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DDHS Wastewater Treatment

Denitrifying Downflow Hanging Sponge System for Decentralised Wastewater Treatment

We have developed a biological wastewater treatment system to treat domestic wastewater in a cost effective and energy efficient manner.


With increased development and urbanisation in areas such as Southeast Asia, India and China, a huge gap exists between wastewater generation and treatment infrastructure. Specifically,  almost 80% of the world has little or no wastewater collection infrastructure and less than 40% of wastewater generated in Indian cities is treated1, leading to seriously polluted water courses and an increased threat to public and environmental health. Due to the lack of infrastructure (the most costly part of wastewater management networks), wastewater treatment technologies that require community collection and centralised treatment systems are economically unfeasible.

There is an urgent need for low cost, decentralised wastewater treatment options that can achieve treatment quality similar to centralised systems, but also are easy to manufacture, install and maintain. Therefore, in areas with minimal wastewater management capacity, small-scale and affordable configurations are crucial to encourage treatment at community scale, improving water quality which is especially important where there is direct amenity.

Technology Overview

We have developed a Denitrifying Downflow Hanging Sponge (DDHS) biological wastewater treatment system to treat domestic wastewater in a cost effective and energy efficient manner. The technology exploits a layered three-dimensional structure of reticulated sponge as a support media for microbial communities to treat the waste. This structure creates alternating redox conditions and results in a high level of treatment performance and stability with minimal energy investment than conventional technologies.

The DDHS system is effective at removing organic matter, secondary nutrients (especially nitrogen), bacteriological pathogens and genetic pollutants, namely antibiotic resistant genes. Performance has been proven and optimised at laboratory scale and the system has been demonstrated at pilot scale (population equivalent 12) in Johor Bahru, Malaysia.

Relying on passive aeration for the first treatment step that primarily removes carbon means that the DDHS system is energy efficient and cost effective to run. The second step is anoxic, which requires no oxygen. Depending on local topography, whether the system is designed as a single column or two parallel modules, and effluent quality requirements, pumping may be necessary. This energy usage is minimal and could be met using on-site renewable energy sources, e.g. solar PV.


  • >80% COD removal2
  • >90% NH4 and up to 70% TN removal2
  • >90% antimicrobial resistant gene removal3
  • Modular design can be tailored for local needs and environmental pressures
    • Makes system highly scalable
  • Ideal for rural and sub-urban areas where connection to centralised sewer networks may not be feasible and where environmental and public health risks may be greatest
  • Low energy usage (suitable for areas where consistent energy supply is problematic)

IP Status

  • Patent application filed


Dr Luke Judd, Science, Agriculture & Engineering Enterprise Team, Research and Enterprise Services, Devonshire Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK

Pilot scale DDHS wastewater treatment system in Johor Bahru, Malaysia.
Pilot scale DDHS wastewater treatment system in Johor Bahru, Malaysia.


  1. Lamba, M., Gupta, S., Shukla, R., Graham, D.W., Sreekrishnan, T.R., Ahammad, S.Z. 2018. Carbapenem resistance exposures via wastewaters across New Delhi. Environment International, 119, 302-308
  2. Bundy, C.A., Wu, D., Jong, M.-C., Edwards, S.R., Ahammad, Z.S., Graham, D.W., 2017. Enhanced denitrification in downflow hanging sponge reactors for decentralised domestic wastewater treatment. Bioresource Technology. 226, 1–8.
  3. Jong, M.-C., Su, J.-Q., Bunce, J.T., Harwood, C.R., Snape, J.R., Zhu, Y.-G., Graham, D.W., 2018. Co-optimization of sponge-core bioreactors for removing total nitrogen and antibiotic resistance genes from domestic wastewater. Science of the Total Environment. 634, 1417-1423.