Neural networks and their application in water management

U radu su detaljnije opisane neuralne mreže koje su dnaas sve češće u primjeni pri rješavanju problema iznimno visokog stupnja složenosti. Uz definiranje neuralnih mreža, dana je njihova podjela, prikaz strukture i osobina te je izdvojen pregled povijesnog razvoja. Istaknuta je primjenu neuralnih mreža unutar područja vodnog gospodarstva i to prije svega na području Hrvatske. Pri tome su ukratko opisane najznačajnije neuralne mreže koje su do danas razvijene i rabljene u praksi.Neural networks, nowadays increasingly used for solving problems of exceptionally high level of complexity, are described in great detail. After definition of neural networks, their classification is given, and their structure and properties are presented. An overview of their historic development is also given. An emphasis is placed on the use of neural networks in water management, especially in the territory of Croatia. At that, most significant neural networks developed so far and used in current practice are briefly presented

TREATMENT OF WASTEWATER FROM SEPARATORS FOR RAINFALL RUNOFF USING ELECTROCHEMICAL OXIDATION PROCESSES

In recent years, industry has increased and with it the amount of oily wastewater, which are considered hazardous waste because they contain various types of heavy metals and oils that endanger the environment and human health. In the last twenty years, there has been increased research on new technologies to treat wastewater as efficiently and environmentally friendly as possible. A recent approach to wastewater treatment is the application of electrochemical processes such as the electro-Fenton process, which belongs to the group of electrochemical advanced oxidation processes and electrocoagulation. The aim of this work was to remove organic contaminants and heavy metals from wastewater originating from oil and grease separators that clean stormwater runoff from traffic areas. The use of stainless steel, iron and aluminum electrodes results in electrooxidation, electroreduction and electrocoagulation. At a current of 15 A the treatment efficiency was 50% for COD and 73% for mineral oil. At a current of 110 A the treatment efficiency was 96% for COD and 90% for mineral oil

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

Analysis of Sewage Sludge Disposal Routes – Varazdin and Medimurje County

The aim of this paper is to analyse sewage sludge production at the level of Medimurje and Varazdin counties with economic analysis of acceptable technical/technological solutions for sludge management routes. The topic is very broad, so the focus was placed on four variants of sludge disposal, which were determined by preliminary analysis to be the most applicable for the area in question. These are: 1) disposal of sewage sludge in agriculture, 2) incineration of sludge in a central mono-incinerator, 3) composting for the area of Varazdin County and at the same time use of sludge reed beds for the area of Medimurje County, and 4) export of sludge outside the state borders. Based on the analysis carried out for the described four variants, sludge incineration in a regional mono-incinerator turned out as the economically most advantageous solution, while the variant that includes disposal of sludge in agriculture has showed as the most expensive one. The last one also showed the largest range of costs uncertainties, but the mentioned facts are greatly influenced by unfavourable legislation, the changes of which in a more rational direction would greatly contribute to the greater competitiveness of this variant. Overall, taking into account the lowest cost and uncertainties in the predicted unit costs, the sludge composting in the Varazdin County and the construction of a reed beds for the Medimurje County, turned out to be the optimal variant. This solution is also the one that was ultimately adopted in practice

Application of Byelaw on fire fighting hydrant network in rural areas

Zastupa se mišljenje da je u vodoopskrbi ruralnih područja moguće razdvojiti vodoopskrbu stanovništva od gašenja požara, tako da se vodoopskrbi stanovništva da prioritet, jer se zaštita od požara može riješiti alternativno uz ista ili manja sredstva. To je ekonomski važno. Za ilustraciju razlike u investiciji, pri primjeni ili ne Pravilnika o hidrantskoj mreži za gašenje požara, analiziran je na razini idejnog projekta konkretan primjer vodoopskrbe visoke zone općine Desinić.The authors consider that water supply for population can be separated from fire fighting in the organization of water supply for rural areas. This can be done by giving priority to water supply for population, as fire protection can be solved alternatively, using similar or lesser funding. This is significant from the economic standpoint. A concrete example of water supply in the elevated area of Desinić Municipality is analyzed at the preliminary design level, in order to illustrate the difference in investment in case of application or non-application of the Byelaw on the Fire Fighting Hydrant Network

Manhole spacing along sewerage network

Predložene su izmjene postojeće prakse u određivanju najvećeg razmaka kontrolnih okana na ravnim potezima kanala istog poprečnog presjeka, koja je nasljeđe tehnološkog stanja razvoja postupaka održavanja kanalske mreže iz prve polovice prošlog stoljeća. Prikazane su i obrazložene mogućnosti novih tehnologija održavanja koje omogućavaju bitno veće minimalne razmake. Uštede su moguće na svim sustavima javne odvodnje, a naročito u području odvodnje oborinskih voda s prometnica.The authors propose a change in current practice relating to maximum spacing among manholes on straight sections of ducts of similar cross section. This spacing is a remnant of sewerage system maintenance practices that have been in use since the first half of the past century. Advantages of novel maintenance technologies, enabling adoption of much greater minimum distances among manholes, are presented and explained. Considerable savings can thus be made on all public drainage systems, and especially in the sphere of rainwater drainage from roadways

Comparison of different methods for expressing water losses with a review of their practical implementation in Croatia

U današnje se vrijeme u svijetu koriste različiti načini iskazivanja vodnih gubitaka u vodoopskrbnim sustavima. Najčešće je iskazivanje postotnog udjela u odnosu na zahvaćene količine, zatim izračun stvarnih i prividnih gubitaka u sklopu standardne bilance vode i izračun ILI (eng. Infrastructure Leackage Indeks; hrv. Infrastrukturni indeks curenja) pokazatelja sukladno IWA (eng. International Water Association) metodologiji. ILI pokazatelj predstavlja odnos stvarnih i neizbježnih količina vodnih gubitaka na razini jedne godine. U radu je dan kritički osvrt na pouzdanost ILI pokazatelja pri analizi vodnih gubitaka. Na konkretnim primjerima je dokazano da na temelju ILI pokazatelja nije pouzdano donositi konkretne zaključke o stanju vodnih gubitaka, kao i o definiranju mjera unaprjeđenja cjelovitih sustava ili pojedinih DMA zona (eng. District Metering Area; hrv. Izdvojena mjerena zona). U analizi vodnih gubitaka se osim izračuna ILI pokazatelja koriste i različiti načini iskazivanja i vrednovanja vodnih gubitaka (l/(priključak∙dan), m3/(km cjevovoda∙dan), l/(priključak∙dan∙mVS), m3/(km cjevovoda∙dan∙mVS), HRK/godina i dr.). S ciljem iznalaženja što jednostavnijeg i pouzdanijeg načina iskazivanja vodnih gubitaka, u ovom su radu, na konkretnih pet primjera vodoopskrbnih sustava u Hrvatskoj, analizirani odnosi različitih načina iskazivanja vodnih gubitaka. Zaključuje se da je najpraktičnije i najučinkovitije provođenje ekonomskih analiza vodnih gubitaka s izražavanjem vodnih gubitaka u HRK/godina, kako za sustav u cjelini, tako i za svaku DMA zonu posebno.There are different methods for expressing water losses in water supply systems, which are presently used in the world. Water losses are most frequently expressed as a percentage of abstracted water quantity, a calculation of real and apparent losses as part of the standard water balance and calculation of the Infrastructure Leakage Index (ILI) according to the International Water Association (IWA) methodology. The ILI presents the relation between the real and unavoidable annual water losses. The paper offers a critical review of the reliability of the ILI in the analysis of water losses. By using specific examples, the paper proves that it is not reliable to draw concrete conclusions about the state of water losses or to define measures for improving integrated systems or individual district metering areas (DMAs) based on the ILI. In addition to the ILI calculation, numerous other methods of expressing and assessing water losses are also used, such as l/(connection per day), m3/(km pipeline per day), l/(connection per day mWC), m3/(km pipeline per day mWC), HRK/year, etc. In order to find the simplest and most reliable method for expressing water losses, this paper analyses relations between different methods for expressing water losses on five specific water supply systems in Croatia. It has been concluded that the most practical and efficient performance of economic analyses of water losses is when water losses are expressed in HRK/year, both for the system as a whole and separately for each individual DMA