Olita Medne

Sustainable Utilization of Sewage Sludge: Review of Technologies

Biological treatment of municipal and industrial wastewater becomes more common in EU countries. As a result, the amount of wastewater sludge increases. The political and economic situation in world is requiring new methods for recovery of non-renewable mineral resources. Sludge is great secondary source of many elements. The aim of this research is to summarize available techniques for sustainable utilization of industrial sludge and recovery of critical raw minerals (CRMs). The most common sustainable method is using treated sludge as fertilizer in agriculture due to high content of P, N, C and microelements. However, this method has many restrictions, e.g. it can contain toxic substances or lack of appropriate land. Thermal sludge treatment methods like pyrolysis have developed crucially in last decade and pyrolysis units for sludge treatment are commercially available now. Pyrolysis becomes the most sustainable method due to recovery of CRMs and better energy recovery comparing to incineration.

ANALYSES OF THE CAUSE AND EFFECT DIAGRAMMS OF EXPANDED POLYSTYRENE MANUFACTURING PROCESS

The manufacturing of expanded polystyrene is a multi-stage process. In each stage the number of technologic parameters is very high, they are intercorrelated and influence the quality of the end product. The improper combination of parameter quantitative values causes defects – deterioration of mechanical and heat insulation properties, product deformation and cracking. The planning of experiments for parameter discrimination and afterwards optimization is not practicable due to the high number of variables. That is why we used the cause and effect diagrams for the identification of the most essential parameters. After analyzing the regulation of the technological process a cause and effect diagram (the so-called”fish-bone”) was created for each stage. Further on, after having analyzed the literature data and using the experience gained in the real manufacturing process, the set of eventually most essential parameters was defined. Also the number of these parameters is quite high, however it already gives a possibility to perform purposeful experiments and make an analysis of the experimental results.

Investigation of Daily Covering Material for Biocells

Abstract Bioreactor landfilling, with the acceptance of landfill Directive 1999/31/EC has lost its actuality in European Union; at the same time, this method can still be used for acceleration of biowaste degradation and biogas production. One of the possibilities to reduce the disposal of biowaste is to use biocells for its anaerobic pre-treatment before landfilling. The daily filling up of such a cell requires isolation of the main volume to limit gas emissions, reduce smells, etc. Bioprocesses that are of the utmost importance for biocell treatment are often not taken into account in selection of materials to be used as daily landfill covers. Based on physical, chemical and biological methods the investigations have been carried out into different covering materials offered in the market, with identification of parameters that are the most important for daily covering the biocells. It is found that the materials fitted best this purpose should be of biological origin and consist of small bio-particles with large surface, without the inhibitors of anaerobic processes such as sulphuric compounds. Kopsavilkums Bioreaktoru pielietošana atkritumu uzglabāšanas sfērā, sakarā ar Direktīvas 1999/31/EC pieņemšanu, ir zaudējusi savu aktualitāti, taču šī metode vēl joprojām var tikt izmantota bioatkritumu noārdīšanai un biogāzes ražošanai. Viena no iespējām kā samazināt bioatkritumu izvietošanu ir biošūnu izmantošana bioatkritumu anaerobai pirmsapstrādei pirms to noglabāšanas. Šūnas piepildīšana ikdienā prasa nepieciešamību izolēt lielāko tās daļu, lai samazinātu gāzes emisiju, smakas, utt. Materiāli, kas ikdienā tiek izmantoti atkritumu pārklāšanai, nepietiekami ietekmē bioprocesus, kas pamatā ir galvenais biošūnas izmantošanas mērķis. Šajā sakarā ir veikta dažādu tirdzniecībā pieejamu pārklājuma materiālu izpēte, pielietojot virkni fizikālo, ķīmisko un bioloģisko metožu, un nosakot svarīgākos parametrus, kas ir būtiski šo materiālu izmantošanai ikdienā kā biošūnas pārklājumu. Pētījumu rezultātā noteikts, ka visatbilstošākie ir materiāli ar bioloģisko izcelsmi, sastāvoši no mazām bio daļiņām ar lielu laukumu bez anaerobo procesu inhibitoriem, piemēram, sēra komponentēm.