and Total Suspended Solids (TSS): The article mentions the initial high levels of “turbidity (950 NTU)” and “total suspended solids (TSS) (7400 mg/L)” as key problems. These serve as baseline indicators against which the success of treatment methods can be measured.

2. Indicators for Target 9.4 (Adoption of clean technologies)

   • Efficiency of an Innovative Technology: The success of the “electrospray technique” and “immobilized sludge” method, measured by the 74% COD removal, serves as an indicator of the successful adoption and performance of a cleaner, more environmentally sound technology in an industrial context.

3. Indicators for Target 12.4 (Sound management of waste)

   • Reduction in Pollutant Concentration: The measured decrease in COD from 6715 mg/L to 1736 mg/L is a direct indicator of the reduction of chemical waste released into the environment, demonstrating progress in the sound management of industrial effluent.

4. Indicators for Target 14.1 (Reduce land-based pollution)

   • Reduction of Organic Pollutants (measured by COD): High COD levels in discharged water lead to oxygen depletion in aquatic environments, a major form of water pollution. The significant reduction in COD is an implied indicator of preventing pollution that would harm life below water.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com