Design and performance of an innovative hybrid constructed wetland for sustainable pig slurry treatment in small farms

Simple and suitable treatment of swine slurry from small farms is paramount especially in sensitive areas. This paper evaluates the viability of an innovative nature-based technology hybrid system (a Vertical Flow Constructed Wetland followed by a Horizontal Flow Constructed Wetland both planted with reeds - Phragmites australis) to treat swine slurry for further land application or discharge in water bodies with reduced nitrogen impact. Physicochemical parameters, bacterial indicators, surface deposits and biomass inside the filters were monitored. The hybrid configuration offered a dual function for simultaneous solid-liquid separation and biological treatment. Removal of organic matter and suspended solids was very high (>80% for SS and >75% for COD and BOD5) while the overall nitrogen load removal was 65%, due to the combined nitrification/denitrification processes, thus effectively reducing swine slurry nitrogen content. The influence of temperature and design and operational parameters on the treatment efficiency and the hydraulic behavior were also studied. The vertical constructed wetland achieved good hydraulic performance with no clogging problems, despite high pollutant loads. Some of the pollutants were retained and mineralized in the surface deposit layer, increasing around 20 cm each year. This organic biosolid layer improved filtration efficiency. The high ammonia contents interfered with the growth of Phragmites australis, while the high concentration of suspended solids and organic matter determine the operation and design to be implemented

Municipal Wastewater Treatment and Reuse for Agriculture in Senegal

This paper reports on the performance of using a multistage constructed wetland (CW) to treat municipal raw wastewater and an analysis of its suitability for agricultural irrigation. The pilot plant consists of two stages of vertical flow CWs plus one stage of a horizontal CW built in 2018 with diferent local materials at the Gaston Berger University Campus, Saint Louis (Senegal). Each CW stage is composed of several filters with di erent type of media (silex, granite, or river gravel), filtering media depths, and macrophytes (Phragmites and Typha). The physicochemical and microbiological indicators were monitored over six months at each bed inlet and outlet to evaluate the e ciency and achievements of the Senegalese, European, and WHO regulations/recommendations for disposal or reuse in irrigation. This study demonstrates the viability of this new multistage CW design to treat raw municipal wastewater and produce an e uent of good quality suitable for reuse in agriculture. The removal of organic matter, suspended solids, and nutrients was very high (>95% for SS, BOD5 and N-NH4 +, >90% for COD and P-PO4 3 as was the reduction of microbiological indicators (fecal coliform reduction >5 log units and helminth egg removal of 100%). First, trends related to the influence of design (the type of gravel, filter depth, and type of macrophyte), operational modes, and the CW treatment eciency were determined. The use of non-crushed gravel and Typha spp. seemed to provide better removal rates. On the contrary, no diferences were found between the use of silex or granite gravel. For the studied Senegalese conditions under dry and hot climates, the preliminary results indicate that no resting periods are necessary for vertical flow CWs (VFCWs), thus resulting in a reduction in construction and operation costs. The main outcome of our study is evidence that multistage CWs can provide robust, cost-efective treatments, as well as allow for safe water reuse, which is imperative in areas with severe water scarcity and endemic microbiological waterborne diseases

Subsurface flow constructed wetlands for the treatment of wastewater from different sources. Design and operation

[eng] The aim of the thesis is to examine the viability of the subsurface constructed wetlands for the treatment of wastewater derived from three different sources (treatment ponds, pig farms and car wash facilities), and to evaluate the influence of design (size, type and depth of media, presence of Phragmites australis) and operational parameters (hydraulic load, dosing and feeding modes) on treatment efficiency and hydraulic behavior. Several studies were done in the framework of different national and European R+D projects in 4 study sites. The viability of constructed wetlands with vertical and/or horizontal subsurface flow to treat the effluent from wastewater treatment pond systems (facultative and tertiary ponds) for discharge or reuse was evaluated in two municipal wastewater treatment plants, one in Aurignac (France) and the other in Santa Eugènia (Mallorca, Spain). The evaluation of the viability of hybrid subsurface flow constructed wetlands to treat swine slurry for land application or discharge in water bodies was performed in small farm was Can Corominas located in Viver i Serrateix (Barcelona, Spain). Finally, the viability of vertical and horizontal flow constructed wetlands to treat the effluent from car wash facilities for recycling was evaluated at a car wash station located in Montfullà (Girona, Spain), using an infiltration-percolation system as reference. A monitoring of the water quality (physicochemical and microbiological parameters) and the filters’ hydraulic (monitoring of flows, infiltration rates and tracer tests experiments) were performed. The main outcome of the thesis is the viability of the application of different configurations of subsurface flow constructed wetlands to treat the effluents from a wastewater treatment pond, a pig farm, and a car wash facility, once design and operation have been optimized. Subsurface flow constructed wetlands have shown resilience to load and hydraulic fluctuations, to new pollutants and to variable environmental conditions; being simple to operate and maintain with null or minimum energy requirements and with an added aesthetical value. From the case studies several points can be indicated as main conclusions. Paying special attention to the pond effluent study, it was characterised by a large quantity of algae and a high effluent variability that mainly depends temperature and solar irradiation. The experimental results demonstrated the effectiveness of vertical and horizontal flow constructed wetlands to upgrade pond effluent quality by retaining algae and suspended solids, completing organic matter degradation, and nitrifying the pond effluent in the case of vertical flow and partially removing total nitrogen in the case of horizontal flow. The filtering media size (sand or gravel) was the key parameter for algae retention. The presence of plants did not significantly affect the filter performance. The filtering media size (sand or gravel) was the key parameter for algae retention. The removal of microbial indicators depended mainly on the water retention time in the filter, which in turn depended on the media granulometry and hydraulic load, and on the depth of the filter and the dose volume per batch. The swine slurry presented high concentrations of suspended solids, organic matter, nitrogen and phosphorous, with high variability depending. The high ammonia contents interfered with the growth of Phragmites australis, while the high concentration of suspended solids and organic matter also limited the type of subsurface flow constructed wetland to be implemented. The hybrid configuration, which combines vertical and horizontal flow constructed wetlands, had a dual function for simultaneous solid-liquid separation and biological treatment. Removal of organic matter and suspended solids was very high, while the overall nitrogen load removal was around 65%, due to the combined nitrification/denitrification processes. The maximum number of feeding days was a key factor to avoid clogging. Some of the contaminants were retained and mineralised in the surface deposit layer of the vertical flow filter, increasing around 20 cm each year. Finally, car wash effluent had a high concentration of inorganic suspended solids, very variable concentrations of E. coli and organic matter, low concentrations of nutrients, and the presence of hydrocarbons, fats and oils and non-ionic surfactants. The three technologies evaluated performed very efficiently with respect to turbidity, organic material, and suspended solids. Non-ionic detergents, hydrocarbons, fats and oils were also completely removed, but their concentrations in the influent were already very low. E. coli was also removed to acceptable limits for recycling, with concentrations lower than the limits established in the Royal Decree guidelines for reuse in Spain. The oil and fats contents of the car wash effluents as well as the inorganic suspended solids made pre-treatment necessary in order to avoid media clogging. The low concentrations of nutrients resulted in a slow growth of Phragmites australis especially in horizontal flow constructed wetlands.[cat] L'objectiu principal de la tesi és l’estudi de la viabilitat dels aiguamolls construïts amb flux subsuperficial per al tractament d'aigües residuals de diferents orígens (llacunatges, granges de porcs i instal·lacions de rentat de cotxes), i avaluar la influència dels paràmetres de disseny i d’operació en l'eficiència del tractament i el comportament hidràulic. Els estudis experimentals es van realitzar en el marc de diversos projectes de R+D+I nacionals i europeus R+D+I. La viabilitat dels aiguamolls construïts amb flux subsuperficial vertical i/o horitzontal per al tractament dels efluents de sistemes de llacunatges (facultatiu i terciari) es va avaluar en dues plantes de tractament d'aigües residuals urbanes, a Aurignac (França) i a Santa Eugènia (Mallorca, Espanya). Per al tractament de purins es va construir una planta pilot d'aiguamolls de tipus híbrid en una granja situada a Viver i Serrateix (Barcelona, Espanya). Finalment, es va realitzar un estudi de la viabilitat dels aiguamolls construïts de flux vertical i horitzontal per al tractament i reciclatge dels efluents d’instal·lacions de rentat de cotxes en una estació situada a Montfullà (Girona, Espanya), utilitzant un sistema d'infiltració-percolació com a referència. Es va fer el seguiment de la qualitat de l'aigua (paràmetres fisicoquímics i microbiològics) i de la hidràulica d’aquestes tecnologies (control de cabals, velocitats d'infiltració i experiments amb traçadors). La principal conclusió de la tesi és que l'aplicació de diferents configuracions d’aiguamolls construïts de flux subsuperficial per tractar els tres tipus d’aigües residuals estudiades és viable, malgrat que se n'ha d'optimitzar el disseny i l’operació. S'ha constatat que els aiguamolls construïts de flux subsuperficial vertical i horitzontal milloren la qualitat dels efluents de llacunatges, mitjançant la retenció de les algues i dels sòlids suspesos i completant la degradació de la matèria orgànica. La granulometria del medi filtrant és un paràmetre clau per a la retenció d'algues. L'eliminació dels indicadors microbiològics depèn principalment del temps de retenció d'hidràulica, que depèn, alhora, de la granulometria dels filtres, de la profunditat del medi, de la càrrega hidràulica i del fraccionament d’aquesta. Per altra banda, la configuració híbrida d'aiguamolls construïts, que combina flux vertical i horitzontal, presenta uns elevats rendiments d'eliminació de matèria orgànica i sòlids en suspensió dels purins. El nitrogen s'elimina al voltant del 65% gràcies als processos combinats de nitrificació (al filtre vertical) i desnitrificació (a l'horitzontal). L’elevada concentració d'amoníac dels purins va interferir en el creixement de Phragmites australis. Alguns dels contaminants van ser retinguts i mineralitzats i van formar una capa a la superfície del filtre de flux vertical. Aquesta capa ajuda a la depuració augmentant la filtració i els temps de retenció hidràulica, però cal limitar-ne el creixement mitjançant el control de la càrrega orgànica i dels períodes de descans per tal que no es produeixi una disminució massa gran de la infiltració. Finalment, les tres tecnologies avaluades per tractar els efluents de rentat de cotxes van resultar molt eficients pel que fa a la reducció de la terbolesa, de la matèria orgànica i dels sòlids suspesos. Els detergents no iònics, els hidrocarburs, els greixos i els olis també es van eliminar completament, però les seves concentracions en l'influent eren molt baixes. L’eliminació d’E. coli també va resultar elevada, especialment al sistema d’infiltració-percolació i a l'aiguamoll construït de flux vertical, de manera que es van assolir límits de qualitat aptes per al reciclatge. Les baixes concentracions de nutrients van donar com a resultat un creixement lent de Phragmites australis. El contingut d'oli i de greixos d’aquests efluents, així com els sòlids inorgànics en suspensió, fan necessari un pretractament