Nowak J.1,2, van Afferden M.3, Albold A.4, Bernhard K.4, Fehr G.5, Galander C.6 Hasselbach R.7, Heise B.8, Kühn V.9, Langergraber G.10, Molle P.11, Nivala J.3, Rustige H.2, Stockbauer M.12
1Fachhochschule Potsdam, Potsdam, Germany
2AKUT Umwelt, Berlin, Germany
3Helmholtz Center for Environmental Research– UFZ, Leipzig, Germany
4Otterwasser GmbH, Lübeck, Germany
5KED GmbH & Co., Langenhagen, Germany
6Umweltbundesamt – UBA, XXXXX, Germany
7Entsorgungsverband Saar – EVS, Saarbrücken, Germany
8Staatliches Amt für Landwirtschaft und Umwelt, Neubrandenburg, Germany
9Stadtentwässerung Dresden GmbH Technical University of Dresden, Dresden, Germany
10Universität für Bodenkultur Wien – BOKU, Vienna, Austria
11Irstea, Lyon, France
12Bayerisches Landesamt für Umwelt, Augsburg, Germany
Keywords:constructed wetland, design, guideline
Abstract
The German guideline for the dimensioning, construction, and operation of constructed wetlands for biological treatment of domestic and municipal wastewater, which last published in March 2006, is being updated. The guideline applies to small wastewater treatment systems of less than 50 Person Equivalents (PE) apart from EN 12566-3, municipal treatment plants (with combined or separated sewers), treatment systems which use constructed wetlands as a polishing step, and small wastewater treatment systems which are operated seasonally (summer months only).
The revision is based on a wide range of experience gained in recent years in the use of treatment wetlands in Germany and in Europe. Prior to the revisions, the proposed changes were discussed in a public hearing in Potsdam, Germany in January 2014. The final revisions were released for public review in April 2016. The comments from the public review were submitted in written form to the DWA working group in late 2016, and a follow-up meeting was held in early 2017. The finalized document is anticipated to be put into effect in mid-2017.
Several constructed wetland designs appear for the first time in the new guideline. Two-stage unsaturated vertical flow gravel filters which receive raw wastewater in the first stage (based on experience in France) as well as two-stage unsaturated vertical flow filters receiving primary-treated wastewater (based on experience in Austria) are now included. The revisions also include new dimensioning for unsaturated vertical flow filters with lava sand as the main treatment media, as well as aerated treatment wetlands, both as secondary treatment steps.
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Recommendations are also provided for seasonally operated constructed wetlands, as well as constructed wetlands for graywater treatment. With the publication of the new guideline, horizontal subsurface flow constructed wetlands are no longer supported as a secondary treatment stage in Germany, and are recommended only as a tertiary or polishing stage.
Existing horizontal subsurface flow wetlands may continue operation, provided the systems are not hydraulically or organically overloaded, and that they continue to receive routine operations and maintenance. This presentation will outline the key points of the newly revised DWA-A 262 German constructed wetland guideline.
On-site wastewater treatment in France: statistical analysis of the outlet effluent quality of 240 facilities
Ref # Olivier_S2Small2017 L. Olivier1*,C. Boutin1
1 Freshwater systems, ecology and pollution research unit, IRSTEA, 5 rue de la Doua, CS 70077, 69626 Villeurbanne, France
*Corresponding author: laurie.olivier@irstea.fr
Keywords:COD, Comparison, Nitrogen, On-site treatment, Statistic, Wastewater treatment.
INTRODUCTION
On-site sanitation refers to systems used for the treatment of wastewater from individual houses.
Almost 5 million of on-site wastewater treatment systems are listed in France.
France issues approvals based on a close analysis of the European Commission (EC) marking test results (EN 12566-3) or following a similar procedure for systems without EC marking. Until 2009, only 4 “traditional” systems using soil treatment, sand or zeolite filters were allowed.
Latest changes in French regulation have permitted the commercialization of new systems: in 2017, more than 600 approvals from 60 constructors were issued in France. All systems are based on known processes in wastewater treatment and can be gathered in 3 processes families:
Attached Growth Systems on Fine Media (AGSFM), Biofilm Systems (BS), or Activated Sludge Systems (ASS).
An assessment of on-site sanitation systems began in 2011 to evaluate their efficiency. Data were collected from 240 on-site sanitation facilities in 22 French departments which cover 5 of the 6 Water Agency territories. The parameters analysed at the outlet are TSS, COD, BOD5, NH4+-N, NO3--N and TKN.
The aim of this article is to describe the outlet effluent quality and explain the data dispersion by analyzing the impact of explanatory variables such as i) the sampling method, ii) the treatment processes, iii) the applied organic load, iv) the aging and v) the maintenance.
MATERIAL AND METHODS
During 6 years, more than 1300 data were collected under standard conditions with two different sampling methods: 24h composite sample or punctual sample.
A methodology to validate data was developed by Irstea and has permitted to remove 11.8% of data; therefore the data analysis was carried out on 1286 validated data.
Among the 3 families (AGSFM, BS and ASS), 13 treatment processes were identified to gather systems based on common design characteristics such as the media (sand, zeolite, rock wool…).
The organic load was not measured. Therefore, the daily load (in COD) has been recalculated based on the number of inhabitants, their activities (at home all day or outside) and the amount of pollution per person per day. A loading rate is established from the nominal capacity.
The studied facilities are between 1 year and 12 years old which permits to study the aging of the systems over time.
The dataset obtained is heterogeneous i.e. different sampling methods, different wastewater treatment processes and a variability in the number of data per installation. Therefore, a statistical methodology has been implemented to compare systems within each other via an analysis of outlet concentrations of 6 parameters also called dependent variables (TSS, COD, BOD5, NH4+ -N, NO3--N and TKN).
The two types of sampling, the different treatment processes, the recalculated loading rate and the aging are identified as explanatory variables; they enable to explain the outlet effluent quality.
Each dependent variable has a quantification limit below which no value can be measured (i.e.
left-censored data). The only statistical methodology which allows to process left-censored data is the analysis of generalized log-linear model.
The equation of the model is:
log(ܻ) = ߤ+ݏ × ߱ With:
x Y : dependent variable
x μ : UHJUHVVLRQOLQHȕ0 ȕ1.X1 + …) where Xi DUHH[SODQDWRU\YDULDEOHVDQGȕi are the model coefficients
x s : dispersion parameter x ߱: normal residual error
In each subset of data (3 families, 13 processes, 32 systems), the model will identify the significant effects of explanatory variables for each of the 6 dependent variables.
Another methodology has been implemented to assess the frequency of the sludge emptying and the corrective maintenance of 170 facilities based on the analysis of qualitative data by the “fuzzy logic”. This method analyzes rules created from sanitation expert judgment and compares the different levels of maintenance from each family, process and system.
MAIN RESULTS AND CONCLUSIONS
Table 1 presents the number of validated data collected until 2016 for each process and family (1286). Between 2011 and 2016, 778 punctual samples and 508 24h composite samples have been collected. These processes have already been compared in terms of infiltration surface and daily applied surface organic load (Dubois 2017).
Table 1: Number of data collected until 2016 for each family and each type of process
Attached Growth Systems on
Fine Media Biofilm Systems Activated Sludge Systems
Media Number Types Number Types Number
Sand 149
Fixed bed 368 Classical* 37
Constructed wetlands 126
Without I settlement tank 84
Zeolite 139
Fluidized bed 13
Rock wool 102 With additional treatment 26
Coconut shaving 93
Biological discs 7
Pine barks 3 SBR 139
TOTAL 612 TOTAL 388 TOTAL 286
*Classical = I settlement tank + biological reactor + II clarifier
High variability in outlet concentrations was observed; the TSS concentration can be 160 times higher than the median value and 33 times higher for COD concentration.
The model shows significant differences between the 3 families, 13 processes and 32 systems.
These results are easily explained by the pollution degradation processes.
Due to a large amount of data and a wide range of stakeholders involved, this study would have a large impact on on-site sanitation in France and in Europe.
Data processing and results interpretation will be completed in September. Results of the study will be presented for the first time during the on-site sanitation conference (Assises de l’ANC) in September 2017 in France and will be published shortly afterwards.
REFERENCES
Boutin, C. Dubois, V. and Lassablière, C. 2013 Comparaison théorique de dispositifs d’ANC: les cultures fixées sur support fin autorisées au 1er novembre 2013 (Theoretical comparison of on-site sanitation systems: Attached Growth Systems on Fine Media approved before 1st of November 2013), Onema publication. 104 p.
Dubois, V., Boutin, C. 2017 A Comparison of the Design Criteria of 141 On-Site wastewater Treatment Systems Available on the French Market, Journal of Environmental Management (article in press)
Dubois, V., Chavarria, R., Boutin, C. 2014 Comparaison théorique de dispositifs d'ANC: les filières par "cultures libres" autorisées au 1 août 2014 (Theoretical comparison of on-site sanitation systems: Activated Sludge Systems approved before 1st of August 2014), Onema publication. 74 p.
Guillaume Serge et Charnomordic Brigitte. 2011 Learning interpretable Fuzzy Inference Systems with FisPro, International Journal of Information Sciences, doi:10.1016/j.ins.2011.03.025, 181(20), 4409-4427.
Hill Catherine, Analyse statistique des données de survie (Statistical analysis of survival data), Médecine-Sciences, Paris, 1999, ISBN 2257123107, 190 p.
MEDDE 2014 Agréments des dispositifs de traitement en France : site du Ministère de l’Environnement (Approvals of on-site sanitation systems in France: website of the Ministry of the Environment), http://www.assainissement-non-collectif.developpement-durable.gouv.fr/agrement-des-dispositifs-de-traitement-r92.html (accessed 06 July 2017)
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