OBJECTIVE
For reliable water reuse, organic material has to be removed from the water. Our aim is to develop a stable and robust process for the removal of organic material and its conversion into biogas. By combining and adapting separation and anaerobic conversion technologies, our process can deal with the large fluctuations in wastewater flow rates that are typical to monsoon climates such as New Delhi. This system will ensure superior effluent quality which is suitable for additional treatment.
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In warm climates, wastewater treatment using anaerobic (no oxygen present) biological processes, have the advantage of efficiently reducing the organic material in municipal wastewaters and producing energy in the form of biogas. One promising technology is to integrate membrane filtration with anaerobic treatment in an anaerobic membrane bioreactor (AnMBR).
Energy recovery is an intrinsic part of anaerobic technology. Through biological conversions, the energy contained in organic components is released in the form of raw biogas. This biogas is used as fuel for a solid oxide fuel cell (SOFC) that produces electricity. By using this approach high quality energy is generated which supports the energy demand of this first treatment step.
AnMBRs have a small footprint and can treat concentrated wastewaters making them suitable for urban environments. AnMBRs are known for producing particle free high quality effluent that is suitable for other treatment processes. Despite these advantages, one of the major problems is the relatively large (costly) membrane area required to sustain stable operation. As a consequence AnMBRs typically do not handle large fluctuations in water inflow rates.
Because New Delhi experiences monsoons, high water flows are expected and have to be dealt with. Through exploring and developing additional separation technologies namely dissolved air flotation (DAF), this research project seeks to maintain the superior effluent quality of AnMBRs by dealing with the fluctuation in water inflow rates while remaining cost effective.
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RESEARCH
In the initial research stages, the interaction between different separation, conversion and recovery technologies are investigated. By combining the separation and conversion technology a robust system will be developed. Special attention will be given to optimization of the membrane modules, the effect of the combined technology on the anaerobic process conditions and the direct linkage of biogas utilising fuel cells.
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The removal and conversion of organic material is the important first step in wastewater treatment systems. Organic solids or particulate material could cause unwanted biological activity in other treatment processes and pose severe health risks. Anaerobic membrane bio reactors (AnMBRs) are a proven technology that can produce particle free water and biogas.
The research focus will be on ensuring optimal performance of the membrane filters that are prone to clogging. Methods such as below critical flux operation (i.e. filtrate flux above which irreversible deposits take place), periodic back washing, chemical cleaning and improving surface properties of the membranes will be investigated.
The energy that is contained in the biogas can be recovered using solid oxide fuel cells (SOFC). Biogas typically contains methane (CH4), nitrogen (N2) and carbon dioxide (CO2) along with other pollutants such as hydrogen sulphide (H2S), siloxanes and volatile organic compounds. These compounds can damage part of the SOFC and reduce long term performance. Initial research will focus on testing the SOFC with different biogas compositions and the removal of pollutants in the biogas. Another research focus is on making the biogas suitable for direct injection into the fuel cell.
To be able to cope with fluctuating water flows and solids concentrations, water and (organic) particles, have to be separated. The separation technology, dissolved air flotation (DAF) will be used for this purpose. Since DAF uses air bubbles to separate organic solids from the water, oxygen toxicity might be a problem for the anaerobic (no oxygen) bacteria that live in the anaerobic reactor. For this reason research will focus on the effect of oxygen in anaerobic systems and developing alternative gas carriers such as biogas.
For the development and construction of a suitable pilot scale pre-treatment system several steps are needed. Initially, a small scale installation (up to 100 liters per day) is tested with Barapullah drain water. During this initial period, the main focus is on the interaction between the separation and conversion systems. The information obtained from the small scale installation can be used to develop improved process designs.
Next, the improved process designs from the initial phase are used to scale up to 10.000L per day installations. At this stage a robust and high rate anaerobic process combined with a system that can effectively separate solids and liquid will be built based on membrane filtration and or DAF.
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TECHNOLOGY
The organic material in the water will be removed using anaerobic treatment where anaerobic (no oxygen present) bacteria convert the organic material into biogas. The energy that is contained in the biogas will be recovered using solid oxide fuel cells (SOFC). In the Indian context, the pre-treatment process has to deal with large fluctuations in wastewater flow rates. The two technologies membrane filtration (as part of anaerobic membrane bio reactors, AnMBRs) and dissolved air flotation technology (DAF) will be tested to effectively separate solids from the treated wastewater.
SOCIETAL RELEVANCE
Our pre-treatment technology offers a variety of benefits which ensure its utilization in practice. Besides the production of a particulate-free nutrient-rich irrigation water, several by-products are formed. Recovering these “value-added” products, will make the treatment system very interesting from a broader local resource recovery and economic perspective. By demonstrating such a robust wastewater pre-treatment technology and show the scaling up potential in an urban context, we contribute to the success of future water reclamation projects.
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Safe reuse of effluent
By developing robust systems that ensures reliable first source of water, we contribute to making water reuse possible and applicable in various locations. The anaerobic membrane technology produces organic material free and nutrient rich irrigation water which could be used for farming after the water quality aspects are addressed (project 1B).
Source of income
The recovery of additional “value-added” by products could make the system very interesting in a local resource recovery perspective. The biogas utilization efficiency can be doubled using SOFCs, making the treatment more energy efficient. Also, the sludge (bacterial slurry) produced in the anaerobic treatment can be used locally for the production of activated carbon or in as partial replacement of clay in making bricks and tiles suitable for construction.
Knowledge creation & dissemination
Our goal is to create a robust wastewater pre-treatment system that can be used in an urban context. By actual demonstration of robust wastewater pre-treatment technology in an urban context we contribute to the success of future water reclamation projects.
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FEATURES
The developed technologies will be able to treat water effectively while promising stable performance even with fluctuation in water flows and solids concentrations, thereby ensuring stable operation of the post treatment steps (subproject 3: Vital urban filters and Photobioreactors). Our technology has the following features:
- High rate anaerobic digestion process
- Novel integrated solid/liquid separation solutions
- Resistant to large hydraulic fluctuations
- Hybrid anaerobic digester dissolved gas flotation reactor
- Cost-effective through energy and resource recovery
COLLABORATION & PARTNERS
The project is a collaboration between the Indian and Dutch research institutes. The Indian side is represented by Indian Institute of Technology Delhi and The Energy and Resources Institute. On the Dutch side, Delft University of Technology and IHE Institute for Water Education are involved.
Our contributing partners are:
- Nijhuis Water Technology BV which helps us in developing dissolved air/gas flotation (DAF/DGF) technology by providing equipment and expertise.
- JCI is our membranes supplier and offers us materials and expertise.
- Saxion University of Applied Sciences also focuses on AnMBR technology and provide student exchange and their expertise on cost effective reactor automation.
- WASTE provides their expertise on solid waste management to help us handle the plastics, debris etc. that float through the drains.
All our partners can be found here.
