This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Separación física de purines: un gran paso para su tratamiento y gestión medioambiental

Physical separation of purines: a big step for his treatment and environingingmental gestión

Josep Turet, Anna Busquets and Nuria Bruch (SART Medi Ambient of the University of Vic)

25/06/2013

Manure, commonly called manure or slurry according to water content, are by-products of livestock and consist mainly of feces and urine of animals, components that are associated with other materials used indoors, such as bed, cleaning water and food debris. Traditionally, family-type farms produced about manure with a low water content and therefore easily stackable in the beetles, where processes of decomposition and microbial stabilization were given and, when farmland could need them, used as fertilizer. These manure had and have clearly interesting characteristics for use as agricultural fertilizers (Pomar, 1984;) DARP, 1998; Sana et al., 1998).

Introduction

They are different Spanish communities which are among the areas in which livestock activities have become intensive, with a great development during the second half of the 20th century. Note the large increase of the pig population, which has led to high current census (DAAM, 2013;) MAGRAMA - technical General Secretariat, 2003). This step to intensive farming, focused on the maximum production and the importation of raw materials for livestock feed, has resulted in obtaining large quantities of manure and has unbalanced, in some areas, the relationship between the production of manure or slurry and the requirements of fertilizers for agriculture. This implies that these materials pass to have the connotation of surplus materials and, therefore, waste.

Perhaps most visible case also occurred in pig farming, in which the estabulaciones "bed" was replaced fairly quickly by the grids, or "eslats" with bottom trench and, in addition, the manual collection of the dejections spent cleaning the stables with pressurized water. This fact led to the emergence of a new type of manure: manure liquid or "slurry", which occurs in large volumes which further aggravate the problem. Anyway, these slurry still, if they are used rationally, ideally suited as fertiliser.

Either way, manures in swine, as a good example of manure that have caused environmental problems in different places of the world, are presented as a heterogeneous material in its composition, with a concentration of nitrogen (in N-Kjeldahl) usually located between 4,000-8,000 mg/kg (Turet et to the.)1992; Garcia, 1997; Turet i Vilalta, 1997). This nitrogen from manures is basically in two molecular forms: the inorganic ammoniacal (from 60 to 75% of the content) and organic (practically all the remaining quantity), so the presence of nitrates and nitrites tends to be relatively scarce. Despite this, the biological activity in aerobic environments, as agricultural soils or water courses, leads to further nitrification of these major forms of manure, and the resulting nitrate is assimilation by plants, and also may increase its concentration in the surface water or groundwater (Figure 1) in little or a lot, with a potential environmental impact.

Figure 1: Schema transformations and major destinations usually resulting from the contributions of swine manure on cropland. Decoding: N-org: organic nitrogen, N-NH₄⁺: ammoniacal nitrogen NH₄⁺: ammonium, NO₂ : nitrite, NO₃ : nitrate.

The existence of farms with a surplus pig population, regarding the assimilation capacity of manure from their fields, as a result implies a possible impact environmental or, on the contrary, the implementation of a strategy of treatment and/or timely and appropriate management of the same. The aim of this article is the present some of the results of the tests carried out in a treatment facility on farm for the physical separation of fractions of swine manure, treatment that appears as a big first step for the management and valorization of the slurry.

Technology of treatment

The system of treatment of manure that has been studied belongs to technologies mécaniques Segalés, S.L., located in porcine cattle Gili exploitation of the municipality of Seròs (Lleida) and is based on three physical phases separation processes, installed in series.

The line of flow of the treatment (Figure 2) chains, an initial reception and homogenization (1) stage, which stores the waste water influent to the treatment (PI), cushioning the variations in the composition and avoiding the sedimentation of solids, and triple separation (2) treatment, resulting in a final effluent that is stored on a raft (3) to be used for fertiirrigacion.

Figure 2: General flowchart of the treatment of separation of fractions studied. Decoding: 1: deposit receipt and homogenization, 2: multiple treatment process, 3: raft for effluent, FR: filtro-rampa, SP: pressure, Rseparator: Rotary filter, PI: influent slurry treatment, FLF: liquid fraction of the filtro-rampa, FSF: solid fraction of filtro-rampa, FLS: liquid fraction of the separator's pressure, FSS: solid fraction of separator pressure, FLR: liquid fraction of the Rotary filter, FSR: solid fraction of Rotary filter and df *: optional destination of the liquid fraction (the Rotary filter or field).

The first step of this multiple system of treatment (figure 3), the purín drives by pumping to the first separation by filter-rampa (figure 4), that acts by gravity, obtaining, on the one hand, a solid fraction (FSF) of spongy appearance and of a high content hídrico, and a liquid fraction filtered (FLF), that could be already directly the final effluent or, in this case present, be driven to a rotary presses filter (step of mesh of 250 micras) to suffer a second leak. It can have, therefore, a destination facultativo (df *).

It appears 3: general Sight of the installation of treatment of the pork exploitation Won Gili of the municipality of Seròs (Lleida).

Figure 4: System of 'filtro-rampa' made by Mecàniques Segalés, consisting of ramp (s) filter with stainless steel sifter of 0.65 mm pitch of mesh, cleaning brushes powered by engines of 0,25 kW and a screw conveyor that pushes solid until the separator.

The solid fraction of filtration (FSF) becomes a separator pressure (figures 2 and 5), where a liquid fraction (FLS) following treatment and a solid separation (FSS) look much more dry and a holding capacity of water higher than the treated solid fraction is obtained. The liquid fraction obtained in this separative process is linked to a new operation of separation by the Rotary filter (with a step of 250 µm mesh), but it could also be considered as a final effluent, and can be mixed with the liquid system of previous filtro-rampa fraction (will call to this mix as a global liquid fraction or FLG).

Figure 5: Separator pressure MS-300 stainless steel manufactured by Mecàniques Segalés, powered by a 5.5 kW motor, of thread reinforced with tungsten, a mesh sieve triangular counterweight's pressure to the gates of the solid fraction and 0.5 mm pitch.

The last operation of separation, by means of the Rotary filter (figures 2 and 6), one of the liquid fractions or, in the case which concerns us, the mixing of the two (FLG) has the objective of ensuring a maximum size of suspended particles to prevent fillings for the application of liquid fertilization system here. Therefore, it is simply a final tune-up treatment. The solid fraction (FSR) of this filter, visual appearance liquid, is returned to plant (deposit of homogenization) header.

Figure 6: Roto-RFT2000 fully stainless steel filter manufactured by Mecàniques Segalés powered by an engine of 1.5 kW with a mesh sieve triangular with a 0.25 mm step

Treatment works seasonally as the manure management requires it. The flow of treatment for this study was approximately 45 m³h.

Methodology of the essay

Splitting of the plant in operation continued, realizar an integrated sampling for each one of the substrates of entrance and exit of the different technological elements of the system of treatment. The intervals of time for the taking of the submuestras integradoras of the final samples were of 30 minutes roughly during a global time of the essay of 3 hours.

The different samples obtained moved in isothermal sensors container to the Laboratories SART of the University of Vic (Barcelona) and stored in conditions of refrigeration for the realisation of all the analytical determinations programmed. The types of substrates muestreados and the determinate analytical parameters come exposed in the table 1.

Table 1: Parrilla of the analytical characterisation effected of the samples.

The analytical methodologies used (table 2), have been the standard for this type of samples and have been based in the ' Standard Methods for the Examination of Water and Wastewater' [APHA, AWWA, WEF, 1995].

Table 2: Summary of them methodologies used in the analytical parameters.

Results

The results of carried out analytical determinations that are of interest to this article are set out in table 3.

Table 3: analytical results of characterization.

The influent slurry

The slurry entered the system (table 3 PI) has presented a relatively low content in solids (ST 37 g/kg) and in an advanced state of mineralization, so the proportion of organic matter is low (SV/St. close to 50%) i the relative content of nitrogen as ammonia is high (N-NH4 + / NKT 77.6%). Efficiencies and yields of the different physical treatments of separation of fractions would under these conditions, be located in their values lower than the ranges in which usually move, and therefore provide us with results that guarantee the minimum to reach in the general use of the technological solutions that we present here.

Results from other analytical parameters, whereas the effects relating to the conditions expressed in the previous paragraph, correspond perfectly to the normal characteristics of liquid swine manure of bait (SART Medi Ambient, 2013).

Filtration on ramp

The same table 3 shows the results obtained in two fractions (FSF and FLF) filtration process in the 'filtro-rampa' of mechanical Segalés, which provide the efficiencies of reduction in the liquid fraction exhibited in table 4.

Table 4: efficiencies of reduction of various parameters evaluated in trials of filtration on ramp (mechanical Segalés, S.L. filtro-rampa), by comparing the obtained liquid fraction (FLF) in relation to the influent tested slurry (PI).

Note relatively high reductions in the concentration of solids that provides this filtration technology by gravity. Not only are talking about solid particulates in suspension (SST and SSV,) with reductions exceeding 20% of its concentration, but also of other smaller constitutional materials which, to form partnerships between different components, we are retained in the separate solid fraction. Globally, obtained reductions of 30% and 34% in total and volatile solids (ST and SV), respectively, which involve a very significant reduction of the cod of the pollutant load of manure measure, 48%.

Obviously, the interest of a swine farm surplus in cattle manure on the requirements of the agricultural fields that have fundamentally lies in reduce phytonutrients and thus achieve a rational fertilization, and, currently, especially in nitrogen. The results obtained in this element are not as spectacular as in other parameters, but interesting, since close to 18% efficiencies mean that exploitation, managing export solid fraction obtained, reduces most of the useful agricultural surface ratios you need for these cattle manure (see paragraph 4 yields). Also 23 and 19% reduction efficiencies are should highlight to the P and K, respectively.

Treatment with pressure separator

The separator filter with pressing (Figure 5) system is ideal, in general, to obtain solid fractions of high concentration and can be used in the treatment of slurry and manure, both different types of very wet solid fractions. The latter case is now occupied us, the solid fraction obtained from the filtro-rampa (FSF) treatment, although we can serve to visualize the effect of this separator system in general.

The results of this process are presented in table 3, from which the reduction efficiencies set out in table 5 are calculated, and in addition, the following conclusions are obtained:

The separator solids handling of a solid fraction to get another more concentrated has shown very good results, since the efficiencies of reduction on the entry (FSF) substrate, whereas the resulting liquid fraction (FLS) have been high (about 74 and 82% for the ST and SV, respectively).
The solid fraction obtained (FSS) shows characteristics in concentration of solids (23% WT/WT) making it manageable and stackable for storage or for composting. It has more than doubled the concentration of solids from influent material, as well as other parameters (such as phosphorus).
You get a liquid fraction (FLS) of similar characteristics (with similar charges) to the resulting from the filtro-rampa, so that you can mix without any prejudice for use or treatment.

Table 5. Efficiencies of reduction of various parameters evaluated in the trial of treatment with pressure separator, by comparing the obtained liquid fraction (FLS) in relation to the tested influent substrate (solid fraction of filtration on ramp: FSF).

This treatment allows for obtaining materials of solid consistency, easy management for export of farms and, moreover, without producing liquid effluents with higher loads with respect to those obtained in the filtro-rampa.

Treatment with rotary filter

Liquid fractions obtained from the two systems evaluated may be refined to a specific re-use, but, in the majority of cases, this operation will not be needed. He case consists in the use of a rotary filter a mesh of 250 micrometers to treat liquid fractions obtained from the two preceding processes, with the aim of guaranteeing a maximum size of particles in the effluent for liquid fertilization.

The results achieved are those set out in table 3 (FLR and FSR), but Mission of this article is not evaluative analysis of this particular and specific process of exploitation that has this facility.

Aspects to be noted by way of conclusions

It should, finally, to combine the data of different treatments to obtain final definitive visions. So the two points that follow are:

I. the visualization of the effects obtained in liquid fractions or liquid effluents resulting from the three types of tested separators, in relation to the treated manure, are presenting the figures that follow (figures 7, 8 and 9). The obtained liquid effluents are very similar each other, result that allows, according to the objectives to be pursued, the selection of unique treatments or, as is the case of our experimental exploitation, varying combinations with subsequent mixture of liquid effluents.

Figure 7: General histogram of the contents in total solids (ST), and volatile solids (SV) tributary treated manure (PI) and the different effluents (liquid fractions) obtained in each treatment: FLF for filtration in ramp, FLS for separator's pressure and FLR Rotary filter.

Figure 8: General histogram of content on chemical oxygen demand (COD) and total nitrogen Kjeldahl (NKT) tributary treated manure (PI) and the different effluents (liquid fractions) obtained in each treatment: FLF for filtration in ramp, FLS for separator's pressure and FLR Rotary filter.

Figure 9. General histogram of content in ammoniacal nitrogen (N-NH₄^₊), total phosphorus (P) and potassium (K) tributary treated manure (PI) and the different effluents (liquid fractions) obtained in each treatment: FLF for filtration in ramp, FLS for separator's pressure and FLR Rotary filter.

The questions that do us immediately in front of one of these processes of physical separation refer to the degree of purification that provide us like pre-treatments. The figure 8 sample the comparative of the chemical demand of oxigeno (DQO) and the total nitrogen Kjeldahl (NKT). It is notorious that, if we compare the liquid fractions with the purín influente of which come from, the reduction in DQO is very high, near to 50% of the initial content. By his part, the N has suffered a relatively lower variation in his concentration of these liquid fractions with regard to the one of the purín, so that only they can use values of next reduction to the 15-20%.

Is essential to refer also to the nutrients for the vegetal crops (the fitonutrientes) and especially to which need of majority form (the macronutrientes): N, P and K. Considering those that will have a relatively fast effect on the vegetables, the N-amoniacal (N-NH₄^₊) and good part of the P and the K in the purines, the figure 9 sample that the three fitonutrientes conserve mostly in the liquid fractions obtained, and that his reductions with regard to the purín tributary situate between a 18 and 23% (can generalise in 15-25%) and the greater retention always produces in the P.

If it thinks in the liquid fractions like fertilizantes liquid, the relations between the macronutrientes in N (in NKT):P:K would situate near of 3,0:1,0:1,8.

II. not only are interested in liquid fractions concentration reduction efficiency obtained, but that, considering the volumes distributed between the two fractions, are fundamental to management in livestock treatments reducing yields. The mathematical expression for these reduction yields is:

Indicative level and for the filtro-rampa, calculations of yields of reduction in liquid fractions on the influent slurry translates into table 6 intervals (to more trials, higher will be the guarantees of inclusion within the ranges). In this case, and after what already we have outlined, no further comment is needed, maybe these yields correspond directly to reductions of each parameter to be gained on the holding (or, in general, the producer of that waste entity), provided that you can export the solid fraction obtained. Thus, management strategies of the solid fractions obtained in physical systems of separation of fractions become key points for the reduction of nutrients in livestock farms.

Table 6: reduction yields estimated at different parameters evaluated in the trial of filtration in ramp, comparing the liquid fraction obtained in relation to the influent tested slurry (PI).

Bibliography used and complementary

-Auger, r., Turet, j., Busquets, a., Farrés, M., Font, x. & Sánchez, a. (2011). Respirometric screening of several types of manure and mixtures intended for composting. Bioresource Technology, 102: 1367-1377

-DAAM (2013). Statistics Metropolità. http://www20.gencat.cat/portal/site/DAR/ Departament D'agricultura, Ramaderia, fishing, Alimentació i Medi Natural (Generalitat de Catalunya).

-DARP (1998). CODI de bones pràctiques agràries in relació amb the nitrogen. Order of 22 October 1998. Departament D'agricultura, Ramaderia i fishing. Diari Oficial de la Generalitat de Catalunya.

-Espona, j., Turet, j. and Viver, j. (1995). Forced aeration of pig manure in semi-continuous regime. Water technology, 141: 41-45.

-García, M. (1997). Characterization of the puri porci in comarca D'osona granges: influence of gastroenteroloy i of the consumit pins. Final career project. VIC: Escola Politècnica Superior. Universitat de Vic.

MAGRAMA-Secretary General technique (2013). Surveys livestock, analysis of the number of animals by types. www.magrama.gob.es/ca/ Ministry of agriculture, food i environment (Government of Spain).

-Pomar, j. (1984). Study of the behavior and evolution of mineral nitrogen from swine liquid manure into the soil and its availability for crops. Doctoral thesis. Lleida: Escola technique Superior D'enginyers Agronoms. Universitat Politècnica de Catalunya.

-Sana, j., Casas, C., Espona, j. Vinyeta, e. (1998). Study of the ability of purins personnel dels comarca D'osona sols d' assimilació. "Comprehensive Pla per a la Gestió dels purins comarca D'osona personnel". ASSAPORC.

-SART Medi Ambient (2013). Résultats analitics propis. Servei d' advice, research and applied technology (SART). Universitat de Vic (Vic).

-Turet, j. (1984). Aprofitament de residus agropecuaris: digestio metanogenica de residus personnel. Butll. Soc. Cat. One hundred., 2 (3): 101-108.

-Turet, j., Espona, j. Serra, x. (1992). Review dels estudis developed from the "Pla pilot per a la Gestió dels purins comarca D'osona personnel". Servei d'Assaigs i research technology (SART) of the Universitat de Vic - Consell Comarcal D'osona.

-Turet, j. i Vilalta, e. (1997). Memory of the "Pla d'estudi i Gestió dels purins personnel of Les Masies de Voltregà". Servei d'Assaigs i research technology (SART) of the Universitat de Vic - Ajuntament de Les Masies de Voltregà.

-Vilalta, e. (1993). Estudi dels efectes dels coadjuvants in the residuals d'Aigues depuració microbiologics. Final career project. VIC: Escola Universitària Politècnica D'osona. Estudis Universitaris in Vic.

-Vilalta, e., Turet, j., Costa, C. Terradellas, o. (1999). Study of the ramaderia D'osona. "Comprehensive Pla per a la Gestió dels purins comarca D'osona personnel". ASSAPORC.

-Vineyards, j. (1998). Experimental Estudi metanogenica dels purins personnel i digestio comparatiu de les seves fraccions solid liquid i. Final career project. VIC: Escola Politècnica Superior. Universitat de Vic.