MLS 1.3: Sewage
Practice and options for better phosphorus recycling in the Changping or Xiaojiahe sewage plant.
The Mutual Learning Sessions (MLS) compliment the guiding theme of the conference (“learning from cases – exploring policy options) by encouraging participants to focus on specific, real-world cases and gain a greater understanding of the context and complexities of each case. The aim is to understand the mechanisms, options and barriers of successful sustainable transitions at an individual case, and then extract generic conclusions that can be applied to other, similar cases or general strategies.
MLS 1.3 will consider the practice and options for phosphorus recovery at a Chinese sewage treatment plant. Sewage treatment plants receive considerable amounts of P from human and industrial wastes, and in order to close the loop on P flows, this must be recovered and recycled. The Chinese sewage treatment plant studied in MLS 1.3 serves as an excellent case for recovering P from sewage, as it receives huge amounts of P from the wastes of a mega city and is situated within a country with high P demand for agriculture. Participants will gain a greater understanding of the sewage plant itself by studying an information booklet that will be provided before the conference. This will include information about the existing operational and regulatory conditions, as well as societal or cultural aspects associated with recycling P from sewage. Participants will further increase their understanding of the specific case during the conference by visiting the sewage treatment plant and discussing the case with practitioners. The state-of-the-art technological options for phosphorus recovery at various stages throughout the treatment process will be assessed in the context of this specific sewage plant, including the direct application of sewage sludge to agricultural land and the potential options for recovery of struvite or HAP from the liquid phase, sewage sludge and incineration ashes. This will lead to an identification of the opportunities (what is possible?) and the barriers (what is hampered?) for implementing such recovery technologies, and the development of potential solutions (how can the “impossible” become possible?) for increased P recovery. The aim is that the lessons learned from this process will have generic aspects that can be applied to other sewage plants, and will be useful in the development of general strategies for recycling P from sewage.
Umbrella Team Representative: Dr. Christian Kabbe, Berlin Center of Competence for Water.
Case Scientist /Science Lead: Yanming Li, China Agriculture University, Beijing.
Case Agent / Practice Lead: Tao Zhang, China Agriculture University, Beijing.
Support Team: James Cooper, University of Birmingham, UK.
* This is the first version of the description of what will be dealt with in the MLS 1.3 Sewage. A group of practitioners and scientists are currently revising this abstract and composing a booklet which will prepare all participants for the MLS on June 18. If you want to join, please contact James Cooper (firstname.lastname@example.org), member of the TD Support Team for MLS 1.3, or Anh Pallas (email@example.com), Science Manager of Global TraPs.
Executive Summary of MLS 2.1 Sewage of the 1st Global TraPs World Conference, Beijing 2013 (written 8/2013; released 3/2014)
Preliminary note: The following text comprises the orientations discussed and identified in Mutual Learning 1.3. James Cooper (PhD student University of Birmingham, U.K.), facilitated this Mutual Learning Session of the 1st Global TraPs World Conference, July 18-20, 2013 and is responsible author of this summary. 5 people participated in this joint session . For further questions, please contact Prof. Ulli Vilsmaier, Leuphana University, Lüneburg (firstname.lastname@example.org) or Christian Kabbe (email@example.com).
The aim of MLS 1.3 – Sewage was to consider the practice and options for phosphorus recovery at a Chinese sewage treatment plant. This was fulfilled on the 18th June 2013 by visiting the LuNan WWTP, gathering information about the works from plant operatives, and discussing the options for increased P recovery during a meeting which followed the site-visit. The discussions focussed on identifying the opportunities (what is possible?) and the barriers (what is hampered?) for implementing P-recovery technologies, and discussing potential solutions (how can the “impossible” become possible?). A number of useful policy orientations were also proposed during the sessions.
The LuNan WWTP, situated in South-West Beijing, serves a population of 360,000 people, receiving 80,000 tonnes sewage per day with a total P concentration around 6.3 mg/l. The plant is designed with biological phosphorus removal systems and back-up iron dosing to achieve effluent concentrations of 0.8 mg P/l, although actual effluent concentrations average 0.3 mg P/l. Iron dosing is required during the winter to compensate for poor bio-P removal, and during 2012 the bio-P removal process was put on hold while sludge bunking problems are overcome. The plant produces around 100 tonnes of sludge each day, which is transported off site to a factory and turned into compost.
The use of iron dosing for P-removal acts as a barrier for many P-recovery technologies. In order to increase P recovery, the issues with the bio-P system would have to be overcome, including making the process independent to the weather so that iron dosing is not required during the colder months. A method of releasing phosphorus into solution would be required for P-recovery. Anaerobic digestion of sludge would allow subsequent recovery of P, as struvite for example, and would also enable energy to be recovered from the sludge. However, this may involve large investments.
The following policy orientations were developed during the discussions:
- Increase global sanitation to prevent pollution and disease, and enable recovery and recycling of resources from sewage.
- A requirement, or targets, for P recovery from waste streams according to state-or-the-art options.
- Establish an independent, multi-stakeholder working group to produce and frequently update state-of-the-art documents for P recovery and recycling.
- End users (including fertilizer industry, farmers etc.) to produce a definition (catalogue) of their requirements of recycled P products.
- Greater support for piloting and demonstration of novel technologies, including financial support and increased flexibility of emissions standards during trial periods.