The project had three main objectives:
to develop and field-test innovative FILTER techniques for sustainable irrigation with wastewater at a demonstration site in Shanxi Province;
to promote the application of FILTER technology for sustainable irrigation with wastewater in Shanxi and other Chinese provinces;
to develop simple integrated approaches for siting, design and operation of FILTER and related technology in China and Australia.
Two thirds of China’s total crop production is from irrigated lands. There is, however, increasing pressure on water supplies from the spread of urbanisation and industrialisation. There is also increasing production of wastewater, resulting in environmental pollution. Most rivers, lakes, bays and groundwater sources are showing increasing signs of severe pollution, including from organic matter, nutrients, heavy metals and other toxic chemicals. As a result water use in agriculture, fisheries and recreation is greatly limited. Reusing effluent in suitable agricultural conditions is a possibility, provided appropriate land treatment and reuse techniques are in place. Soils with impeded drainage are particularly vulnerable to degradation and pollution unless properly managed.
The Australian Filtration and Irrigated cropping for Land Treatment and Effluent Reuse (FILTER) technique was developed for using effluent on soils with impeded drainage. FILTER uses nutrient-rich effluent for intensive annual cropping in combination with filtration of excess effluent through the soil to a sub-surface drainage system during periods of low-intensity cropping and high rainfall. A past ACIAR project proved the potential of the FILTER technique in China and Australia for sustainable irrigated cropping and nutrient reuse. This project promoted the use of FILTER in Shanxi Province.
Objective 1. Develop and field test innovative FILTER techniques for sustainable irrigation with wastewater at a demonstration site in Shanxi Province
1.1 Planning meeting at Shanxi
Prior to the Australian team visiting Shanxi extensive preparatory work was undertaken to facilitate progress at the planning-meeting and to assist in the experimental trial installation at the field site. This involved making detailed planning of the field experiments in Email consultation with the Shanxi researchers, which is described in detail in Appendix A. The Australian team members also purchased and lab tested the field equipment subsequently used for automatic monitoring of the soil physical properties of the Shanxi, Datong site. The testing was done at the CSIRO Brisbane laboratory. The equipment was then taken as hand luggage by the Australian research team visiting the Shanxi site. The Australian research team consisted of John Blackwell, Nihal Jayawardane, Freeman Cook and Shahbaz Khan. They were joined by IWHR researchers Gao Zhanyi and Cheng Xianjun on the visit to the Datong field site. Prof. Yang from Wuhan University also joined the field trip.
1.2 Install irrigation system at the field site and establish crops
As foreshadowed in the initial planning documents, the Australian team expected that the field site would be prepared and crops established prior to the visit to Shanxi. However the Shanxi researchers were unable to secure the proposed research site through negotiations with the land owners. This was a major setback to carrying out the studies as originally planned, as the planned experimentation for the first cropping season had to fit into the tight window of opportunity for cropping, under the very harsh weather conditions at Shanxi. Shanxi Province experiences long and very cold winter periods, resulting in a short summer cropping period. An adequately prepared field site was essential to impose the heavy hydraulic loading of the wastewater in FILTER systems.
The first day of the Shanxi visit were spent in looking at alternative field sites and making associated changes in planning of the field trials. These are described in detail in the report on the field visit to Shanxi site, presented in Appendix B. The alternate site chosen consisted of an established farmer’s maize field. Due to the short cropping season, it was also decided that the farmer will be allowed to irrigate his established crop with sewage irrigation to supplement the natural rainfall, under the existing land preparation conditions. The focus of the research studies in the first cropping season was to evaluate the soil physical properties at the experimental site, which will facilitate designing of the appropriate horizontal or vertical drainage system to allow adoption of the modified FILTER technology at the site, in the following seasons.
1.3 Install instrumentation
A modified plan of the instrumentation for automatic measurement of the soil physical properties was developed and the field instruments were installed, as described in detail in Appendix C. Soil pits were dug in the centre of each of the three plots to be used in the field trial. Instruments to measure soil matric potential, soil moisture content and temperature were installed at different depths in each plot. The cables from these instruments lead to a junction box which is connected to a data logger powered by a solar panel. Subsequently, an automatic weather station was also connected to the data logger.
1.4 Characterise soil hydraulic and hydrological properties
From each plot undisturbed soil cores were collected at different soil depths for the characterisation of soil physical and chemical properties.
The automatic data collection on soil moisture content and matric potential at the trial site is described (Appendix C) and the data analysed to derive the soil physical properties.
In addition, a separate infiltration experiment was conducted by Evan Christen during a visit to the field site in August 2004 which is described in a travel report (Appendix D). The detailed hydraulic analysis of the data from this infiltration experiment is described in Appendix E.
1.5 Apply irrigation on a preliminary schedule
Due to the trial being installed on a farmers field with an established maize crop, irrigation could only be potentially applied at a low rate when required to supplement rainfall. However, due to receipt of plenty of rainfall during the summer cropping season, supplementary irrigation was not required to be applied. After carrying out land preparation for the following winter season and subsequent summer cropping seasons, a higher hydraulic loading will be used. This will allow an evaluation of the efficacy of maintaining high hydraulic flows and pollutant removal at the site.
1.6 Monitor hydrology, crop performance and pollutant removal
Details of the preliminary hydrological studies conducted at the site are provided in Appendix F.
1.7 Monitor cold weather infiltration performance
A visit was undertaken in November 2004 by the Australian research team of John Blackwell, Freeman Cook and Tapas Biswas to Shanxi to initiate monitoring of different management options for enhancing cold weather wastewater infiltration (Appendix G). Prior to the visit, discussions were held with the Shanxi researchers on preparing the site for wastewater ponding on a flattened soil surface, with high bunds around each of the plots. A report on the performance of the plots during cold weather infiltration is provided in Appendix G
1.8 Develop drainage design
The analysis of the data on the soil physical properties at the field site and on-field observations indicates that the soils at the site have high hydraulic permeability and deep watertables. The site therefore appears to be more suitable for a modified FILTER system with a vertical drainage system.
On the basis of hydrogeological properties at the experimental site, a radial flow model of a FILTER site is being developed to test recharge, pumping and drawdown scenarios.
1.9 Develop annual irrigation/drainage schedule and practices
A visit was undertaken by the Australian research team of John Blackwell, Shahbaz Khan, Tapas Biswas and Roy Zandona in May 2005 to evaluate the progress of the field studies and plan a summer filtration season with high wastewater loading. Discussion and field studies were conducted with the Shanxi researchers to develop plans and field protocols to monitor water flow and pollutant removal during summer filtration.
Objective 2. Promote the application of FILTER and other technology for sustainable irrigation with wastewater in Shanxi and other Chinese provinces
2.1 Visit potential sites
Appendix H provides an account of the work carried out by IWHR staff in visiting potential sites for adopting new approaches to wastewater renovation and discussions with the wastewater managers on the potential application of FILTER technology with suitable modifications. A dialogue has been developed with wastewater managers in Lake Dianchi in Kumung-Yunnan Province, Beijing Water Commission and central government authorities attached to MOST.
2.2 Assist wastewater managers with plans to apply new technology
IWHR researchers have developed a novel approach to modifying FILTER systems for application in the cold winter areas in northern China, by combining FILTER with existing polyhouses providing around-the-year crop production for urban centres in northern China. A preliminary trial site has been established in the Beijing Water Commission area to develop and test the efficacy and potential application of the combined technologies.
Objective 3. Develop simple integrated approaches for siting, design and operation of FILTER and related technology in China and Australia
Activities associated with this objective are only planned for year 2 of the project.
Objective 1 At Yanggao County near Datong city in Shanxi province, a field site consisting of three plots was installed on a farmer’s field to evaluate the catchment-FILTER technology. The scientists studied summer, winter and groundwater components, using instrumentation to monitor wastewater and pollutant flows through the soil. During the summer season a very high hydraulic loading rate of domestic wastewater, around three times the crop’s water requirement, was applied to a maize crop established on the FILTER plots. The pollutant removal in the process of wastewater movement through the soil and beyond the crop rooting depth was monitored. Concentrations of the major pollutants in the wastewater - Total P, Total N, NH4-N, Organic-N, and COD concentrations - were markedly reduced (by 97, 77, 99, 50 and 75% respectively) in the drainage water flows beyond the root zone.
These pollution removal rates in the Catchment-FILTER system are similar to those previously observed in land-FILTER sites with high watertables in Australia and China. However, due to better soil aeration conditions at this Catchment-FILTER site with deep watertables, the concentration of NO3-N levels in drainage water increased from zero to around 9 mg per litre, which needs close monitoring in future studies on field adoption of Catchment-FILTER technology. In spite of the high hydraulic loading rates of wastewater, the maize crop yields of 9.6 t per ha in FILTER plots compared well with district yields of 10.7 t per ha.
During the first winter season, shallow-ponding systems for wastewater infiltration used in north America under freezing conditions were tested at the Yanggao field site, but failed due to the heavy frosts in Datong. During the second winter season, an alternative deep-ponding approach was successful in maintaining an infiltration rate of around 0.2 m per day, with the formation of a 0.3 m floating ice-cap at the wastewater surface.
Soil-water-crop-solute models were applied for predicting wastewater and solute movement through the soil during the summer cropping season. In the second cropping season, the model provided accurate predictions of wastewater and solute flows through the soil profile. Application of the MAIZEMAN model provided accurate estimates of crop biomass accumulation, crop duration, soil water movement and nitrogen leaching.
The potential hydrogeologic impacts of the proposed FILTER system on the surrounding area were investigated. Data available from an existing long-term pond experiment were used to characterise aquifer properties. Boundary flux analysis carried out to quantify the net impact of FILTER on the surrounding areas indicated that a well designed and managed vertical drainage system could be used in a catchment-FILTER approach for domestic wastewater renovation at the site. There is a need to combine the hydrology modelling with detailed monitoring of biological and chemical contaminants present in the wastewaters, under the management practices proposed and adopted for the Catchment-FILTER site to ensure long-term sustainability.
Objective 2 Promotion of the application of FILTER technology for sustainable irrigation with wastewater irrigation in Shanxi and other Chinese provinces was carried out by the IWHR and SIWR researchers. The IWHR researchers in collaboration with Beijing Water Resources Bureau developed and successfully field-tested an innovative FILTER-polyhouse system to combine the FILTER technology with greenhouse agriculture systems to overcome the low infiltration during winter freezing conditions in north China. They also field-evaluated a modified land-FILTER system for treating domestic wastewater, in collaboration with Yunnan Environment Research Institute. The FILTER technology was also promoted at discussions with the Ministry of Science and Technology (MOST) and provincial authorities.
Objective 3 Simplified integrated approaches for siting, design and operation of the new FILTER and related technology in China and Australia were developed. These approaches are incorporated into the guidelines for using Land-FILTER and Catchment-FILTER systems for using wastewater in China and Australia.