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Content archived on 2024-06-18

Performance and validation of HIGH-rate constructed WETlands

Final Report Summary - HIGHWET (Performance and validation of HIGH-rate constructed WETlands)

Executive Summary:
Even though the Water Framework Directive 2000/60/EC, concerning urban WW treatment, forces to treat sewage, there are a lot of small and medium size towns without this service. In addition, many of them cannot deal with energy and maintenance costs of conventional treatment plants making them unsustainable and uneconomic. This is the strong point of extensive technologies like constructed wetlands (CWs). In an economic crisis context, small populations, farms and small F&B industries, must study long-term costs, so it could be an opportunity for low cost technologies like CWs
The HIGHWET project (Grant Agreement Nº: 605445) aimed to perform and validate new approaches of Horizontal and Vertical Constructed Wetlands (HCW and VCW) including innovative materials as gravel bed and aeration devices for increasing biological development by implementing hybrid configurations (anaerobic - CW systems) for decreasing required surface of conventional horizontal CWs.
Three European lead-user SMEs collaborated with two RTD performers to obtain new wastewater (WW) plant configurations based on anaerobic digestion and CW in order to exploit new markets: small towns, industrial Food and Beverage (F&B) and agriculture (livestock farms) sectors. Currently, the towns and companies of these sectors have inefficient and expensive WW treatment systems. In this way, HIGHWET project had a food sector large enterprise as end-user to validate the performance of this new technology and regional water agencies and local government as stakeholders interested in definition of HIGHWET systems and final results.

Project Context and Objectives:
The HIGHWET project aims to perform and validate new approaches of vertical and horizontal constructed wetlands (CWs) including innovative materials as gravel bed and aeration devices for increasing biological development by implementing hybrid configurations (anaerobic - CW systems) for decreasing required surface of conventional horizontal CWs. The outcomes of the project have been the performance of holistic HIGHWET systems capable of operating at high loading rates treating municipal and industrial wastewater (WW). Furthermore, new operation strategies were carried out in order to avoid the gravel bed clogging and extend the lifetime of the systems.
Two configurations have been validated in HIGHWET project. The first configuration consisted of a hybrid hydrolytic anaerobic digester (HUSB) and horizontal CW (HCW) system for raw municipal WW treatment, while second configuration consisted of a combination of HUSB reactor, vertical CW (VCW) and aerated HCW for treatment of high load organic industrial WW. These HIGHWET systems contained an effluent recirculation, air distribution systems and specific natural material in order to configure high rate technologies capable of being clear competitive treatment alternatives to high rate aerobic technologies (Membrane Bioreactor or Extended Aeration reactor) with operation and maintenance (O&M) complex and expensive.
The project objectives as included in GA-Annex I are as follows:
O1. Design, implementation and validation AD-HCW for urban WW. (Related with WP1, 2, 3, 4 and D1.1 and WP2 and 3 deliverables). Achieved in Month 14.
O2. Design, implementation and validation AD-VCW-HCW for industrial WW. (Related with WP1, 2, 3, 4 and D1.1 and WP2 and 3 deliverables). Achieved in Month 14.
O3. Development of an innovative air distribution system. (Related with WP2, 4 and D2.3). Achieved in Month 11.
O4. Implementation of natural waste material/aggregate as gravel bed. (Related with WP2, 5 and D2.3). Achieved in Month 11.
O5. Operation strategy of the HIGHWET systems. (Related with WP4 and WP4 Deliverables). Achieved in Month 24.
Societal-economic targets (Related with WP1, 5 and D1.2 D5.2 and D5.3). Achieved in Month 24.
Environmental impacts (Related with WP4 and D1.2 and D4.3). Achieved in Month 24.
Some delays of first objectives were due to some inconveniences regarding pilot plants implementation during WP2 but this delay was recovered during the 2nd period of the project achieving a 100% accomplishment of all proposed objectives at the end of the project (Month 24).
In GA-Annex I, the objectives are directly related with most of project deliverables, which allows assessing and measuring the accomplishment of objectives and evaluate the project status during its performance.

Project Results:
The work plan followed in HIGHWET project is structured into six work packages (WP) divided into different tasks, each one having a distinctive role towards the accomplishment of the project objectives.
The main research activities have been focused on defining, designing, implementing and validating the two HIGHWET pilot plants to be developed in the project for treating municipal and industrial wastewater. In this sense, the field scale plant configurations of anaerobic digestion and horizontal and vertical flow constructed wetlands systems have been specified, designed, constructed, implemented and validated. The two types of configurations validated during the project were the following:
1. 1st Configuration pilot plant: Anaerobic hydrolytic (HUSB) reactor + HCW systems
2. 2nd Configuration pilot plant: HUSB reactor + two stage CW systems (VCW+HCW)
The global contribution of HIGHWET project to improve the knowledge or technological process of CWs as WW treatment alternative was to develop holistic configurations combining hydrolytic anaerobic digester (HUSB) and vertical and horizontal CWs capable of operating at high loading rate of about 20-50 g BOD/m2d (for the overall system and according the configuration), thus reducing the land requirements by a factor of 2 to 4 regarding conventional CWs. The overall configurations and their components maintain the simplicity of construction and operation of classical anaerobic digesters, HCW and VCW units, but increasing the overall performance of the system through limited artificial aeration and optionally through effluent recycling. The behaviour of the configurations in relation to solids accumulation and energy consumption was also investigated in order to determine its lifetime and general sustainability. In WP2, design, construction or adaptation of hydrolytic anaerobic technologies and aerated vertical and horizontal flow constructed wetland systems were carried out. The start-up and steady-state operation of systems and the validation of HIGHWET configurations were developed in WP3 and WP4 respectively.
The first HIGHWET configuration consisted of a hybrid hydrolytic anaerobic reactor (HUSB) and HCW and it was focused on the treatment of municipal wastewater. This configuration was implemented and validated by HUMIGAL and AIMEN.
The organic load of the influent (raw municipal wastewater) was at least 300 mgBOD/l, in order to achieve the high organic load in the systems. In case that the targeted concentration was not achieved, some addition of substances with organic load, such as starch, molasses, vinegar and/or urea was added to the influent flow to reach the desired concentration.
The pilot plant, located at UDC premises (University of A Coruña), consisted of a hydrolytic anaerobic system followed by a one-stage HCW system.
The second HIGHWET configuration was designed for high organic industrial or agricultural wastewater treatment. The technology was constructed and validated by KILIAN and AU.
The organic load of the influent (raw industrial wastewater) was at least 5000 mgBOD/l in order to achieve the high organic load in the systems. In case that this concentration was not achieved, some additions like starch solution and/or oil and grease were added to the influent flow.
The validation of the plant was carried out at a maximum organic and hydraulic loading rate of 100 gBOD5/m2d and 500-600 mm/d, respectively. On the other hand, the target effluent characteristics to be achieved in the systems were: 10 mgBOD/L; 10 mgTSS/L; 20 mg N total/L and 10 mg P total/L. KILIAN and AU were responsible of the main operation and research in this pilot plant and RIETLAND contributed in the implementation (installation, adjustment, checking test), starting operation and validation of the aeration systems in the vertical and horizontal CWs.

Potential Impact:
One of the main benefits for HIGHWET SMEs is the opportunity to introduce CWs in new markets, where large companies have not been successful. One potential market is Urban WWTP in small towns (below 10,000 population equivalent - PE). Nowadays, some European countries, (i.e. Belgium, France, Ireland, Italy, Luxembourg, Poland, Portugal and Spain) still need to make substantial efforts to improve their compliance with Directive 91/271/EEC (article 4 and 5). Significant investments in these countries have to continue for the necessary improvements of WW treatment of these agglomerations. Conventional CWs have been used in small villages (100-1,000 PE) as an economical alternative to conventional aerobic treatments. But the required conventional CW land for medium size town sanitation entails economic and social limitations.
Also, HIGHWET systems are designed to treat higher organic load WW requiring less area than conventional CWs. Therefore, HIGHWET configurations are suitable to treat organic industrial WW. Currently, there are about 286,000 companies of Food & Beverage industrial sector in the EU, 99.1% of them being SMEs with 2.9 million employees in total (Food Drink Europe, Data & Trends 2014). Many of these F&B companies could be end-users of HIGHWET solutions since their WW composition is suitable to be treated in HIGHWET systems. Table 5 summarises the potential market for HIGHWET project outcomes.
Regarding high organic load WW, an additional potential market is the wastewater of livestock farms (in case of swine manure, an aerobic pre-treatment is necessary to apply HIGHWET systems). There are more than 12 million livestock farms in Europe (EUROSTAT, 2015). Many of them do not have WW treatment and use their liquid effluents directly as fertilizer on surrounding lands. This has a high environmental impact, especially in large farms (with more than 10 hectares of agricultural area), which represent 19.8% of all farms in the EU (2,425,000 farms). This means a lot of new potential customers that HIGHWET SMEs could access with the technology developed. However, the market penetration will be slower than in the other markets due to livestock farms could be more reluctant to install WW treatments and its market share will be negligible at this stage.
It is obvious that urban and industrial wastewater treatment is important to fulfill the water quality requirements of Water Framework Directive. Moreover, Directive 91/271/EEC concerning urban WW treatment states than every town of 2,000-10,000 PE and F&B companies with WW flows higher to 4,000 PE must set up collection and treatment systems. Also, some F&B companies are affected by Directive 2010/75/EU on industrial emissions (integrated pollution prevention and control –IPPC-). Difficulties to comply this legislation are reported due to current infrastructure cannot always achieve Directive quality standards (i.e. Belgium, Ireland, Italy and Portugal).
The main advantage of a HIGHWET European approach is that the system is able to provide a solution for F&B industry and small town WW treatment in different location across EU. This is possible due to similarities in WW characteristics and legislation in EU.
Technologies such as applied in conventional WWTP are not the best solution for small towns and F&B SMEs, due to its high investment and maintenance cost. Therefore, HIGHWET project results are a potential solution in these cases. HIGHWET systems are low cost and easy to operate and maintain.

Main dissemination activities:
- Project website.
- A Short project video of HIGHWET project.
- Poster prepared for diffusion of the objectives of the HIGHWET project.
- Flyers printed to disseminate the main features of the HIGHWET project.
- Letter of invitation to HIGHWET Public seminar and stakeholder meetings.

List of Websites: