Pollution of atmosphere and decrease of fossil fuels stimulates people to search for an alternative energy sources for production of energy, both electrical and heat. In Latvia it is possible to use almost all alternative energy sources for production of energy, including solar energy that becomes more relevant year by year. Solar radiation in direct way makes no hazardous, but, as the intensity of solar radiation in geographical location of Latvia is comparatively low, the utilization of it demands relatively expensive equipment. Production of energy from other sources of energy also demands certain investments as well as the purchase of fuel, maintenance of equipment and presence of different manipulators. In practice several types of solar collector constructions with efficiency from 30 up to 75% exist and expenses vary in the wide range. The average number of sunshine hours in Latvia is about 1800 hours yearly. Nevertheless solar collectors for water heating in Latvia are used. Mostly flat-plate collectors are used whose efficiency often is not sufficient and water has to be additionally warmed-up. The aim of our investigation is to study operation of evacuated tube collector in conditions characteristic to Latvia. It is stated that it is feasible to use evacuated tube collector for water heating in Latvia, especially from March till October. During winter period solar collector can be used as additional energy source for water heating.

The pollution of the river water with organic matter deteriorates the chemical, biological and microbiological quality of the water and has a negative effect upon the biological variety of the water environment. The paper analyses the study period (1996-2000) seasonal change of organic matter in the upper reaches of the River Nevezis (study sites upstream and downstream Panevezys). The highest amount of organic matter (according to chemical oxygen demand and biochemical oxygen demand) got into the river under the influence of concentrated pollution, the fewer amount - under the influence of agricultural pollution and in the course of natural processes. The concentration of organic substances in the river water had a seasonal character: rivers with a better ecological state (the Juosta) were more polluted with organic matter in spring, when water temperature was below 10 deg C, but rivers with a worse ecological state (the Nevezis upstream and downstream Panevezys) – in summer (water temperature was higher than 10 deg C). This may be related with fresh pollution; in the former case organic matter might have come from the environment together with the runoff, in the latter case - due to decomposition of water vegetation and fauna residues in the river itself. In all rivers water temperature was by 0.1-4.4 deg C higher in 1996-2000 in comparison to that in 1986-1989, a significant temperature increases were observed in winter and autumn. The water temperature arose mostly below the town.

As worldwide trends are changing gradually and sustainable resources economy and reduction of hazardous emissions are coming to the forefront, several industry sectors are forced to revalue their resource consumption. The main emphasis is currently placed on the recycling of by-products. One of the methods, definitely, includes burning of by-products to generate power, however it is not always the most efficient one. By-products must be used in the manner that ensures that they provide high added value for the operation of the company and are environmentally friendly. This research focuses on the use of the by-products of birch (Betula) veneer manufacturing, in order to obtain thermal insulation material. The following characteristics of the wood fibre insulation material were determined: thermal conductivity, water absorption, vapour permeability, and prototype reaction to fire. The characteristics of the obtained wood fibre thermal insulation material: thermal conductivity 0.038 W•mE-1•kE-1; water absorption 12 kg•mE-2; the conformity of the material even to D fire reaction class was not determined. The principal conclusion: the wood fibre thermal insulation material conforms to the requirements set for thermal insulation materials.

The properties of the transverse section surface of the wood are crucial when using it as an adhesive in finger joints. Contact angles of three test liquids sessile drops - water, diiodomethane and ethylene glycol - with known characteristics of surface free energy were measured on wood surface with the grain orientation 45 ° against the plane. Acid–base approach was used to calculate surface free energy and its characteristics of Scots pine (Pinus sylvestris L.) with moisture content of 21% and Norway spruce (Picea abies L. Karst) with moisture content of 10% wood samples from values of the contact angle. The wetting behavior of the wood samples was examined with the contact angle method (goniometer technique) in the Laboratory of the Department of Chemistry of Latvia University of Agriculture at the beginning of 2013. The aim of this study was to verify possibility of determining the contact angle values of the wood and calculate the surface free energy and its components of wood from the obtained contact angle values using acid-base theory. At the end of this study it was concluded that the acid–base approach is a suitable method to calculate surface free energy and its characteristics of wood from the values of the contact angle. Nevertheless, indirect methods of liquid drop contact angle value estimation must be used because direct determination is not feasible on wood surfaces with open capillaries.

Plywood overlaid with resin impregnated paper films is used in various decorative applications for which high stability of aesthetic qualities is of great importance. The top veneer of the plywood for these materials is perfectly protected from a direct contact with water as far as the covering film is not damaged. However, in case of film damage water can cause clearly visible defects in a relatively short period of time. To reduce these types of defects, unsophisticated and efficient way was developed. It involves filling the vessel system of the top veneer with industrial phenol-formaldehyde resin by using a hot-press. Influence of some phenol-formaldehyde resin properties on its penetration in birch veneer as well as the effect of wood moisture content were tested. The proposed top veneer pre-treatment method with phenol-formaldehyde resin reduced the average swelling zone distance from damage site by half for oven pre-dried plywood with 3% moisture content before treatment. Moreover, it was found that using plywood with moisture content of 9% the swelling zone distance was reduced by two thirds compared to untreated overlaid plywood.

Currently public services become more and more significant in procurement of daily activities of each inhabitant and the entire society. Therefore optimal solutions of the regulatory issues are the topic of the day. Objective of the article is to analyse regulatory systems of the provision of water and waste water utilities in Latvia and in other countries, to draw conclusions derived from the analyses and put forward suggestions for the choice of the most appropriate regulatory system in the local governments of Latvia. The hypotheses advanced in the study have proved that each country may use its own discretion when selecting the regulatory system for water and waste water utilities.