In recent years, wastewater treatment has seen remarkable advancements, with innovative technologies surpassing traditional methods in both efficiency and effectiveness. These cutting-edge solutions are gaining traction among industries and governments due to their potential to ensure a sustainable supply of clean water. Advanced wastewater treatment encompasses a range of specialized techniques designed to address complex industrial challenges. For example, advanced oxidation processes (AOPs) effectively remove color and reduce chemical oxygen demand (COD) from textile mill effluents. Sequential anaerobic/aerobic biological treatments are highly effective in breaking down recalcitrant compounds found in wastewater from ammunition plants. Additionally, membrane technologies like ultrafiltration, nanofiltration, and reverse osmosis facilitate the separation and recovery of valuable organic solvents from mixed industrial waste streams. Electrochemical methods, including electrocoagulation and electrooxidation, efficiently remove heavy metals and organic pollutants, making them ideal for sectors such as mining and electronics. Meanwhile, biological nutrient removal (BNR) systems target nitrogen and phosphorus, helping industries meet stringent environmental regulations. These advanced methods not only enhance treatment performance but also support resource recovery, energy efficiency, and environmental sustainability, positioning industries to better address global water challenges and contribute to a more sustainable future.
A few decades ago, no one would have thought that “pure” water would become a rare commodity in the future. Today, finding clean and pure water in its natural form is hard. Even the rainwater that falls directly to the earth contains gases, solid particles, and other impurities. The groundwater on the other hand contains minerals and dissolved salts which can be harmful to health. But this water is not our main concern as it can be cleaned using traditional treatment technologies. Our main concern is the water which has been used by man and then discarded. Initially, this water was referred to as “sewage” but now it is called “wastewater”. The direct discharge of wastewater into water bodies without treatment can destroy the aquatic ecosystem of rivers, lakes, ponds, etc.
There is nearly 99.94% water in the wastewater and only 0.06% has suspended solids dissolved. The cloudiness of wastewater is caused by suspended particles, which in untreated wastewater range between 100 and 350 mg/l. Biochemical oxygen demand, sometimes known as BOD5, is a measure of wastewater strength. The BOD5 test determines how much oxygen microorganisms require in five days to break down wastewater. Untreated wastewater has BOD5 levels ranging from 100 to 300 mg/l. Pathogens or disease-causing organisms can be found in wastewater. Coliform bacteria are utilized to identify disease-causing pathogens.
We can classify the wastewater into four major categories:
The wastewater treatment involves a series of steps before discharging it to a water body or reused again. The aim is to reduce or remove organic matter, and suspended solids, recover nutrients, and remove disease-causing organisms, and other pollutants from wastewater.
In the traditional wastewater treatment process, there is a sequential combination of physical, chemical, and biological processes for removal of the impurities and pollutants. Generally, the different degrees of treatment are defined by preliminary, primary, secondary, and tertiary treatment in which the treatment level is increasing in the same order. After going through these treatments, the wastewater is generally disinfected using chlorine and can be reused again. Let’s understand each of these treatments in brief:
The preliminary treatment is the initial step, focusing on the removal of large solid materials that could clog or damage subsequent treatment systems. This includes items such as sticks, rags, food particles, sand, gravel, and even non-biodegradable objects like toys.
Key processes and equipment:
The collected debris is typically sent to a landfill for disposal.
In the primary treatment stage, wastewater is held in sedimentation tanks to allow heavier particles to settle at the bottom, while lighter materials, such as grease and oils, float to the surface and are skimmed off.
Key benefits of primary treatment:
Additionally, some heavy metals, organic nitrogen, and phosphorus attached to the solids are also removed. However, colloidal and dissolved substances remain largely unaffected at this stage.
The secondary treatment focuses on removing dissolved and colloidal organic materials through biological and chemical processes. This stage employs aerobic microorganisms to digest organic pollutants in the presence of oxygen.
Key processes:
Objectives:
Oxygen supply is critical in this stage to sustain microbial activity and optimize the degradation of organic matter.
This refined version ensures a more logical flow, provides additional details for better understanding, and uses consistent formatting for clarity.
While primary and secondary treatment processes effectively remove most of the BOD (Biochemical Oxygen Demand) and suspended solids from wastewater, they often fall short of ensuring sufficient water quality for environmental protection or reuse in industrial and domestic applications. To address these gaps, advanced wastewater treatment methods are implemented to further eliminate organic matter, suspended solids, nutrients, and toxic materials.
Advanced wastewater treatment refers to processes designed to produce higher-quality effluent than what secondary treatment provides. These methods can be categorized into three major types based on their process flow:
Tertiary treatment builds on secondary treatment by introducing additional processes to enhance water quality. This could range from simple filtration systems to more complex setups involving multiple unit processes aimed at removing specific contaminants such as organic matter, suspended solids, nitrogen, and phosphorus.
Key processes in tertiary treatment:
This method combines physical, chemical, and biological processes to achieve desired effluent quality. Unlike tertiary treatment, which adds units after conventional biological processes, physicochemical treatment integrates these processes.
Examples include:
This hybrid approach integrates biological and physical-chemical treatments within a single process stream, optimizing the removal of complex pollutants.
Advanced treatment processes are typically implemented to meet specific goals, including:
Traditional secondary treatment systems can remove 85-95% of influent BOD and suspended solids, producing effluent with average BOD concentrations of around 20 mg/L and COD (Chemical Oxygen Demand) levels of 60-100 mg/L. However, this level of treatment is often insufficient for applications requiring high-quality water. Advanced wastewater treatment is capable of removing contaminants at a micro-level, ensuring water is safe for reuse in industrial processes, cooling systems, or even as an indirect supplement to domestic water supplies.
By implementing advanced methods, wastewater treatment facilities can achieve a higher standard of effluent quality, contributing to sustainable water management and environmental conservation.
Advanced wastewater treatment methods employ a combination of biological and physicochemical processes to enhance the removal of contaminants beyond traditional methods. Below are some popular methods:
The IDAL system is widely used for nitrogen removal in wastewater treatment, particularly in Australia. It involves a two-step biological process:
The system performs biological oxidation and clarification in a single tank, with three distinct operations occurring sequentially:
The BEPR system targets phosphorus removal using specialized bacteria capable of storing polyphosphates. The process works as follows:
Advantages of BEPR:
Deep bed filtration, a well-established method, plays a crucial role in tertiary treatment due to increasingly stringent effluent standards. Popular types include:
Key Consideration: The floc size formed during flocculation must be suitable for filtration.
Improved Approach: Use of a mobile bed filter or a prefilter (e.g., floating media) combined with CFF for continuous sand washing.
In addition to widely used methods, several emerging advanced technologies offer promising solutions for industrial wastewater treatment. Though still in early development, they have significant potential to overcome the limitations of existing systems.
This technology simultaneously treats wastewater, reduces sludge byproducts, and produces biogas. Traditional wastewater systems struggle to manage large volumes of leftover sludge, but thermal hydrolysis treats it as a resource.
After collecting sludge, it is heated and pressurized in large vats (160–165°C and 7–12 bars) to produce biogas.
Types of Thermal Hydrolysis:
An innovative bioelectrochemical technology that uses microorganisms to generate electricity while treating wastewater.
Process:
This dual-purpose method provides clean energy and effective wastewater treatment.
This method uses solar energy to significantly reduce sludge production—up to 80% less than traditional methods. It employs photocatalysts activated by sunlight to break down organic contaminants, minimizing sludge generation.
A fixed-film biological treatment method designed to reduce organic matter and ammonia.
Key Features:
ASBR operates as a “fill-and-draw” system with multiple tanks functioning as batch reactors.
Process:
ASBR improves treatment efficiency and flexibility for small and large-scale applications.
Combines suspended and fixed biomass for more efficient treatment, often used to retrofit existing plants.
How It Works:
Traditional wastewater treatment technologies are effective at removing basic contaminants and suspended solids. However, as industrial processes evolve, the contaminants in wastewater are becoming more complex and toxic. Addressing these advanced contaminants requires cutting-edge treatment technologies.
At Wipro Water, we leverage the latest advanced wastewater treatment solutions to deliver high-quality, clean water. This treated water can be safely reused for industrial applications or other forms of consumption, supporting both environmental sustainability and operational efficiency