Optimizing resource recovery from wastewater with algae-bacteria membrane reactors

Exploiting the combination of algae and bacteria in High Rate Algal/Bacterial Ponds (HRABP) is an emerging approach for wastewater remediation and resource recovery. In this study, the advantage of adding a solid/liquid separation system to uncouple Hydraulic Retention Time (HRT) and Solid Retention Time (SRT) is explored and quantified. A long-term validated model for HRABP was run to simulate and optimize a system at large scale treating digestate. It is shown that by uncoupling HRT and SRT, adapting the liquid depth and the alkalinity content, the algae productivity increases from 9.0 to 14.5 g m(-2) d(-1) (for HRT = SRT in the range of 5 to 10 days) to 20.3 g m(-2) d(-1) (for HRT = 0.2 d and SRT = 2 d). Simulations pointed out that maximizing the algal pro-ductivity or the fraction of recovered nitrogen in the algal biomass are conflicting goals that are achieved under different operating conditions. Conditions maximising the algal productivity favour algae and heterotrophic bacteria while algae and nitrifying bacteria dominate the system under those conditions optimizing the efficiency of nitrogen recycling. Finally, increasing the influent alkalinity and adapting the water depth can boost the algal productivity without meeting conditions favourable to N2O emission, opening new perspectives for resource recovery through algal biomass valorisation

Traitement biologique aérobie du lisier de porcs : performances des systèmes de séparation de phases et caractéristiques des co-produits

Les performances de quatre stations de traitement biologique aérobie du lisier de porcs ont été déterminées à travers la répartition des principaux éléments tels que l'azote, le phosphore, le potassium, le cuivre et le zinc dans les co-produits. Différents séparateurs ont été évalués au cours de ce travail : vis compacteuse et centrifugeuse pour la séparation du lisier brut et filtre à bande sous vide pour la séparation du lisier aéré. Dans tous les cas, 60 à 70 % de l'azote sont éliminés sous forme gazeuse. L'utilisation d'une vis compacteuse pour séparer le lisier brut permet de capter, dans la phase solide, une partie des éléments non biodégradables tels que le phosphore (20-25 %), le cuivre et le zinc (8-10 %). Les performances de séparation sont plus importantes avec l'utilisation d'une centrifugeuse et peuvent atteindre 80 % pour le phosphore et 50-70 % pour le cuivre et le zinc. L'utilisation d'une vis compacteuse pour la séparation du lisier brut et d'un filtre à bande sous vide pour la séparation du lisier aéré, permet de capter 90 % du phosphore et la totalité du cuivre et du zinc. Les caractéristiques des différents produits solides obtenus ont été déterminées au cours de cette étude. Les concentrations en cuivre et en zinc sont importantes et peuvent atteindre 96 gCu/tonne et 194 gZn/tonne pour le refus issu de la centrifugeuse et 140 gCu/tonne et 342 gZn/tonne pour la phase solide issue de la filtration sous vide du lisier aéré. / The efficiency of four biological aerobic treatment units was studied as regards nutrient removal performances and repartition of compounds (nitrogen, phosphorus, potassium, copper and zinc). Several type of separators were evaluated : press-auger separator and decanter centrifuge for the separation of the raw slurry and vacuum sieve-belt separator for the separation of the aerated slurry. Between 60 and 70% of the nitrogen was removed in gaseous form. The separation efficiency for the press-auger was 20-25% for phosphorus and 8-10% for copper and zinc. Efficiency was improved with the use of the decanter centrifuge and could raise 80% for phosphorus and 50-70% for copper and zinc. With the use of press-auger for the separation of the raw slurry and vacuum sieve-belt for the separation of the aerated slurry, 90% of phosphorus and the totality of copper and zinc were concentrated in the solid phases. By-products characteristics were obtained during this study. Copper and zinc concentration up to 96 gCu/ton and 194 gZn/ton for the solid phase from the press-auger separator and 140 gCu/ton and 342 gZn/ton from the vacuum sieve-belt separator were obtained

Combined anaerobic digestion and biological nitrogen removal for piggery wastewater treatment: a modelling approach

International audienceIn order to deal with the environmental problems associated with animal production industrialization and at the same time considering energy costs increasing, a piggery wastewater treatment process consisting of combined anaerobic digestion and biological nitrogen removal by activated sludge was developed. This contribution presents a modelling framework in order to optimize this process. Modified versions of the well established ASM1 and ADM1 models have been used. The ADM1 was extended with biological denitrification. pH calculation and liquid gastransfer were modified to take into account the effect of associated components. Finally, two interfaces (ADMtoASM and ASMtoADM) were built in order to combine both models. These interfaces set up the COD, nitrogen, alkalinity and charge fractionation between both models. However, for the mass balances between both models, some hypotheses were considered and might be evaluated

Monitoring GHG from manure stores on organic and conventional dairy farms

Organic farming methods are claimed to be more environmentally friendly than conventional methods and the EU MIDAIR project had an overall aim to compare emissions from organic dairy farming with conventional methods of milk production. Manure stores are the second largest source of methane emissions (after enteric fermentation) on European dairy farming. The aim of this project was to measure green house gas (GHG) emissions from manures in covered and uncovered slurry stores and farm yard manure (FYM) heaps. The chosen method for measuring these emissions was the tracer ratio method, using sulphur hexafluoride (SF6) as the tracer gas, the limitations of this method prevented successful measurements being made on some of the stores and a modified method was used on the covered stores. The difference in concentration of the upwind and downwind samples and interfering sources were limiting factors. FYM emission measurements were successful only when the manure was stored indoors. Methane emissions were successfully measured over a 12 month period from the uncovered slurry stores. Emission rates from the uncovered slurry stores on the conventional farm and the organic farm ranged from 14.4 to 49.6 and from 12.4 to 42.3 g C m(-3) d(-1), respectively, with the mean CH4 emission rates of 35 and 26 g C m(-3) d(-1). On both farms, nitrous oxide emissions were close to zero. Methane emissions measured from the indoor organic FYM in summer were 17.1 g C m(-3) d(-1) and the nitrous oxide emission was 411 mg N m(-3) d(-1). The covered slurry stores were in such close proximity to other GHG sources that the tracer ratio method was unsuitable and the air-injection method was adopted. The measured emissions from covered slurry stores of CH4, CO2 and NH3 were, respectively, 14.9 g C m(-3) d(-1), 12.9 g C m(-3) d(-1) and 18.6 mg NH3 m(-2) d(-1) of slurry in February and 12.0 g C m(-3) d(-1), 9.5 g C m(-3) d(-1) and 335 mg NH3 m(-2) d(-1) slurry in March. No nitrous oxide production could be measured. (c) 2005 Elsevier B.V. All rights reserved

Nitrogen transformations and ammonia loss following injection and surface application of pig slurry: a laboratory experiment using slurry labelled with 15N-ammonium

A laboratory experiment was designed to determine the fate of 15N-labelled slurry ammonium (15NH4-N) and compare soil inorganic-N distribution following surface applied or injected pig slurry. A system of cylindrical volatilization chambers equipped to allow continuous trapping of ammonia (NH3) was used. Undisturbed soil columns were placed in the chambers prior to the application of slurry. A nitrogen balance including soil, air and plant analysis was established for both treatments, 8 days after application. Average cumulative emissions of NH3 were 15% and 11% of the total ammoniacal-N added with the surface and injected treatments, respectively. After 8 days 55% of the 15NH4-N applied through slurry injection was recovered in the soil inorganic-N pool: 37% as 15NH4-N and 18% as 15NO3-N. These figures compare with only 25% 15NH4-N recovered with the surface applied slurry treatment: 7% as 15NH-N and 17% as 15NO3-N. Immobilization into soil organic-N accounted for 8% of the 15NH4-N applied for the injected treatment and 6% of the surface applied slurry-15N. 15N uptake by the grass was 2% and 7% for the injected and surface applied treatments, respectively. The percentage of added 15N accounted for was 76% for the injected treatment and 53% for the surface applied slurry treatment.</jats:p

Nitrite effect on nitrous oxide emission from denitrifying activated sludge

International audienc