Annual Conference 2017 - programme & speakers, 28th September
The following conference sessions and speakers are confirmed for the CWA Annual Conference on 28th September 2017. The full agenda and running order will be published shortly.
The future of rural wastewater treatment works
Prof Bruce Jefferson, Professor in Water Engineering, Cranfield University
Discussion around how the future of rural wastewater treatment works is reimaging the role of the works beyond merely protecting the environment to one that additionally provides valued services to the local community. This goes beyond water and resources (nutrient and heat) to embrace environmental and societal values through wildlife habitat and recreational landscapes.
Constructed wetlands lie at the heart of delivering such a paradigm although the make up and design will need to be adjusted to ensure the value propositions are realised.
The presentation will outline current activities in this space and raise discussion of the future of treatment wetlands.
Community engagement
Revd David Walker, Detectronic Ltd / Lea Brook Valley CIO
Detectronic have been working with the Ribble Rivers Trust in Lancashire for over a Year, more recently with Yorkshire Water and the Lea Brook Valley CIO. The balancing ponds at Lea Brook Valley are currently owned by Yorkshire Water and have been since their construction in the early 1970s.
As Chair of Lea Brook Valley-CIO I have been involved with a great team of people helping to manage the site from an ecology and biodiversity point of view. Getting the right skill sets together from structural engineers, hydrologist and ecologist has been a rewarding challenge. The bigger challenge was getting the water companies, EA, LLFA and local community working together.
With the assistance of a Bio Diversity Fund and talks well on the way in regards to adoption of the SuDS/Wetland by the LBV-CIO for the community, things are looking much brighter.
Key learning points from this session:-
- Engaging community and stakeholders
- Getting facts and figures ready to speak the language
How constructed reedbeds contribute to biodiversity
Marie Athorn, PhD Student, University of Nottingham
Constructed reedbeds are artificial wetlands dominated by Phragmites australis designed to treat wastewater. They have been widespread in the UK because they are perceived to be a green solution, but their conservation value has never been assessed.
Marie Athorn will share the latest insights from a project aiming to determine how constructed reedbeds contribute to biodiversity. This study surveyed 24 sites, 12 constructed sites paired to 12 natural sites, for small mammals, moths and stem-dwelling invertebrates.
Latest insights into the UK’s working wetlands
Dr Chloe Hardman, Working Wetlands Development Officer, Wildfowl & Wetlands Trust
WWT has carried out a national survey of UK Working Wetlands. This focuses on wetlands that have been created or restored to help manage flood risk or improve water quality, alongside delivering biodiversity and visitor wellbeing or learning benefits.
There have been over 200 examples submitted, of which 36 are constructed wetlands for water quality. In terms of multiple benefits, 34 of these aimed to enhance biodiversity, five aimed to reduce flood risk and 22 aimed to provide visitor well-being or learning benefits.
The extent and quality of monitoring of multiple benefits and how this has been funded will be summarised in this talk. Case studies that demonstrate a high standard of delivery and monitoring of multiple benefits will be presented. A summary of the survey respondents ideas for policy changes to better support constructed wetlands will also be included.
One pond, two swales & two basins: a story about a retrofit SUDS using constructed wetlands
Stewart Moir, Moir Environmental
A case study of a retrofit SUDS project in Ayrshire from site investigations all the way through to completion. The key design issues, installation difficulties and practical solutions will be presented to give a real world overview of what it can take to implement a successful retrofit SUDS project using constructed wetlands.
Vertical flow wetlands for tertiary wastewater treatment in rural works
Dr Gabriela Dotro, Senior Research Fellow in Environmental Engineering, Cranfield University
Vertical flow (vf) constructed wetlands are typically used for secondary treatment of domestic wastewater where aerobic processes are needed. With tightening discharge consents in rural treatment works, there is an opportunity to adapt vf systems for tertiary treatment.
This study looked at the impact of loading rates and dosing frequency on treatment performance in eight pilot scale systems treating effluent from a trickling filter works, and compared it against three conventional tertiary technologies.
After an initial acclimation period, the wetlands delivered superior effluent quality to the other tertiary systems. The wetlands' performance was limited by the hydraulic conductivity of the media rather than oxygen availability for pollutant removal.
Design recommendations are proposed for tertiary application of the technology in rural works.
Combined Sewer Overflow (CSO) treatment by aerated wetland
Patrick Hawes, Wetland Wastewater Treatment Process Consultant, ARM Ltd
The use of aeration to enhance treatment performance levels of constructed wetlands is well understood. The effective use of wetlands for the treatment of combined sewer overflows (CSO) using passive wetland treatment systems has also been reported. This paper describes a CSO treatment wetland project in Cowdenbeath in Scotland which uses aerated reed bed technology.
The inherently variable nature of weather-based phenomena which gives rise to CSO flows and loads provides unique challenges in the wetland design. One of the advantages of aeration in this context is that the aeration system can be used intermittently, in response to short-term biochemical oxygen demand (BOD) and nitrification demands associated with CSO events. This minimises power consumption whilst allowing operational control of aerobic conditions within the wetland bed.
A new CSO collection main was constructed in Cowdenbeath, Scotland (population 11,000) by Scottish Water and a treatment wetland solution was proposed to manage and treat these additional loads. Modelled flow and load data was processed to characterise the frequency and size of daily events and their associated contaminant loads using probability distributions to finalise the design.
The design of the wetland balancing system, feed forward system and aeration control in response to variable wet weather flow, dry weather flows and periods of no flow are described.
Supercharging a surface flow wetland with pure oxygen: High-rate nitrification in a small area
David Austin, CH2M
Nitrification in treatment wetlands requires dissolved oxygen that passive wetlands cannot practically provide. Aerated subsurface flow wetlands (SSF) achieve high rates of ammonia oxidation, but are prone to clogging. Surface flow (SF) wetlands do not clog and cost about 60% less to construct than SSF wetlands, but are poorly suited to aeration. Pure oxygen injection overcomes this problem. This presentation documents performance of the first and only such system in operation.
An SF wetland (2.3 ha) in northern USA treats 800 m3/d of ammonia contaminated groundwater. Inlet ammonia-N is approximately 10 mg/L. Discharge is mostly non-detect. Water recirculates (3,000 m3/d) from the discharge end of the wetland to three midstream points. A downflow oxygen contactor (Speece cone) in line with the recirculation pipe supersaturates in-pipe water with dissolved oxygen (DO) to 80 to 140 mg/L, depending on water temperature. Wetland discharge is always at least DO saturated. When water temperatures drop to 0.5oC under the ice cover, nitrification degrades, but quickly recovers with small doses of nitrifying bacteria.
Preliminary modeling of observed reaction rates suggests that this wetland could treat 10,000 m3/d to 1 mg/L ammonia-nitrogen with an approximate 50% increase in oxygen supply. A passive SF wetland would need 119 ha. Modest treatment area requirements, simple infrastructure, high reliability, and low construction costs of oxygenated wetlands opens new opportunities for SF treatment wetlands.
Using Water Treatment Residuals as a reactive media to adsorb phosphorus from wastewater
Ben Gersten, Cardiff University
Water treatment residuals are a waste product produced by the water industry in vast quantities. This talk will discuss where these residuals come from and why they are good at removing phosphorus from wastewater. I will give a brief overview of the key results from my PhD and show how the residuals could be used directly in a wetland or as a pre or post filter to aid in the removal of phosphorus.
The practical development of Integrated Vertical Treatment Wetlands (IVTWs/ IVCWs) used for domestic wastewater treatment in Addis Ababa.
Girmaye Abebe, Addis Ababa University
IVTWs were implemented on one of the campus of the AAU, i.e. EiABC. The main objective of the research was to test the effect of different media on the treatment performance of IVTWs in the prevailing climate of Addis Ababa. Therefore, a gravel-filled wetland and a filter cake filled wetland were operated identically with domestic wastewater. All of the wetland cells were planted with C. papyrus.
According to the results, average removal inefficiencies for the filter cake and gravel wetland cells were feasible and promising in both summer and winter seasons with high treatment efficiency that fulfil the international standard to discharge to water bodies related to TSS, COD, BOD, TN, TP, and phosphate. The application of filter cake in the IVTWs has no significant impact on the treatment efficiency of the wetlands.
The current treatment system of condominium domestic wastewater i.e. SP has very low treatment efficiency than IVTWs.
Since this study was a pioneer for implementation of IVTWs in Ethiopia using local sources, it has proved that this eco-technology could also be used effectively for wastewater quality enhancement in Addis Ababa and other cities.
