Faecal Sludge Treatment Plants (FSTP)
Treatment Philosophy
The proposed treatment philosophy for the Faecal Sludge Treatment Plant (FSTP) is based on a comprehensive approach integrating various advanced technologies to treat faecal sludge efficiently and sustainably and septage. The primary aim is to transform the incoming sewage into harmless forms for the environment, ensuring compliance with environmental standards while maximizing resource recovery.
Preliminary Treatment
The treatment process begins with preliminary treatment, which involves the removal of coarse solids and large materials from the sewage. Inlet channel & scum removal system are utilized to trap large objects and municipal waste, preventing clogging and pump failures and enhance the efficiency of subsequent treatment processes.
- Bar Screens: Bar screens are installed at the influent of the treatment plant to trap large objects and municipal waste. These screens act as a physical barrier, preventing coarse solids from entering the treatment system. They are typically positioned vertically or inclined to efficiently capture debris while allowing liquid and smaller particles to flow through.
- Grit Removal: Grit removal is essential to protect mechanical equipment and enhance the efficiency of subsequent treatment processes. It involves the separation of heavier particles such as sand, gravel, and grit from the sewage. This process reduces abrasion and wear on pumps and other components.
Primary Treatment
Primary treatment is a crucial stage in the wastewater treatment process, focusing on the physical settling or filtration of large solids and the removal of settleable organic and inorganic solids through bio-digestion processes. This document provides an overview of the primary treatment processes employed in wastewater treatment plants, including anaerobic digestion, denitrification, and chemical dosing for the reduction of total suspended solids (TSS) and other pollutants.
- Anaerobic Digestion: Following preliminary treatment, wastewater enters the primary treatment stage where anaerobic bacteria decompose organic matter. This process generates biogas and produces a partially stabilized by-product known as DigeCity. Anaerobic digestion significantly reduces organic pollutants and pathogenic bacteria present in the wastewater.
- Denitrification: After anaerobic digestion, the wastewater undergoes denitrification in an anoxic tank. Denitrification is the process of removing nitrogen compounds from the wastewater by facilitating the conversion of nitrate to nitrogen gas. This helps in reducing nitrogen levels in the treated water, preventing environmental damage such as eutrophication.
- Primary Settling Tank: Once denitrification is complete, the wastewater is collected in a collection sump before being fed into the primary settling tank. The primary settling tank is equipped with a flash mixer and chemical dosing system. These systems are used to reduce the concentration of total suspended solids (TSS) and other polluting parameters in the wastewater.
- Flash Mixer: The flash mixer is a mechanical device used to rapidly disperse chemicals into the wastewater. It ensures efficient mixing of chemicals, such as coagulants or flocculants, with the wastewater to facilitate the formation of flocs. These flocs entrap suspended solids, making them easier to remove during settling.
- Chemical Dosing System: The chemical dosing system is responsible for accurately dosing chemicals into the wastewater to achieve the desired treatment objectives. Common chemicals used in primary treatment include coagulants, such as ferric chloride or aluminumsulfate, and flocculants, such as polymers. These chemicals aid in the aggregation of suspended solids, improving their removal efficiency.
Secondary Treatment
Secondary treatment further treats the sewage from primary treatment to remove residual organics and suspended solids. Advanced technologies such as Inclined Plate Settlers / tube settler and Moving Bed Biofilm Bioreactors (MBBR) are employed for fine filtration and biological treatment. Aerobic microorganisms metabolize remaining organic matter, producing inorganic end-products and further enhancing effluent quality.
- Tube settler: Tube settlerare utilized for fine filtration and separation of smaller solids and particles remaining in the sewage. They offer a large effective settling area, improving the efficiency of clarification processes. Tube settler can be integrated into existing treatment systems to increase flow rates and reduce the footprint of clarifiers.
Moving Bed Biofilm Bioreactors (MBBR): MBBR combines suspended growth and attached growth processes for effective biological treatment. It utilizes simple floating media as carriers for attached growth of biofilms. MBBR units are designed based on wastewater characteristics and local conditions, offering high removal efficiencies for BOD, nitrogen, and phosphorus.
Moving Bed Biofilm Bioreactors (MBBR) in Wastewater Treatment
Moving Bed Biofilm Bioreactors (MBBR) represent an innovative and effective approach to biological treatment in wastewater treatment plants. MBBR systems integrate both suspended growth and attached growth processes, utilizing floating media as carriers for the development of biofilms. These biofilms host a diverse community of microorganisms responsible for the degradation of organic matter and the removal of nitrogen and phosphorus from the wastewater.
Key Components of MBBR
Floating Media: MBBR units consist of plastic media with a high surface area-to-volume ratio. These media pieces are typically small in size and designed to remain buoyant in the wastewater, providing ample surface area for the attachment and growth of microbial biofilms.
Aeration System: Aeration is essential in MBBR systems to provide oxygen to both suspended and attached microorganisms. Aerobic conditions are maintained to facilitate the biological processes responsible for organic matter degradation and nutrient removal.
Mixing Mechanism: Proper mixing within the MBBR tank ensures uniform distribution of wastewater and media, promoting contact between the microbial biofilms and the organic compounds present in the wastewater. This enhances treatment efficiency by maximizing the utilization of available surface area for microbial activity.
Moving Bed Biofilm Bioreactors (MBBR) represent an innovative and effective approach to biological treatment in wastewater treatment plants. MBBR systems integrate both suspended growth and attached growth processes, utilizing floating media as carriers for the development of biofilms. These biofilms host a diverse community of microorganisms responsible for the degradation of organic matter and the removal of nitrogen and phosphorus from the wastewater.
Operation of MBBR
Attached Growth Process: Microorganisms attach themselves to the surface of the floating media within the MBBR unit, forming biofilms. These biofilms serve as active sites for microbial activity, where organic matter is metabolized and nutrients are removed through biological processes.
Suspended Growth Process: In addition to the attached growth process, suspended microorganisms present in the wastewater contribute to biological treatment within the MBBR system. These microorganisms utilize the organic compounds in the wastewater as a carbon source, further enhancing treatment efficiency.
Advantages of MBBR
High Treatment Efficiency: MBBR systems offer high removal efficiencies for biochemical oxygen demand (BOD), nitrogen compounds (ammonia, nitrite, and nitrate), and phosphorus, making them suitable for treating a wide range of wastewater types.
Flexibility and Adaptability: MBBR units can be customized and designed based on the specific characteristics of the wastewater and local environmental conditions. This flexibility allows for the optimization of treatment performance and ensures effective nutrient removal.
Compact Footprint: Compared to conventional biological treatment systems, MBBR units have a smaller footprint, making them suitable for applications where space is limited.
In conclusion, Moving Bed Biofilm Bioreactors (MBBR) offer a versatile and efficient solution for biological treatment in wastewater treatment plants. By combining suspended and attached growth processes, MBBR systems effectively remove organic matter, nitrogen, and phosphorus from wastewater, contributing to the production of high-quality effluent for discharge into the environment.
Tertiary and Advanced Treatment
Tertiary treatment involves advanced processes for the removal of remaining contaminants and pathogens. Effluent undergoes filtration through multi-grade filters for the removal of particulate matter, followed by treatment with activated carbon filters to eliminate trace organics and pollutants. Backwash systems ensure the continuous regeneration of filter media, maintaining treatment efficiency. The tertiary system also consists of ozone based disinfection system ,Ozonator, also known as an ozone generator, plays a crucial role as a tertiary treatment system in wastewater treatment plants. It employs ozone, a powerful oxidizing agent, to effectively remove pollutants and contaminants from wastewater, ensuring high-quality effluent before discharge.
- Multi-Grade Filters: Multi-grade filters consist of multiple layers of coarse and fine sand for the removal of particulate matter from the effluent. They work at higher specific flow rates and have high dirt-holding capacity, making them suitable for pre-treatment of ion exchange and membrane systems.
- Activated Carbon Filters: Activated carbon filters are utilized for the removal of trace organics and pollutants from the effluent. Activated carbon has high surface area and adsorption capacity, making it effective for removing contaminants such as chlorine, color, and organic compounds.
- Ozonator serves as a highly effective tertiary treatment system in wastewater treatment plants, offering efficient pollutant removal, odor control, and environmental sustainability. Its ability to generate ozone and oxidize a wide range of contaminants makes it a valuable asset in ensuring the production of high-quality treated effluent.
- Ozone Generation: Ozonators utilize either ultraviolet radiation or an electric discharge field to convert oxygen (O2) molecules into ozone (O3) molecules.
- Oxidation: Ozone is a highly reactive gas that readily reacts with various pollutants, including bacteria, molds, organic compounds, and inorganic substances such as iron and sulfur. This oxidation process breaks down pollutants into simpler, less harmful compounds.
- Pollutant Removal: Ozone effectively kills bacteria and inactivates pathogens present in wastewater. Additionally, it oxidizes substances like iron and sulfur, facilitating their removal through subsequent filtration processes.
- Odor Control: One of the notable benefits of ozone treatment is its ability to eliminate foul odors associated with wastewater. Ozone reacts with odorous compounds, neutralizing them and leaving behind odor-free effluent.
- Residue-Free: Unlike some chemical treatment methods, ozone treatment does not leave behind any harmful residues or by-products. Once ozone reacts with pollutants, it converts back into oxygen (O2) molecules, leaving no trace in the treated water.
- Advantages:
- Efficient Bacteria Elimination: Ozone effectively kills bacteria, viruses, and other pathogens present in wastewater, ensuring the safety of the treated effluent.
- Versatile Oxidation: Ozone’s strong oxidative properties allow it to oxidize a wide range of pollutants, including organic and inorganic compounds, improving overall water quality.
- Odor Elimination: By neutralizing odorous compounds, ozone treatment helps in controlling unpleasant odors emanating from wastewater treatment facilities.
- Minimal Residue: Ozone treatment does not produce harmful residues or by-products, making it environmentally friendly and safe for discharge.
- Rapid Decomposition: Ozone quickly decomposes back into oxygen molecules after treatment, minimizing environmental impact and ensuring compliance with regulatory standards.
Environmental Sustainability
Throughout the treatment process, environmental sustainability is prioritized by minimizing energy consumption, reducing chemical usage, and ensuring compliance with regulatory standards. Technologies selected are ecologically viable, replicable, and adaptable to diverse climatic conditions, ensuring long-term environmental stewardship.Overall, the treatment philosophy emphasizes a holistic approach towards faecal sludge management, integrating innovative technologies for effective treatment, resource recovery, and environmental protection.