Simulation models (Epanet, Piccolo, Mike Net, WaterCad) are common analytical tools employed to evaluate various operational scenarios of water supply systems. Their use includes estimating hydraulic conditions for variable water demand in water pipe networks. Hydraulic models are also used to design changes in water quality, the scope of which largely depends on hydraulic conditions of water supplies. The paper presents the simulation results of free residual chlorine decay according to three operational scenarios for the water supply system, including minimum, medium, and maximum water demand from year 2017. The results were used to build a statistical model of free residual chlorine concentration changes in water, considering the distance from the disinfectant dosing point, water flow velocity, and bulk chlorine decay rate. According to the constructed model, hydraulic conditions had a major impact on quality of the supplied water, while the free residual chlorine decay factor proved less significant. Favorable conditions with respect to tap water quality were noted for the water flow velocity above 0.5 m/s.
The paper discusses the origins and tradition of disinfection process application in water treatment systems paying special attention to its complexity and methodological problems. Disinfection was presented as the main objective of water treatment technology that guarantees safe microbiological water quality. A new approach to the process of disinfection was proposed as a result of the expansion of its functions and objectives as a foundation for drinking water quality safety. It was demonstrated that disinfection should become an integral part of the whole water supply system, comprising both water treatment technology and distribution system. Such an approach results from the position of disinfection process in the system, as an indirect link between the technological system and distribution network. The concept also assumes use of disinfection to monitor and diagnose safety of the water supply system as a whole. Attention was also paid to the research tasks accompanying design and operation of the disinfection process in combination with a reliable evaluation of biological water stability in water networks. The article presents the analysis of methodological criteria of the disinfection process affecting chemical oxidant and dose selection, contact time, dosing site location as well as by-product identification and reduction in their formation.
The paper presents the results of investigations of local resistance coefficients (zeta) in welded polypropylene (PP) elbows of 0.02 m in diameter, angled at 90 degrees. The investigations were performed on the purpose-built laboratory measurement stand. The scope of the research encompassed the elbows which were: properly warmed up and properly pressed (welded at the proper temperature and pressed with proper force onto the pipe); insufficiently warmed up and insufficiently pressed (welded at too low temperature and pressed with too low force onto the pipe); excessively warmed up and excessively pressed (welded at too high temperature and pressed with too high force onto the pipe). The local resistance coefficients zeta determined in measurements according to the PN-EN 1267 standard were compared to those calculated in accordance with the PN-76/M-34034 standard. The average value of the local resistance coefficient zeta, determined in measurements for properly welded and properly pressed elbows, was zeta(1p) = 0.806, for insufficiently warmed up and insufficiently pressed elbows - zeta(2p) = 1.341 and for excessively warmed up and excessively pressed elbows - zeta(3p) = 2.941, whereas only zeta(4) = 0.157 was obtained from calculations according to PN-76/M-34034 standard. It was demonstrated that the local resistance coefficient values calculated for the welded PP elbows as per the PN-76/M-34034 standard were underestimated when compared with the ones experimentally measured. Based on these values, the formulas for the project purposes and in accordance with the PN-92/B-01706 standard were proposed to develop a nomogram for local resistance coefficient zeta determination in function of water flow velocity in DN 20 PP elbows. The results justified a need to develop precise calculation techniques and a new standard for local resistance coefficient determinations. As the real value of local resistance coefficients zeta in welded polypropylene elbows strongly depends on the welding time and pressing force, it is necessary for pipe fittings manufacturers to precisely determine the welding time and pressing forces as well as to equip the welding sets with dynamometers to measure the pressing force during the welding process.
The amended Water Law Act together with the "Program of measures aimed at reducing the pollution of waters with nitrates from agricultural sources and prevention of further pollution" was adopted in August 2018. The new regulations completely changed the implementation of the Nitrates Directive, recognizing the whole country as one large area of NVZ (nitrate vulnerable zone). In addition, "pole of cold" and "pole of heat" areas were designated where fertilization time-lines were shortened or extended accordingly. It is too early to confirm the efficiency of the new regulations based on monitoring data or quantify their contribution to limiting nitrogen load in surface waters. Therefore, in this article, a DNS/SWAT macromodel was employed as a prognostic tool to develop three variant scenarios simulating the effects of limitation or extension of fertilization periods in the exemplary catchment of Przymorze (Slupia river, Charnowo profile). The results obtained allowed for a precise determination of both the total nitrogen load in the selected calculation profile and the anticipated degree of its reduction or increase depending on the assumed length of the fertilization period. The results indicate that more restrictive regulations regarding fertilization periods translate into a reduction in total nitrogen load in surface waters. Recently developed tools such as Polish Atlas of Rainfall Intensity (PANDa rainfall model) may significantly improve validation of the models employed. In these models, the meteorological module plays a central role like in the DNS/SWAT macromodel equipped to perform water quality analyses with a particular focus on agrotechnical measures implemented in the catchment.
The quest for new clean energy sources will result in growing numbers of biogas plants and, as an implication, rising amount of waste produced in the form of a digestate. Additionally, methane fermentation becomes a growingly popular treatment method of the organic fraction of both municipal waste as well as the precipitate from wastewater treatment plants. Treatment, storage, and transport of liquid waste, such as digestate from biogas plants involve numerous challenges. Not only may ignoring them lead to economic losses but also it may cause environmental degradation. The paper discusses efficient methods for digestate management through recovery of water and nutrients that can be then utilized in the agriculture thus eliminating the temporary storage requirement. Due to increasing water deficit in agriculture, the digestate often serves not only as an alternative fertilizer but also as a source of water. Application of the reclaimed water to crop irrigation requires its proper treatment preventing contaminants from coming back to the environment. Membrane processes could deliver promising results here.
The Fenton mechanism allows for removal of difficult-to-degrade organic compounds from water, wastewater, soil, and sediments. The classic Fenton reaction takes place in acidic pH, which ensures effective hydroxyl radicals formation. Temperature and pH of the reaction environment are the key parameters affecting the Fenton process and chemistry of the reactions involved. The acidic conditions allow for dissociation of the oxygen source into radicals. On the other hand, however, they cause rapid decomposition of labile H2O2, leading to an increase in temperature of the reaction environment. Under these circumstances, there is a high likelihood of losing the oxidative potential through competitive reactions. For this reason, various modifications of the classic Fenton reaction are applied, including the use of an alternative source of oxygen (CaO2) or a different form of the reaction catalyst and/or chelating agents as well as UV radiation application. These modifications allow for an increase in pH without a significant loss of hydroxyl radicals. The research experience indicates that the degree of contaminants removal may reach even 100%, depending on the applied Fenton process configurations and reagent doses.
The aim of this study was to assess kinetics of organic (COD), nitrogen and phosphorus compound removal from sewage by activated sludge in SBRs operating on technical scale in a winter season. Additionally, a balance of nitrogen compounds in the operating cycle of the SBR was presented. The rate of organic compounds removal in the reactor's working cycle was 13.1-18.9 gO(2)/(m(3).h), of ammonia removal - 5.9-6.9 gN/(m(3).h), while the increase in nitrates was 3.3-4.9 gN/(m(3).h). Orthophosphates were released in the filling and mixing phase at an initial rate of 43.2-46.6 gP/(m(3).h) (the rate constant was 0.93-1.10 h(-1)). The orthophosphate storage rate was 16.8-23.2 gP/(m(3).h). The study demonstrated that complete ammonia oxidation occurred in the last hour of the reaction phase, which meant that the increase in the concentration of ammonia in the influent might result in an increase in the concentration of nitrogen in the effluent. On the basis of the nitrogen compounds balance in the SBR cycle, it was determined that the total amount of nitrogen removed from the sewage by denitrification and utilized for biomass synthesis was 27.02-29.62 gN/m(3), while the denitrification efficiency was at the level of 67.4-75.4%.
Calcium carbonate (CaCO3) is a substance widespread in nature and used in numerous practical applications. In nature, its biomineralization relies, among others, on microbiologically induced precipitation processes. One of such processes is precipitation induced by ureolytic bacteria. If performed in a biomimetic manner, the process is carried out under mild conditions and, most importantly, can be employed in field applications in situ. Therefore, the process constitutes an eco-friendly and energy-saving technique to be used as an ecological alternative to conventional techniques in a variety of engineering fields. In these fields, CaCO3 serves as a remediating and cementing agent, for instance to (1) clean waste- and groundwater from toxic metals and radionuclides, (2) strengthen and consolidate soil and sand, (3) seal geological formations to enhance oil recovery and geologic CO2 sequestration, (4) repair stone and concrete structures, and (5) cover surfaces of these structures with protective layers. Although already in use in the sector of protection and renovation of stone monuments, to date the technique has remained mostly under research and optimization. To become fully implementable as a reliable and economically viable technique, it still requires further research in order to address its limitations, focus on parametrical optimization, up-scaling and life-size field experiments. All these, in an interdisciplinary effort of geologists, microbiologists, chemists, civil engineers and conservators of historic monuments, will move this eco-friendly and innovative branch of engineering from laboratory to field applications in the environmental and civil engineering, geotechnology and conservation of historic buildings. Given its eco-potential and innovativeness, in this study the principles of the technique, advantages, possible applications and challenges are reviewed.
: The paper presents an innovative method of mi- crowave heating applied to anaerobic reactors for the manu-facture of biogas from the energy crops silages (maize ( Zea maize ), alfalfa ( Medicago L.), sida ( Sida hermaphrodita (L) Rusby), giant miscanthus ( Miscanthus x giganteus ) and hay si- lage). Maize silage was demonstrated to be the most ef fi cient in terms of biogas production, which amounted to 680 dm 3 /kg (per dry mass – VSS), while the least biogas (331 dm 3 /kg) was ob-tained during the fermentation of alfalfa silage. The microwave radiation clearly improved the capacity of maize, ray silage and of giant miscanthus to produce methane. For the maize silage, the methane content in the biogas increased by 18% (process performance increased from 361 dm 3 /kg to 426 dm 3 /kg). In case of alfalfa and sida silage, no effect of microwave radiation on the increase in effectiveness of methane and biogas production by fermentation process was observed. Though the nature of athermic microwave effects has not yet been clearly explained, the research conducted implies a possibility to in-tensify biochemical processes in anaerobic reactors in order to improve the effectiveness of biogas and methane production from the energy crops.
The Sea of Azov is the smallest and shallowest sea in the world with low salinity. Such properties determine its susceptibility to degradation due to anthropogenic activities. The Azovstal Iron & Steel Works in Mariupol (Ukraine) is one of the main sources of pollution of the Azov Sea. Adverse impact of the steelworks is associated primarily with the large amount of technological and cooling wastewater discharged into the sea. The paper presents the impact assessment results of wastewater discharge on the sea water quality and the ecological conditions in the discharge zone. The assessment was performed using local Ukrainian methodologies as well as applicable surface water quality standards. The comprehensive assessment was based on the three numerical integrated indicators of sea water quality: the Water Quality Index (WJW), the Water Pollution Index (WZW), the Integrated Ecological State Index (ZWSE), and the so called principle of aggregation. Based on the assessment results it was demonstrated that the wastewater discharge from the Azovstal Iron & Steel Works leads to significant increase in water pollution in the coastal zone which brings threat to the marine ecosystem and limits all types of water consumption.
Bioaugmentation method is an attractive solution to problems associated with exposure of many wastewater treatment plants to high load of wastewater pollutants. This strategy involves introduction to activated sludge an additional pool of bacteria or microscopic fungi of desired properties, capable of aggregation and adhesion, production of polysaccharide substances, biofilm formation, synthesis of bioflocculants and synergistic interactions with indigenous microorganisms, insensitive to changes in environmental parameters and of high tolerance to toxic substances. Not only may inoculation of activated sludge with such microorganisms lead to the increased biodiversity and biomass of microorganisms living in a biological reactor, accelerate the decomposrtion of organic pollutants, improve the process of biogenic compounds removal, but also prevent excessive growth of filamentous bacteria, improve sedimentation properties of sludge, counteract sludge foaming and support the process of its regeneration. Currently, great promise is held out for the development of new methods of cell delivery to the activated sludge that employ nanomaterials, prospects of using carbon nanotubes as adsorbents of toxic compounds and use of knowledge in the field of modulation of bacterial quorum sensing leading to biofilm formation. Since bioaugmentation could be employed at various stages of biological wastewater treatment, it may significantly improve the operation of wastewater treatment plants. However, this method has some limitations, related to the poor survival rates of inoculants and disappearance of their activity after being introduced into the new environment. In order to broaden our understanding of this area, it is necessary to monitor the fate and activity of inoculants using modern molecular techniques and to develop new methods of cell delivery to the active sludge ecosystem. Yet, implementation of the practices tested in the laboratory environment directly into the wastewater treatment plants remains a challenge for the future.
Despite serious questions to the theoretical fundamentals as well as the limited and outdated precipitation data, the Blaszczyk's formula for the design rainfall intensity is still in use for sizing drainage systems in Poland. The assumption of close functional dependence between the average annual precipitation depth and maximum rainfall intensities is the basis for the formula (IDF-type, i.e. intensity-duration-frequency). The assumption was verified against the actual values of maximum rainfall intensity, derived for the purpose of development and implementation of the Polish Atlas of Rainfall Intensity (PANDa rainfall model). The actual maximum rainfall intensities for different duration periods were retrieved from the precipitation records obtained from the nation-wide network of 100 rain gauges of the Polish Institute of Meteorology and Water Management (IMGWPIB) for the period of 1986-2015 These values were comparedto the corresponding Blaszczyk formula's estimates Based on the results, the basic assumption of the formula was questioned, namely that the maximum rainfall intensity values are not correlated with the normal annual precipitation depth A clear ten dency for the rainfall intensity values to be underestimated by the Blaszczyk's formula was observed It was demonstrated that the mean relative error between the actual and estimated rainfall intensities was 33% Even for the original hydrological Warsaw conditions, the Blaszczyk formula proved unacceptable due to significant underestimation of current rainfall intensities In view of the findings, a complete elimination of the formula from drainage system engineering in Poland is recommended
Municipal waste management requires national regulations to be adapted to the provisions of EU directives, especially in respect of the so-called waste management hierarchy. Segregation, recycling and raw material recovery, including energy recovery from waste, receive special attention in waste management. In particular, recovery of high-energy fractions from the municipal waste stream may constitute a potential substitute energy source for co-combustion with fossil fuels. This brings measurable environmental effects in terms of climate protection as carbon dioxide emissions from industrial installations in the biomass recovery process are considered as zero. Further, it serves diversification of energy sources, saves the natural resources and eliminates the need for landfill storage of high-calorific waste in large amounts. In Poland, co-combustion of refuse-derived fuels (RDF) is carried out in cement plants on a wide scale. In order to meet the cement market demand, nearly 200 RDF producers emerged and currently there is a significant RDF overproduction in relation to the real demand. There are still formal and technical barriers that prevent RDF combustion in the power sector and district heating, while it has already been successfully implemented in the highly developed countries. The paper investigates selected legal and technical aspects that hinder RDF usage outside the cement industry.
Applicability of coagulation technique in purification of filter washings from the swimming pool circulation system was evaluated. Removal of some of the contaminants from washings would allow for their discharge directly into the environment (e.g., for irrigation of greenery) and limiting the amount of sewage entering the sewer. In the laboratory studies, four different coagulants were used - aluminum (PAX) and ferric (PIX) - in doses ranging 1.5-6.0 mg/dm(3). In addition, the analysis of fluctuations of the values of selected physicochemical parameters (color, general suspensions, turbidity, total chlorine, total phosphorus, ultraviolet absorbance, COD and phenol index) was accompanied by the analysis of washing components (supernatant liquid and sediments) phototoxicity against the selected indicator plants - eyelash (Lemna minor) and cress (Lepidium sativum). The jar tests conducted throughout the coagulation process resulted in washings of quality adequate to be introduced directly into the environment. Regardless of the type of coagulant used, the improvement of physicochemical parameters of washings was achieved already at doses in the range of 1.5-3.0 mg/dm(3), with PAX 25, polyaluminum chloride and iron chloride(ll) mixture, being the most effective. In addition, no phytotoxic effect of both the supernatant and post-coagulation sediments was noted. Such purified washings could be employed for example in watering greenery at swimming pool areas.
Accurate dimensioning of drainage systems requires assumption of reliable design rainfall intensities as a function of its duration and probability of exceeding according to PN-EN 752:2017. Design rainfall intensities are determined by application of an adequate rainfall model that is based on statistical analysis of local precipitation time series recorded at high time resolution and covering a period of last 30 years minimum. Beside application of the obsolete Blaszczyk's formula, the Bogdanowicz-Stachy's probabilistic maximum precipitation model based on 1960-1990 rainfall records from 20 rain gauges (Institute of Meteorology and Water Management) becomes increasingly popular in Poland. However, this model does not support full coverage of the country and is based on the discontinuous regionalization. Evolving climate conditions demand validation of the model for use throughout the country. This paper presents results of verification of the actual values of rainfall intensities derived from 30-year time series from the period of 1986-2015 for given probabilities of exceeding, in comparison to the estimates delivered by the Bogdanowicz-Stachy's model. The conducted analysis undermines legitimacy of the simple regionalization concept for precipitation in Poland. Moreover, rainfall intensity values calculated by Bogdanowicz-Stachy's model for probabilities of p = 100% and p = 50% are mostly understated and for p = 20% and p = 10% are overstated in comparison to actuals (1986-2015). The results of the research confirm the need to replace Bogdanowicz-Stachy's model with "new generation" local maximum precipitation models developed as part of the PANDa (the Polish Atlas of Rainfall Intensity) atlas, not only to obtain full coverage of the country, but also to make the values of rainfall intensities reliable for design of drainage systems.
