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UDC 628.3:62-192

Alekseev M. I., Yermolin Yu. A.

On the specific character of wastewater system reliability indicators

Summary

Authors of technical literature related to various aspects of municipal wastewater disposal systems sometimes introduce notions and definitions that concede varying interpretations which is inaccurate, particularly when using mathematical tools. Therefore, the seve­rity and definiteness of terminology under the circumstances are of special importance. The necessity, possibility and specific character of sewer reliability indicators are discussed. One of such indicators based on the hypothesis of the steady state of «failure-rehabilitation» processes is analyzed. The calculation of the introduced integrated municipal sewer reliability indicators essentially amounts to the estimation of the predictable volume of raw wastewater discharged from the system in some period because of the failure of some elements. One of the possible approaches to the solution of this problem in the context of the hypothesis of the steady origin of the sewer elements and facilities failure and rehabilitation flow is the method of segmentation and equivalenting. The ways of extending the suggested approach to an unsteady case when the failure flow rate shows seasonal periodicity or the network elements show tendency to «ageing» are designated.

Key words

sewerage network , reliability indicator , relative discharge volume , rate of failure , method of segmentation and equivalenting

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UDC 628.171:556:661.843

Boldyrev Kirill, Savel'eva E. A., Kapyrin I. V., Rastorguev A. V.

Calculations of the metal sorption parameters by the example of strontium at high sodium nitrate concentrations

Summary

For the proper evaluation of underground water protection a comprehensive analysis of pollutant migration from the pollution source is required. The problem of solution salinity effect on the substance distribution between water and water-bearing material has been insufficiently covered in literature because of the low parametric support of the widely used geochemical models and also because of the imperfection of the applied thermodynamic data bases. In the process of geochemical modeling tabular values of interfacial distribution coefficient are often used. Another approach often used in practice is transferring laboratory measured Kd values to geochemical model. The use of tabular and experimental data on interfacial distribution coefficient without proper correction can result in falsified predictions since the available Kd tabular values for metals in the process of predicting sorption parameters, as a rule, provide for a recommended value only for a definite type of water-bearing material (sand, loam, clay) and (rarely) for one or two water types which is evidently insufficient for the correct choice of Kd coefficient. High solution mineralization reduces sorption of all the components because of the competition for the sorption sections and because of metal ion complexation with the solution components. In the article the difficulties in designing the geochemical model of 90S strontium sorption at high concentrations of dissolved sodium nitrate are considered. Strontium sorption by solid phases was considered in relation to ion exchange and surface complexation. The designed model was verified versus literature data. An algorithm of geochemical modeling of dissolved substances distribution between water and hard rock is recommended.

Key words

ground water , sorption , ion exchange , water-bearing material , geochemical modeling , interfacial distribution coefficient

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UDC 628.321

Riabchikov Boris, Larionov S. Iu., Panteleev Aleksei, Shilov Mikhail

The study of enhanced water coagulation with the use of microsand

Summary

The results of the analysis of the present day advanced water coagulation equipment are presented. The results of the study showed that using the systems with sludge recycling and microsand addition was the most efficient solution. Because of the lack of reliable data on the efficiency of the given equipment, operational mode and chemical consumption, experimental units were designed that provided for testing the required modes and significant improving the process. Using sand from a packed column equipped with airlift for wa­shing produced good results. Sand loss was less than 1%. In the process of the experimental studies it was shown that the effect of fast precipitation in the clarifier at high linear water flow rate was possible. However, the use of static chemical mixing systems does not provide for the sustainable unit operation with changing parameters – flow rate, stock solution concentration, and temperature. For that reason the unit was upgraded following Actiflo option with the use of mechanical mixers for mixing with chemicals and sand, however, with sand and sludge separation in the plate column equipped with a pulsation system to improve the wash efficiency. The designed flowsheet of sludge separation into microsand and sludge with the help of a packed column showed significant advantages compared to the system with hydrocyclones. On the basis of the obtained data terms of reference for designing a pilot unit were developed.

Key words

potable water , hydrocyclone , coagulation , microsand , flocculation , static mixer , wash column

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УДК 628.17.001.4

Primin Oleg, Aliferenkov A. D., Otstavnov A. A.

Regulatory support of ductile iron pipe use in Russia

Summary

The integrity and environmental safety are among basic requirements imposed to the municipal water and wastewater systems. An appropriate choice of pipe material is of primary importance for ensuring water transportation pipeline integrity. For many years steel and cast iron have been the main pipe materials used in public water supply in Russia. Lately ductile iron pipes widely used overseas and in Russia, in the Moscow water supply system, in particular, have been competing with steel (metal) pipes. The wider use of ductile iron pipes in drinking water supply until recently was restrained by the lack of the proper regulatory framework, including general lack of instructions on the use of ductile iron pipes in Construction Rules 31.13330.2012 «Water supply. Public utilities» (Revised edition of Construction rules and regulations 2.04.02-84*). The information on these pipes and on the introduction of amendments to Construction Rules 31.13330.2012 related to the use in water supply systems, and also amendments to Construction Rules 66.13330.2011 «Design, construction pressure water pipelines and sewers with the use ductile iron pipes» in relation to their use in soft and subsi­ding soil is presented. The amendments were approved by the Ministry of Housing and Construction of Russia and put into force on April 30, 2015.

Key words

reliability , strength , pipeline , water and wastewater systems , ductile iron , set of rules

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UDC 628.147.23

Tchoukhin V. A., Andrianov A. P.

On the possible identification of biocorrosion in water supply systems

Summary

The results of the analysis of the literature data and in-house studies of steel cold and hot water pipelines subject to internal corrosion are presented. The common factor for all the studied samples was the occurrence of corrosion tubercles along the pipe inside perimeter. The study of tubercular deposits with the help of scanning electron microscopy allowed identifying four typical zones: base, core, hard coat and thin surface layer. These zones differ in structure and chemical composition. The mechanism of electrochemical and microbial induced corrosion of steel pipes is described. It is assumed that the zone under the tubercle consists of numerous corrosion electrochemical elements. On the outer edge of a tubercle corrosion occurs with oxygen depolarization, whereas inside – with hydrogen one; at that, the potentials arising during oxygen depolarization are producing a dominant effect on the formation of the outer dense layer. The hypothesis of the mechanism of tubercular deposits growth and their typical morphology is presented. On the basis of studying the properties of the deposit samples taken from the operating pipelines with the purpose of restoring the conditions of their formation the assumption on the dominant effect of microbial induced corrosion on the pipe material was made. Identification of the bacteria role in corrosion process, apart from the direct observations, can be made on the basis of determining crystalline ferric oxides formed on the surface of bacterial cell remains and their magnetosomes. The definite answer to the question on the decisive role of bacteria in corrosion of metal pipelines requires further studies.

Key words

water supply , corrosion deposits , biofilm , microbial induced corrosion , steel pipes , energy-dispersive analysis , scanning electron microscopy

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UDC 628.35:648.1

Försterling Ch., Fähnrich A., Crawford Daniel, Kühne Lothar, Barjenbruch Matthias

Wastewater recycling in small laundries using MBR-technology

Аннотация

The operation of laundries in Germany is characterized by high water and energy consumption. The business competition, increase of energy cost and active legislative requirements provide for growing demand for wastewater reuse systems (for process water treatment, heat and chemical recovery). In relation to the washing technology the level of water saving is rather high. However, the consumption of fresh water cannot be reduced unless the technologies of wastewater treatment and reuse have been integrated into the existing system. There are few if any examples of using wastewater reuse technologies for small laundries with a capacity of less than 500 kg/day; whe­reas the available water recycle systems are not efficient enough. A membrane bioreactor with flat submerged ultrafiltration membranes was installed at one of such laundries. The operation of the bioreactor provided for 93% COD reduction, and 90% water return. The quality of permeate was very high (it did not contain suspended solids or microbes) and met the requirements to the reuse in washing process. The cost analysis showed that the use of available permeate heat instead of electrical energy improved the economic efficiency of the laundry operation.

Ключевые слова

ultrafiltration , heat utilization , membrane bioreactor , laundry wastewater , water recycling , industrial wastewater treatment

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UDC 628.316

Ponomarev V. G.

Evaluation of pollutant characteristic when choosing wastewater treatment methods

Summary

The variety of pollutant characteristics in industrial effluents is considered. When choosing a treatment method in each particular case the evaluation of pollutants with testing the indicators that characterize mineral particles in suspended phase is required. Their correlation described by the first- and second order equations is disclosed. The dependences used at present for the recalculation of the laboratory data on particle hydraulic size that should be separated to provide for the required precipitation effect with the purpose of calculating the geometry of the facilities included into the project are considered. The conclusion is drawn about possible errors of the applied method of precipitation process modeling. On the basis of the research results a new indicator is suggested – agglomeration index that characterizes agglomeration capability of pollution suspended particles. The technique of its determining and the method of recalculating laboratory data on hydraulic size obtained for the layer depth differing from the settling level in the applied facility with account of the agglomeration of pollution suspended phase are presented. As shows the experience of evaluating many designed projects and technical solutions the authors of which have participated in tenders a large number of these solutions are not supported by the analysis, do not have enough proofs and are often a fortiori incorrect and consequently cheap. Therefore tender boards find difficulties in making an objective choice.

Key words

suspended substances , Agglomeration , wastewater , settling kinetics , agglomeration index , hydraulic size

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УДК

Бестраншейное восстановление внутриквартальной канализации с заменой колодцев

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UDC 628.336.515

KOZLOV M. N., Kevbrina M. V., Kolbasov G. A., Agarev Anton, Shashkina P. S.

The key results of the full-scale studies of sludge digestion technology with biomass recycle

Summary

For a number of years the specialists of R&D Centre of «Mosvodokanal» JSC have been developing and testing in a lab environment the technologies that can enhance the process of wastewater sludge digestion within the existing capacity of the treatment facilities. As a result a method was chosen which provided for thickening a part of sludge with subsequent thickened sludge returning back into the digester. The important advantage of this method is the possibility of increasing sludge retention time as dry matter without increasing the hydraulic retention time with simultaneous biomass retaining. Therefore, the required decomposition rate is provided in smaller size reactors. In the course of studying the process solutions on wastewater sludge digestion optimization the method of biomass recycle showed itself as the most economically viable. During the full-scale studies of the recycle option the decomposition of the ash-free basis increased in average to 56.6% (42.2% reference value) which was confirmed by the significant improvement of sludge dewatering properties. The average biogas yield increased by 3%. In the course of the experimental studies no adverse effects of the sludge recycling technology on the digester performance were observed. The results obtained during the full-scale studies evidence the long-term benefits of introducing the technology of wastewater sludge digestion with biomass recycle at the Moscow wastewater treatment facilities.

Key words

anaerobic fermentation , methane tank , decomposition of organic matter , biomass , sludge thickening , recycle