With over 1.4 billion people, rapid urbanization and industrial growth are putting massive pressure on India’s water resources and environmental systems. Managing wastewater isn’t just about keeping cities clean or protecting public health; it’s a huge opportunity to recover valuable resources. Modern wastewater treatment plants are no longer just waste disposal units; they are becoming centers for reclaiming water, generating energy, and producing nutrient-rich materials that support a circular economy.
This guide walks you through the key byproducts of wastewater treatment, including treated water, biogas, and wastewater sludge management, and explains their importance in India’s context. We’ll also highlight the challenges, especially with industrial wastewater, and the role organizations like the Central Pollution Control Board (CPCB) play in ensuring proper management. By the end, you’ll see that wastewater is far more than something to get rid of; it’s a resource waiting to be used.
Wastewater treatment is a multi-step process designed to remove solids and pollutants from water. Each step generates specific byproducts that need careful management but also offer chances to recover resources.
The primary goal of a sewage treatment plant (STP) is to clean wastewater, but the treated water that comes out is one of the most useful byproducts. Once cleaned of harmful substances and pathogens, this water can be safely reused, which is a game-changer in a country facing frequent water shortages.
The Central Pollution Control Board (CPCB) sets strict rules for treated water. Parameters like Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS) must meet specified limits before the water can be discharged or reused.
Where Treated Water Makes a Difference:
However, many STPs in India aren’t operated properly or maintained well, resulting in underutilization of treated water. This calls for better infrastructure and tighter enforcement of regulations to ensure the potential of treated water is fully realized.
Sludge is the leftover material from the treatment process. It’s a mix of solids, biomass, and other substances that settle out during preliminary and biological treatments. Managing sludge accounts for as much as 65% of an STP’s operating cost.
According to industry reports, 80–90% of STPs in India don’t treat sludge properly. Instead, they simply dewater it to reduce its volume and dump it, which creates environmental hazards. Untreated sludge can contain pathogens, heavy metals, and toxins that pose risks to soil and water.
Turning Sludge into Biosolids:
For sludge to be safely reused, it must go through stabilization, usually via anaerobic digestion. Microorganisms break down organic material in the absence of oxygen, which reduces pathogens and produces biogas.
After digestion, the sludge is dewatered and processed into biosolids. CPCB guidelines classify biosolids based on safety:
Biosolids are rich in nitrogen, phosphorus, and micronutrients, making them ideal for agriculture. Using biosolids as fertilizers can improve soil health, boost crop yields, and close nutrient loops, offering a sustainable alternative to chemical fertilizers. This is an important aspect of wastewater sludge management in India and globally, providing a viable solution to reduce waste and enhance agricultural productivity.
Biogas is a valuable byproduct of sludge treatment. It’s primarily composed of methane, the same component used in natural gas, and is produced during the anaerobic digestion process.
A successful example is the Surat Municipal Corporation’s (SMC) Anjana STP in Gujarat. SMC set up India’s first municipal biogas-based power plant, with a capacity of 0.5 MWe. It converts liquid waste into electricity, reducing reliance on the grid and cutting monthly electricity expenses by ₹3 to ₹3.5 Lakhs.
The Benefits of Biogas:
Biogas is becoming a key piece in India’s push toward renewable energy and sustainable development.
Industrial wastewater brings its own challenges and opportunities. Different sectors—textiles, chemicals, pharmaceuticals—produce wastewater with specific pollutants like dyes, heavy metals, and complex chemicals.
The Delhi High Court recently pointed out that untreated industrial wastewater is often mixed with domestic sewage, undermining treatment efforts and raising serious environmental concerns. Industries must invest in better treatment systems to prevent this from happening.
Understanding how a treatment plant operates helps explain how byproducts are created and recovered.
The components of a wastewater treatment plant include:
India’s approach to wastewater is evolving with stricter regulations and a growing focus on resource recovery. Wastewater treatment is shifting from disposal to reclaiming clean water, generating energy, and supporting agriculture and industry.
Wipro Water is leading the way in industrial wastewater treatment, promoting sustainable practices like Zero Liquid Discharge and energy-efficient technologies to help achieve India’s sustainability goals.
The main byproducts of wastewater treatment include treated water (effluent), wastewater sludge, and biogas. Treated water can be reused in agriculture, industry, and for groundwater recharge. Wastewater sludge can be turned into biosolids, which are useful as fertilizers, while biogas can be used to generate energy.
Biogas is a byproduct of anaerobic digestion of sludge, primarily composed of methane. It can be used as a renewable energy source to power wastewater treatment plants, reducing energy costs and carbon emissions. It can also be used to generate electricity or as a fuel for local grids or vehicles.
Improper wastewater treatment can lead to contamination of soil and water bodies with pathogens, heavy metals, and toxic chemicals. This can harm aquatic ecosystems, damage soil health, and pose serious risks to public health, particularly in areas with inadequate treatment infrastructure.
Advanced treatment technologies, such as membrane filtration and chemical recovery processes, help industries extract valuable chemicals, reduce pollutants, and recycle water. These systems support Zero Liquid Discharge (ZLD) practices, ensuring that wastewater is treated and reused with minimal environmental impact.