Provision of water supply in the city of Mykolayiv
01 September 2022
In April 2022, the city of Mykolayiv was left without a centralized domestic and drinking water supply due to damage as a result of hostilities to the Dnipro-Mykolayiv water pipeline, which supplied water from the Dnipro River (the water intake is located within the Kherson region) to the water treatment facilities of the city of Mykolayiv and then, after cleaning and disinfection, water supply networks of centralized domestic and drinking water supply to end users.
Starting from May 16, 2022, the centralized water supply of the city of Mykolayiv is carried out by supplying technical (untreated) water from the water intake of the Buzki estuary and artesian wells according to the schedule through the city's drinking water supply pipeline system.
In a letter dated June 20, 2022 No. 05-70/1362/5-22, the deputy head of the regional military administration, V. Haydarzhi, reported that: "... the main problem of ensuring centralized drinking water supply in the city of Mykolayiv, in connection with the transition to water intake from the Southern Bug River (Buzky estuary), consists in reducing the content of salts, hardness and other chemical elements" and sent to our address the indicators of chemical-bacteriological, radiological and hydrobiological analyzes of the water of the Buzky estuary for the period from 01.05.2022 to 31.05.2022 for DSTU (National Standard of Ukraine) 4808:2007 "... for the possibility of processing by scientific specialists and providing recommendations on the use of national and European technologies for its purification in order to bring indicators to drinking quality."
According to the content of dissolved substances, which is also confirmed by the results of water analyses sent to our address, the water of the Buzki estuary belongs to the salt group according to the generally accepted classification of natural waters. Usually, such water, even after cleaning by traditional methods, causes an excessive level of corrosion, which leads to the rapid failure of any, including special, transportation systems, including the distribution system of steel pipelines for drinking water supply.
Specialists of the National University of Water and Environmental Engineering conducted a study of water samples taken from the Mykolayiv water supply network in order to establish the real level of corrosiveness (corrosive aggressiveness) of water and to select an effective corrosion inhibitor according to the requirements of the Standard of the Housing and Communal Economy of Ukraine SOU ZHKH 42.00-35077234.010:2008 "Systems of centralized household drinking water supply and communal heat supply. Anti-corrosion protection. General requirements and methods of control".
According to test protocol No. 723 dated 06/21/2022, a water sample taken from the Mykolayiv water supply network has the following physical and chemical properties: dry residue (total mineralization) – 6368.0 mg/dm3; chloride content - 3050.0 mg/dm3; sulfate content - 434.3 mg/dm3; total hardness - 25.1 mmol/dm3; alkalinity – 4.5 mmol/dm3; total iron - 0.282 mg/dm3, residual chlorine - not detected.
Corrosion tests were carried out in accordance with the general requirements of DSTU (National Standard of Ukraine) 3895, GOST (National Standard) 9.905, GOST (National Standard) 9.908 using corrosion indicator P5126 according to DSTU 2681 and EP sensors, which have cylindrical steel 20 electrodes with a diameter of 6 mm and a length of 31 mm, which are the primary transducers. The specified measuring equipment is prepared for use in accordance with DSTU (National Standard of Ukraine) ISO 10012, DSTU (National Standard of Ukraine) 3989.
It was established that the corrosiveness of the water supplied by the centralized economic and drinking water supply system in the city of Mykolayiv is dangerous (more than 0.2 mm/year) with a tendency to point (fistula) corrosion.
So, from the moment technical (untreated) water was supplied from the Buzki estuary water intake and artesian wells, the process of accelerated corrosion damage to the city's water supply networks was launched, as a result of which numerous emergency situations can be predicted in the near future. The problem is complicated by the supply of water according to the schedule, which leads to increased corrosion. Thus, the water analysis dated July 7, 2022 recorded an increase in the amount of iron in the city's pipeline system to the level of 1.78 mg/dm3, which indicates a catastrophic acceleration of pipeline corrosion.
If urgent measures are not taken, the likely consequences may exceed the damage caused by the destruction caused by shelling and bombing of the city, which is currently being carried out by the aggressor country.
The Standard of the Housing and Communal Economy of Ukraine SOU ZHKH 42.00-35077234.010:2008 in the case of the fifth (emergency) degree of corrosion provides for the urgent implementation of anti-corrosion protection measures and elimination of the causes of emergency corrosiveness of water. The main steps of anti-corrosion protection of pipelines are the use of corrosion inhibitors and the creation of a protective coating. Simply stopping the water supply to the pipelines does not solve the problem, because it will increase the level of corrosion several times.
Conducted studies on the selection of a corrosion inhibitor showed the high efficiency of the use of the complex-acting drug "Microstat™". A mixture of poly- and low-molecular electrolytes" according to TU U 20.1-41972832-002:2020 (the main active substance is polyhexamethyleneguanidine hydrochloride and phosphate - PGMG). The drug "Mikrostat™" at a dose of 0.05-0.5 mg/dm3 reduced the corrosiveness of water taken from the Mykolayiv water supply network to the normative values of 0.02-0.05 mm/year.
In the specified doses, the drug "Microstat™" also disinfects water at the maximum permissible concentration of polyhexamethyleneguanidine in drinking water of 1 mg/dm3. The safety of this substance is confirmed by the following documents. In particular, "... active substance: 30%-polyhexamethyleneguanidine hydrochloride.", "...belongs to the 4th class of danger (low-hazardous substance) when injected into the stomach and applied to the skin ....,..... no reveals mutagenic, cumulative, embryotoxic, gonadotoxic and carcinogenic properties." "Residual concentrations ... in drinking water should not exceed 1.0 mg/l of the active substance." (Conclusion of the State Sanitary and Epidemiological Examination No. 602-123-20-5/36572 dated August 28, 2018). In addition, "... active substances: polyhexamethyleneguanidine hydrochloride and/or polyhexamethyleneguanidine phosphate - a total of not less than 10.0%.", "... belongs to the 4th class of low-hazardous substances when injected into the stomach and applied to the skin." "Does not cause skin resorptive and sensitizing effect, has no cumulative effect. Does not reveal mutagenic, carcinogenic, embryotoxic, gonadotropic, teratogenic properties." (Conclusion of the State Sanitary and Epidemiological Examination No. 12.2-18-5/8394 dated April 17, 2020).
The National University of Water and Environmental Engineering proposed to fully restore the drinking water supply of the city of Mykolayiv according to a temporary scheme using a new effective single-stage reagent water purification technology (NEOTROn), which is intended for use in emergency situations (ES) of a natural, man-made and military nature.
Reagents used in NEOTROn technology: flocculants with disinfecting properties of the "Microstattm" type and disinfectants based on chlorine dioxide of the GO2tm type during water treatment for BOS and KOS, as well as in field conditions - are guaranteed to destroy all bacteria and viruses, including viruses hepatitis A (and even SARS-CoV-2 viruses).
Based on the results of the volunteer work of specialists in the field of water supply and drainage from the USA, Israel, and Ukraine, united by the scientific park "Innovative technologies of the Rivne region" of the National University of Water and Environmental Engineering (NUWEE) in Rivne, with the direct participation of international experts, proposals were formed regarding the organization water supply of the city of Mykolayiv in the current situation, with which NUWEE appealed to the Head of the Mykolayiv Regional State Administration Kim V.O.
The following recommendations are offered:
In the first stage, during the period of supply by the surviving networks of economic and drinking water supply of the city of Mykolayiv, technical quality water from the Buzhsky estuary, and local wells, to ensure the mandatory adoption of measures for anti-corrosion protection of the networks, by organizing proportional to water consumption during the period mentioned above of supply of a polymer-based complex action drug of the guanidine series - "Microstat™" (it has biocidal properties and inhibits the processes of electrochemical corrosion). Corrosion tests and research on the selection of a corrosion inhibitor carried out by the NUWEE proved that the corrosiveness (corrosiveness) of the water currently supplied by the system of centralized household and drinking water supply in the city of Mykolayiv is emergency (more than 0.2 mm/year) with a tendency to point (fistula) ), and the effectiveness of the use of the drug of complex action "Preparation "Microstat™". A mixture of poly- and low-molecular electrolytes" according to TU U 20.1-41972832-002:2020 - high (reduction of water corrosivity to normative values of 0.02-0.05 mm/year and disinfection of water at a dose of 0.5 mg/dm3). The selection of the inhibitor was carried out in accordance with the requirements of the Standard of the Housing and Communal Economy of Ukraine SOU ZHCH 42.00-35077234.010:2008 "Systems of centralized household drinking water supply and communal heat supply. Anti-corrosion protection. General requirements and control methods" from among those allowed in Ukraine for use, including in drinking/domestic water supply based on the current conclusions of the State Sanitary and Epidemiological Examination.
In the second stage, organize the external water supply of the city of Mykolayiv using one of the existing water intakes from the South Bug River (not the Bug estuary). According to our data, the construction of the technological scheme of water purification now remains intact and can be put into operation with minimal costs. It recommends the use of NEOTROn technology to obtain drinking water. It is based on a new scheme of combined use of preparations based on chlorine dioxide and flocculants with disinfecting properties based on polyelectrolytes in the preparation of natural low-turbid colored waters. This significantly increases both the efficiency of the use of each individual drug, as well as the efficiency of cleaning and disinfection of the water undergoing treatment, as a whole, by eliminating the possible disadvantages of the different use of the above-mentioned reagents. The NEOTROn technology, combining all the necessary components, ensures the production of potable water with normative values of corrosion aggressiveness, can be implemented both in field systems from flexible tanks and at existing water treatment plants, guarantees effective cleaning and disinfection, excludes secondary pollution during transportation by existing water supply networks, ensures their preservation.
The appeal of the management of NUWEE in connection with the existing problems of Mykolayiv water supply to the association of water utilities of Ukraine led to the creation of a working group on water quality of the WASH cluster, which held several meetings.
Based on the questions that the representatives of the WASH cluster water quality working group began to raise, they began to familiarize themselves with the existing problems, first of all, the corrosion of pipelines. Specialists of the group study and discuss the possibility of using in the current situation, liming, pH correction, the use of corrosion inhibitors based on inorganic polyphosphates, express their assumptions about the safety of using a whole group of reagents/preparations approved for use in drinking/economic-drinking, technical water supply on the basis of the conclusions of the State Sanitary and Epidemiological Examination of Ukraine. The main issues are to identify the cause of the intensification of corrosion processes, including the possible destruction of the previously formed protective layer of sediment on the inner wall of the pipelines.
Scientific specialists of the park have proposed an option to improve the operation of the Mykolayiv water supply system, which involves the use of the above-mentioned complex preparation that can stop the corrosion processes of water pipes. The final version of the proposals will be formed after research by specialists of the scientific park of pipeline corrosion processes directly in the city of Mykolayiv.