Aleksandar Đukić

This paper assesses the operational performance of drainage systems on four road bridges over the Sava River in Belgrade: Branko’s, Gazela, Ada Ciganlija, and Ostružnica. Field inspections identified deficiencies related to original design, subsequent modifications, ageing drainage infrastructure, structural and pavement deformations, and inadequate maintenance, all of which can significantly reduce drainage effectiveness. Particular attention is given to the Gazela Bridge, where hydraulic analysis showed that an average structural deflection of 14 cm reduces flow velocities in drainage pipes by about 10% for the 10-year design storm, increasing the potential for sediment deposition and pipe blockage. The four cases demonstrate that drainage functionality can be compromised at different stages of the bridge life cycle. The paper highlights the need for continuous inspection of structural and drainage components and performance-based maintenance.

Definitions of Non-Revenue Water (NRW), the Economic Level of Leakage (ELL), and their components are well-established and extensively documented in the literature. However, their practical calculation is often complex, typically requiring data that may not be readily available, or which must be estimated. In particular, the methodology used to determine the ELL is frequently subject to debate. All water supply systems (WSS) seek to minimize water losses, but the key challenge lies in identifying the optimal level of loss reduction. Beyond purely financial considerations, leakage reduction activities can have significant operational, social, and environmental implications for WSS. The broader environmental context in which a WSS operates can also shape the acceptable level of NRW. In this paper, the Acceptable Leakage Level (ALL) is defined as the level of NRW that is considered acceptable for a given WSS within its societal context, but is not universally quantifiable. The ALL can differ from the ELL, and this paper presents examples from Serbia and other countries. Factors influencing ALL are also discussed, including the underlying reasons for its divergence from ELL.

The study analyzes the water quality status within the "Duboko" Regional Sanitary Landfill Complex. The investigations indicated that landfill leachate is potentially the most significant source of environmental pollution. Landfill leachate must therefore be efficiently collected and treated prior to discharge. Based on the investigations conducted in 2025, other available data, and previous studies, conclusions and recommendations are presented concerning water quality and potential treatment technologies. These technologies may involve a combination of biological and physicochemical processes, including membrane separation processes, capable of ensuring a high quality of treated effluent that complies with the applicable emission limit values and does not compromise the required quality of the receiving water body (Class II).

Sistemi za vodosnabdevanje, odvođenje i prečišćavanje otpadnih voda osnovni su preduslovi održivog razvoja i zaštite javnog zdravlja. Tokom višedecenijskog i viševekovnog razvoja, ovi urbani sistemi postali su sve kompleksniji i obimniji, čime je ocena njihovog stanja i pouzdanosti rada postala sve zahtevniji inženjerski zadatak. U radu su detaljnije prikazani makro i mikro pristupi u oceni stanja komunalnih hidrotehničkih sistema. Makro pristup obuhvata identifikaciju ključnih pokazatelja funkcionisanja sistema na nivou dela naselja, celog naselja, regiona ili države, dok mikro pristup omogućava prepoznavanje konkretnih uzroka uočenih problema, kao i definisanje lokacija i obima neophodnih rekonstrukcija i intervencija. Za sveobuhvatnu i efikasnu procenu sistema vodosnabdevanja i kanalizacije neophodna je integrisana primena oba nivoa analize. Posebna pažnja biće posvećena aktuelnim trendovima u ovoj oblasti, sa naglaskom na digitalizaciju i uvođenje naprednih informacionih tehnologija u upravljanje komunalnim hidrotehničkim sistemima.

U radu je analizirano je stanje kvaliteta životne sredine u okviru kompleksa regionalne sanitarne deponije „Duboko“. Prema izvedenim istraživanjima 2025. godine, drugim dostupnim podacima i ranijim ispitivanjima, dati su zaključci i preporuke u vezi sanacije i rehabilitacije deponije. Ispitivanja su ukazala da su procedne otpadne vode deponije potencijalno najveći izvor ugrožavanja životne sredine. Procedne vode deponije moraju na efikasan način biti sakupljene i prečišćene pre ispuštanja, kombinacijom bioloških i fizičko-hemijskih postupaka, uključujući i procese membranske separacije, koji će garantovati visok kvalitet prečišćene vode koji neće ugroziti zahtevani kvalitet recipijenta (II klasa).

The inflow of infiltration and rainwater into the foul sewers cannot be completely avoided, but if this inflow is excessive, it can lead to serious consequences for the operation of sewerage and municipal wastewater treatment plants. The paper presents the causes and consequences of clean water inflow into the sewage, with an emphasis on their impact on the sewer system performance and the efficiency of municipal wastewater treatment processes. In the context of accelerated construction of sewage systems and treatment plants, it is highlighted that urgent and systematic attention must be paid to this issue in the Republic of Serbia.

Urban areas are increasingly challenged by pluvial flooding, driven by climate change and the expansion of impervious surfaces. Conventional sewer systems often lack the capacity to manage increased volumes of stormwater, resulting in water spills in the lowest floors of buildings, retention of water on the ground and potential contamination. Implementing nature-based solutions, such as porous concrete pavements, supports controlled infiltration and retention of stormwater, thereby reducing peak flows, lowering runoff volumes, and improving infrastructure durability. The integration of nature-inspired solutions and gray infrastructure leads to an increased use of recycled materials for the sustainability and resilience of urban environments to flooding.

The paper presents the causes and consequences of clean water inflow into the sewage system, with a particular focus on its impact on the functioning of the sewer network and the efficiency of the wastewater treatment process. Special emphasis is placed on the urgent need for a systematic and adequate response to this issue in the Republic of Serbia.

The paper presents an analysis of water losses from 42 waterworks in the Republic of Serbia using the ILI indicator and expressing losses as a percentage of input system volume. The analysis was performed using available data, with missing data being adopted by assessing operating conditions. The analysis clearly indicated the advantages of using the ILI indicator, which takes into account the local specificities of the configuration and operation of the waterworks system. Paper points out the risk of using data on water losses expressed as a percentage of system input volume, and in particular of arbitrarily prescribing a target percentage of water losses, without analyzing the state and characteristics of a specific waterworks system, as this approach can lead to setting unrealistic and unachievable goals. A preliminary methodological framework for defining targeted water losses in Serbia is presented as well as the need for further research and improvement of the reliability of data on distribution water systems in order to increase the reliability of water loss estimates and realistically set water loss reduction goals.

The paper presents challenges that urban drainage has to solve under altering hydrological regime due to urbanization. The need for reducing the negative impacts of urbanization on the quantity and quality of urban runoff is emphasized. Innovative methods of urban drainage have been presented, together with general recommendations for their application. The requirements from the proposal of the new EU Directive on urban wastewater related to the integrated management of urban wastewater, including rainwater, are presented in more detail.