Konstruktivne mjere poboljšanja učinkovitosti uređaja za biološko pročišćavanje otpadnih voda

The purpose of this paper is to test of certain structural measures to improve the efficiency of the biological wastewater treatment plants by preliminary adding of oxygen to fresh wastewater and rising of the pre- treatment level. The paper compares the possibilities of increasing the oxygen content in wastewater by hydraulic jet, and by straining through a percolator with draught. The comparison is based on results obtained by testing on physical models in laboratory conditions. In both cases, several scenarios were analyzed, with different combinations of structural and hydraulic parameters (number of discharge outlets, outlet size, jet velocity and angle, size of percolator padding, etc.). Based on determined results of dissolved oxygen input (increment of dissolved oxygen concentration), the percolator was selected as the element of higher efficiency and applied on the pilot biological plant for treatment of sanitary wastewater. Based on determined efficiency of wastewater treatment during the period of two years, interpolation of the percolator as pretreatment of wastewater in biological treatment plants may be assessed as justified and useful solution.Cilj je ovoga rada ispitati određene konstruktivne mjere poboljšanja učinkovitosti uređaja za biološko pročišćavanje otpadnih voda, u smislu osiguranja prethodnog obogaćivanja svježe otpadne vode kisikom i stupnja prethodnog pročišćavanja. U radu je izvršena usporedba mogućnosti obogaćivanja otpadne vode kisikom pomoću hidrauličkog mlaza i procjeđivanjem kroz prokapnik s nategom. Usporedba se bazira na rezultatima dobivenim ispitivanjima na fizikalnim modelima u laboratorijskim uvjetima. U oba slučaja, ispitan je veći broj scenarija s različitim kombinacijama konstruktivnih i hidrauličkih parametara (broj izlijevnih mjesta, veličina izlijevnog mjesta, brzina i kut upada mlaza, veličina ispune prokapnika, visina natege). Na temelju utvrđenih rezultata unosa otopljenog kisika (prirasta koncentracije otopljenog kisika), prokapnik je odabran kao element veće učinkovitosti te je primijenjen na pilot uređaju u funkciji pročišćavanja sanitarnih otpadnih voda. Na temelju utvrđenih učinkovitosti pročišćavanja otpadne vode tijekom dvogodišnjeg perioda interpolacija prokapnika u funkciji predtretmana otpadnih voda kod bioloških uređaja može se ocijeniti opravdanim i korisnim rješenjem

Use of sludge generated at WWTP in the production of cement mortar and concrete

U radu je opisana problematika vezana uz generiranje i zbrinjavanje mulja s UPOV-a (uređaja za pročišćavanje otpadnih voda) u Hrvatskoj. Poseban osvrt je dan na mogućnost i opravdanost korištenja pepela dobivenog spaljivanjem mulja. Naglasak je stavljen na ugradnju pepela u betonskoj industriji, pri proizvodnji cementnog morta i betona. U radu su opisani rezultati dosada provedenih istraživanja u okviru svjetske prakse, s primarnim osvrtom na utjecaj ugradnje pepela na karakteristike cementnog morta i betona.Problems relating to disposal of sludge accumulating at waste-water treatment plants (WWTP) in Croatia are described in the paper. The possibility and adequacy of using ash obtained through incineration of sludge is considered. A special emphasis is placed on the significance of ash in concrete industry during production of cement mortar and concrete. Results of worldwide research conducted so far are described, with indications about the ways in which ash use influences properties of cement mortar and concrete

Determining Metal Content in Waste Printed Circuit Boards and their Electronic Components

A wide range of published scientific articles on metal content in printed circuit boards show that it is necessary to determine the content of individual metals. The aim of this paper is to show how metal content varies according to the type and age of waste electrical and electronic equipment collected in the Republic of Croatia. Samples of cell phones, TV sets, and computers are collected. The metal content is determined for electronic components and printed circuit board base plates separately for different grain sizes (1-4 mm, 0.5-1 mm, 0.1-0.5 mm and < 0.1 mm). The results show that electronic components form a larger part of printed circuit board mass fraction depending on the equipment age and type. Generally, electronic components do have a higher mass fraction for most metals (like: aluminium, copper, nickel, zinc, gold, and silver in most cases) in comparison to printed circuit board base plates, but for certain metals (like: lead, tin) the opposite applies. The electronic components of larger grain sizes (1-4 mm and 0.5-1 mm) contain more aluminium, copper, and zinc, and less lead, while the smaller grain size fractions are richer in gold. The bare boards base plates of larger grain sizes contain more copper, lead and tin, while the smallest grain size class (< 0.1 mm) contains more aluminium and gold. No clear trends are noticed in the case of silver and lead

COMPOSTING OF FINE FRACTION AFTER MECHANICAL-BIOLOGICAL TREATMENT OF MUNICIPAL SOLID WASTE

One of most common types of municipal solid waste treatment is mechanical-biological treatment (MBT), which in practice has many variations depending on the method of conducting the technological process and it is possible to get different output fractions. In this paper is analysed waste generated after the MBT with biodrying, where waste after mechanical treatment undergoes process of biodrying, and then is RDF (recovery derived fuel) separated. Fine fraction remains with a high content of organic matter that without additional processing cannot be disposed of on a landfill. The aim of this research was to determine the possibility of fine fraction composting in different conditions – in the open, in the open and covered area, and indoors. In each area are formed three compost piles: 100% fine fraction (KH1, KH4, and KH7), 70% fine fraction and 30% wood chips (KH2, KH5, and KH8), 50% fine fraction and 50% wood chips (KH3, KH6, and KH9). Moisture content, temperature and dissolved organic carbon (DOC) were monitored. Results show that after 13 weeks samples KH1, KH4, and KH7 (100% content of fine fractions) did not achieve DOC value less than 3 000 mg/l. The most effective composting in terms of reducing the DOC is achieved in samples KH3, KH6, KH9. Based on results obtained, it can be concluded that by adding wood chips in fine fraction in ratio 50:50, the most effective and fastest reduction of organic matter is achieved in the analysed samples

CHALLENGES AND POSSIBILITIES FOR ENVIRONMENTALLY SOUND RECYCLING OF SHIPS AND COMPOSITE BOATS IN EUROPEAN UNION

In this paper are presented challenges that countries of European Union face when recycling ships and composite boats. European ship owners control over 40 % of the world’s merchant ship fleet, with Greece as the top ship-owning country globally. Nowadays, ship recycling is being regulated and positive progression was made towards it since steel industry belongs in world’s top five and stable market and makes recycling of scrap metals from ships attractive. On the other hand, yachts, sailing boats and small boats are mainly made from composite materials because of their favourable properties, making them great investment, but end-of-life management is more complicated and not quite regulated by the law yet. Unlike commercially oriented ships, which are constantly in move and disposed when the maintenance costs of the vessel start to exceed possible revenue, old boats for recreational and tourism-oriented purposes most rarely move. Hundreds of thousands lie in marinas and are abandoned due to the maintenance costs thus discouraging the owners from keeping it. Hence, a growing number of marinas worldwide will have the problem of boat disposal in a sustainable way in the future. In this paper is given short summary on waste ships and boats management issues. The emphasis is on waste management of small composite boats

The Possibility for Environmental Friendly Recycling of Printed Circuit Boards

The goal of this work is to find a solution for disposal of Vitroplast FR4, a material found in waste printed circuit boards. In this study, the influence of addition of Vitroplast, generated by mechanical treatment of printed circuit boards waste on concrete properties such as compressive strength was investigated in laboratory conditions. By substitution of filler (i.e. sand) in a mass ratio of 5, 10, 15 and 20% with Vitroplast in concrete mixture, the compressive strength decreased into 57.5, 84.5, 95.0 and 95.9%. The results of leaching tests have shown that by incorporating Vitroplast in concrete mixtures in a 10% mass ratio, the elution of arsenic and cadmium is below the limitations prescribed for inert wastes. The studied approach offers the possibility for environmental friendly recycling of printed circuit boards

Konstruktivne mjere poboljšanja učinkovitosti uređaja za biološko pročišćavanje otpadnih voda

The purpose of this paper is to test of certain structural measures to improve the efficiency of the biological wastewater treatment plants by preliminary adding of oxygen to fresh wastewater and rising of the pre- treatment level. The paper compares the possibilities of increasing the oxygen content in wastewater by hydraulic jet, and by straining through a percolator with draught. The comparison is based on results obtained by testing on physical models in laboratory conditions. In both cases, several scenarios were analyzed, with different combinations of structural and hydraulic parameters (number of discharge outlets, outlet size, jet velocity and angle, size of percolator padding, etc.). Based on determined results of dissolved oxygen input (increment of dissolved oxygen concentration), the percolator was selected as the element of higher efficiency and applied on the pilot biological plant for treatment of sanitary wastewater. Based on determined efficiency of wastewater treatment during the period of two years, interpolation of the percolator as pretreatment of wastewater in biological treatment plants may be assessed as justified and useful solution.Cilj je ovoga rada ispitati određene konstruktivne mjere poboljšanja učinkovitosti uređaja za biološko pročišćavanje otpadnih voda, u smislu osiguranja prethodnog obogaćivanja svježe otpadne vode kisikom i stupnja prethodnog pročišćavanja. U radu je izvršena usporedba mogućnosti obogaćivanja otpadne vode kisikom pomoću hidrauličkog mlaza i procjeđivanjem kroz prokapnik s nategom. Usporedba se bazira na rezultatima dobivenim ispitivanjima na fizikalnim modelima u laboratorijskim uvjetima. U oba slučaja, ispitan je veći broj scenarija s različitim kombinacijama konstruktivnih i hidrauličkih parametara (broj izlijevnih mjesta, veličina izlijevnog mjesta, brzina i kut upada mlaza, veličina ispune prokapnika, visina natege). Na temelju utvrđenih rezultata unosa otopljenog kisika (prirasta koncentracije otopljenog kisika), prokapnik je odabran kao element veće učinkovitosti te je primijenjen na pilot uređaju u funkciji pročišćavanja sanitarnih otpadnih voda. Na temelju utvrđenih učinkovitosti pročišćavanja otpadne vode tijekom dvogodišnjeg perioda interpolacija prokapnika u funkciji predtretmana otpadnih voda kod bioloških uređaja može se ocijeniti opravdanim i korisnim rješenjem

Use of incinerated sewage sludge ash in cement mortars: case study in Croatia

U ovom radu je provedeno istraživanje mogućnosti i opravdanosti uporabe mulja s uređaja za pročišćavanje otpadnih voda na način da se pepeo dobiven spaljivanjem mulja ugrađuje u cementni mort kao sirovina (zamjena dijela cementa). U radu su provedena ispitivanja na cementnom mortu, pri čemu su razmatrane usporedbe osnovnih svojstava mješavina morta bez dodatka pepela i s dodatkom određenih udjela pepela dobivenog spaljivanjem mulja na temperaturi 800 °C. Dodatno je ispitivan i utjecaj dodatka aditiva (metakaolina i silicijske prašine), s ciljem poboljšanja fizikalnih karakteristika morta. Ukupno je proizvedeno i ispitano 177 uzoraka cementnog morta s 9 različitih mješavina. Za potrebe ovog istraživanja rabljen je mulj dobiven na uređaju za pročišćavanje otpadnih voda u Zagrebu. Dobiveni rezultati s dodatkom pepela pokazali su zadovoljavajuća svojstva što navodi na zaključak da je u pogledu ispitivanih svojstava (obradljivost, vrijeme vezivanja, čvrstoća na savijanje i tlačna čvrstoća) moguća i opravdana uporaba mulja u proizvodnji cementnog morta.In the paper an experimental research has been carried out regarding the possibility for the use of incinerated sewage sludge ash (ISSA) in the production of cement mortars with partial cement replacement. Different mixtures of cement mortar have been investigated, with comparison of its basic characteristics with and without certain amounts of added ISSA that was incinerated at the temperature of 800 °C. Additionally, the influence of the additives (metakaolin and silicon dust) was also investigated with the purpose to improve the physical characteristics of mortars. Altogether 177 specimens of cement mortar were investigated, with 9 different mixtures. In this research the sewage sludge from the Zagreb wastewater treatment plant was used. Results have shown satisfying physical and mechanical characteristics of mortars with added ISSA (workability, setting time, flexural and compressive strength) which brings to conclusion that use of ISSA in production of cement mortars seems possible and justified

Greenhouse gases reduction through waste management in Croatia

The climate change policy is one of the key factors in the achievement of sustainable development in the Republic of Croatia. Control and mitigation of green house gases is correlated with all economy activities. Waste management is one of the main tasks of environmental protection in Croatia. The Waste Management Strategy of the Republic of Croatia and the Waste Management Plan in the Republic of Croatia define the concept of waste management hierarchy and direct and indirect measures as criteria for sustainable waste management establishment. The main constituent of this system is avoiding and minimizing waste, as well as increasing the recycling and recovery level of waste and land fill gas, which also represent green house gases mitigation measures. The Waste Management Plan consists of several direct and indirect measures for green house gases emission reduction and their implementation also affects the green house gases emissions. The contribution of the methane emission from land fills amounts to about 2% of the total green house gases emissions in Croatia. The climate change control and mitigation measures as an integral part of waste management sector strategies represent the measures of achieving the national objectives to wards green house gases emission reduction which Croatia has accepted in the frame work of the Kyoto Protocol