Helena Nadais

Comparative valorisation of agricultural and industrial biowastes by combustion and pyrolysis

Combustion and pyrolysis processes were assessed and compared for two types of lignocellulosic biowastes: agricultural (Eucalyptus bark, grape seeds, peach stones, walnut shells, olive waste and peanut shells) and industrial (primary and biological paper mill sludge) biowastes. They were characterized by elemental, proximate and thermal analyses; the pyrolysis behaviour was studied by thermogravimetric analysis and the gases produced were identified using mass spectrometry. Agricultural biowastes showed the highest calorific values, close to the fossil fuel values (20-30MJkg(-1)) and, in general, emission of gases containing the carbon element (CH4, C2H2, CO and CO2) was higher than that of the tested industrial biowastes, making the agricultural biowastes highly competitive for combustion applications such as gas fuel. Further, the solid product which resulted from the pyrolysis of industrial biowastes is a material with large specific surface area, which is a good characteristic for possible applications as adsorbent in water remediation.

Application of Qual2Kw model as a tool for water quality management: Cértima River as a case study

Modelling can be a useful management tool because models allow the understanding of water body response to different pollution pressure scenarios which may help on the decision-making process and in prosecuting the Water Framework Directive objectives. This study aims to evaluate the usage of simple water quality models (Qual2Kw) applied to small river basins in order to better understand the response of a river to different loads of nitrogen and phosphorus. Qual2Kw model was applied to Cértima River (Portugal), a small river that ends in a shallow lake called Pateira Fermentelos and represents a very important ecosystem to the local community. Along its pathway, Cértima River has a significant enrichment in nutrients due to agriculture, livestock, domestic sewage and industrial effluents discharged into the river. In case of nitrogen, the highest loads are from domestic (44%) and diffuse (35%) sources. The main sources of phosphorous are domestic (46%), livestock (24%) and diffuse sources (20%). Cértima River is strongly enriched with nutrients, and neither nitrogen nor phosphorous is limiting the algal growth. According to the criterion of Dodds et al. (Water Res, 32(5):1455–1462, 1998), the river is classified as eutrophic. By comparing in stream measurements with Qual2Kw simulations, it can be concluded that it would be necessary to decrease the actual pollutants loads of nitrogen and phosphorous 5 and 10 times, respectively, in order to change Cértima River classification from eutrophic to mesotrophic.

A new methodology combining PCR, cloning, and sequencing of clones discriminated by RFLP for the study of microbial populations: application to an UASB reactor sample.

This work describes a methodology combining DNA extraction, polymerase chain reaction amplification with primers targeting 16S ribosomal RNA genes, cloning, and sequencing of clones previously analyzed by restriction fragment length polymorphism (RFLP), which can be applied to study the microbial diversity in a given habitat. The methodology allows the minimization of the sequencing effort, which is particularly relevant when analyzing large numbers of clones. The methodology does not require particularly skilled personnel and can easily be adaptable to the molecular characterization of virtually any particular microbial population, provided that both adequate primers and suitable restriction enzymes for RFLP analysis of the clone library have been chosen. An example of application is presented, in which a sample taken from a continuously operating upflow anaerobic sludge blanket reactor was analyzed. RFLP analysis of the initial 162 clones with HaeIII allowed the identification of only 28 distinct profiles. As expected, identical RFLP profiles corresponded to identical nucleotide sequences.

Molasses as an external carbon source for anaerobic treatment of sulphite evaporator condensate.

Failures in stability and COD removal performance often occurred in full-scale anaerobic reactors treating the evaporator condensate from a sulphite pulp mill due to substrate inhibition and occasional contaminations with red liquor (wood cooking liquor). With this work, the beneficial effect provided by the continuous addition of an external carbon source (sugarcane molasses) on the overall performance and stability of the biological process was evaluated. With a moderate addition of molasses the inhibition was mitigated which led to an increase of the COD removal rate from 52% to 77% and a methane production increase from 460 to 1650mld(-1) at an organic loading rate of 2.61g CODl(-1)d(-1). A similar conclusion can be drawn for the case when contamination with red liquor occurs. These results suggest that sugarcane molasses addition may be regarded as a low-cost operational strategy for the anaerobic treatment of sulphite evaporator condensate.

Anaerobic degradation of dairy wastewater in intermittent UASB reactors: influence of effluent recirculation

This work studied the influence of effluent recirculation upon the kinetics of anaerobic degradation of dairy wastewater in the feedless phase of intermittent upflow anaerobic sludge bed (UASB) reactors. Several laboratory-scale tests were performed with different organic loads in closed circuit UASB reactors inoculated with adapted flocculent sludge. The data obtained were used for determination of specific substrate removal rates and specific methane production rates, and adjusted to kinetic models. A high initial substrate removal was observed in all tests due to adsorption of organic matter onto the anaerobic biomass which was not accompanied by biological substrate degradation as measured by methane production. Initial methane production rate was about 45% of initial soluble and colloidal substrate removal rate. This discrepancy between methane production rate and substrate removal rate was observed mainly on the first day of all experiments and was attenuated on the second day, suggesting that the feedless period of intermittent UASB reactors treating dairy wastewater should be longer than one day. Effluent recirculation expressively raised the rate of removal of soluble and colloidal substrate and methane productivity, as compared with results for similar assays in batch reactors without recirculation. The observed bed expansion was due to the biogas production and the application of effluent recirculation led to a sludge bed contraction after all the substrates were degraded. The settleability of the anaerobic sludge improved by the introduction of effluent recirculation this effect being more pronounced for the higher loads.

Nitrogen and phosphorus discharge of animal origin in the Baixo Vouga: a spatial data analysis.

The livestock production is a strategic and crucial activity for it fixes populations in rural areas, contributing to its conservation, and most importantly because it ensures food production. By producing meat, milk or eggs, this sector contributes to national food self-sufficiency. However, intensive livestock farming activities carry a strong pollution load on the environment, particularly through the emission of nitrogen (N), phosphorus (P), and greenhouse gases (GHG). The Baixo Vouga region in Portugal due to its climatic conditions and soil characteristics holds a high number of livestock production units mainly cattle, poultry and swine. Thus such an activity contributes to a significant portion of the wealth created in this region. This high potential has collided with the existence of environmentally sensitive areas, many of which are protected by European environmental regulations. This work studies the geographical distribution of livestock population of cattle, poultry and swine in the Baixo Vouga region and quantifies its impacts on the environment by calculating the excretion loads of N and P of these species. In the cattle and poultry sectors two clusters or agglomerations are identified, the first in the northern region and the second in the inland region. Moreover, the cattle farming cluster overlaps on vulnerable zones requiring specific monitoring on effluent treatment issues.

Acidogenic Valorisation of High Strength Waste Products from Food Industry

Awareness concerning the environment and the use of clean technologies is growing worldwide. As a consequence, research on biodegradability and use of renewable resources for industrial processes has been intensive in the last years. In addition, product and process innovation in food industries is widely regarded as an essential element of competition between food companies, as it will improve their business performance. To face these new challenges, relevant changes in the food manufacturing processes may occur, involving for example the use of different raw materials as an ingredient in new food products. As a result, food processing wastewater will contain complex organic compounds with refractory properties that may compromise the biological treatment processes already existing in the wastewater treatment plants (WWTP) and consequently the fulfilment of legal requirements for wastewater discharge. To overcome this situation, segregation of specific wastewater process streams with refractory characteristics and its individual pre-treatment will be important for a viable and stable treatment in the already existing WWTP.