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UDC 504.064:628.356

Rublevskaya O. N., Probirsky M. D., Leonov L. V.

Implementation of the technologic solutions focused on the prevention of water body eutrophication (best practices of SUE «Vodokanal of St. Petersburg»)

Summary

SUE «Vodokanal of St. Petersburg» has been the biggest water user in the Baltic Sea coastal zone; therefore the enterprise is obliged to meet the regulations of effluent discharge into the water bodies. The qualitative composition of the discharged effluents is regulated not only by the Russian standards but also by the international recommendations including the Helsinki Convention on the Protection of the Marine Environment of the Baltic Sea. Russia endorsed the Convention in 1998. Since that moment Saint-Petersburg and Vodokanal have been aiming at reducing raw wastewater discharges into the Baltic Sea and meeting the regulations of the effluent quality. The best practices of SUE «Vodokanal of St. Petersburg» implementing the technology of nutrients removal with the purpose of preventing water body eutrophication are presented. The international experience was studied; the laboratory and full-scale tests of different technologies of enhanced phosphorus and nitrogen removal were conducted. Kreal technology and its limitations revealed in the process of operation are described alongside with the process schemes designed by the University of Cape Town (UCT-Process) and Johannesburg University (JHB-Process) and implemented with the purpose of improving the efficiency of wastewater treatment. In order to provide for the stable phosphorus concentration in the effluent according to the regulations chemical removal of phosphorus was introduced. Starting from 2011 Saint-Petersburg has been fully meeting the HELCOM recommendations.

Key words

treatment facilities , wastewater , aluminium sulphate , total phosphorus , total nitrogen , eutrophication , ferrous sulphate

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UDC 628.35

Rublevskaya O. N., Kolosov D. E., Veresova M. V., PANKOVA G. A.

Studies of the toxicological effect of aluminium compounds on the activated sludge biocenosis in aeration tanks

Summary

To provide for eliminating phosphorus from wastewater in the process of tertiary treatment in order to inhibit the eutrophication of the receiving water bodies iron- and alumunium containing chemical are used. At the wastewater treatment facilities operated by SUE «Vodokanal of St. Petersburg» chemical removal of phosphorus from wastewater was carried out with imported ferrous sulfate (III); beginning from 2012 domestically-produced aluminium sulfate has been used. Transfer to aluminium sulfate was supported with a series of experimental and research studies; one of them aiming at studying the toxic effect of aluminium and ferrous (III) salts on activated sludge in aeration tanks. The review of different assessments of the toxicity of aluminium compounds in relation to plants and animals in general is presented; the results of individual studies of the aluminium sulfate and ferrous (III) sulfate effect on the activated sludge biocenosis in aeration tanks are presented. During the analysis mixed liquor samples treated with different chemical dosages were fed with acetate ions and aerated for 18 hours under similar conditions; after that the sludge samples were subject to microscopic examination. The absence of any toxic effect of aluminium sulfate on the sludge biocenosis at the metal concentrations up to and including 64 mg/l was shown which exceeded the chemical dosages used in practice dozens of times. During the introduction of higher dosages of aluminium sulfate or ferrous sulfate the inhibition of aquatic life was caused by pH decrease; whereas at pH correction with alkali liquor no symptoms of the biocenosis inhibition was noticed. Further increase of chemical and alkali dosages up to 1000 mg/l as aluminium or iron caused the inhibition of aquatic life because of the total solids increase which is fatal for the fresh water biocenosis.

Key words

aeration tank , aluminium sulphate , aluminium , toxic effect , activated sludge resistance , resistance of indicator microorganisms of activated sludge

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UDC 628.16.065.2.001.2

Strelkov A. K., Egorova Yu. A., Bykova P. G., Erchev V. N., Dudarev V. A., Kichigin V. I.

Research in Possibility of Low Turbid Water Treatment under the PFS-1 of Samara Conditions

Summary

The flow chart of water treatment with an aluminium oxychloride coagulant in combination with flocculant Magnafloc LT20 in winter and during the spring flood has been proposed and tested under production conditions. It is established that the quality of water taking into account permanganate oxidation, residual aluminium, colour and turbidity has improved. It is proved that the efficiency of disinfection in the course of coagulation treatment with aluminium oxychloride is 1,5–2 times higher than with aluminium sulphate. It makes it possible to reduce the dose of chlorine at the primary disinfection and to reduce accordingly the possibility of formation of organochlorine compounds. Due to reduction of an aluminium polyoxychloride dose the sliming at treatment facilities is reduced up to 30% that makes it possible to reduce the discharge of suspended matters and residual aluminium from the station. Manufacturing expenses and water losses go down, conditions of facilities disinfection improve, which guarantees the epidemic safety of water.

Key words

turbidity , chromaticity , residual aluminium , aluminium sulphate , sliming , epidemic safety

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UDC 628.345.1

Rublevskaya O. N., Kolosov D. E., PANKOVA G. A.

Substantiating the use of aluminium sulfate for the elimination of phosphorus from wastewater at the Saint-Petersburg wastewater treatment facilities

Summary

The article opens a series of three articles dedicated to the introduction of aluminium sulfate as a chemical for chemical removal of phosphorus compounds from wastewater. The urgency of the task of eliminating nutrients from wastewater is described; the primary concern of removing phosphorus for the protection of water bodies from eutrophication is substantiated. A short literature review including the practice of chemical removal of phosphorus from wastewater in USA and European Union is presented. Special features of the basic chemicals – calcium, aluminium and iron compounds – essential for the practical application of chemical removal of phosphorus are described. The second article will present the evaluation of the toxicity of aluminium and iron compounds; the results of investigating the impact of iron and aluminium salts on the aeration tank biocenosis and sludge mixture dewaterability will be discussed. The third final article will present a detailed report on the introduction of aluminium sulfate as a chemical for chemical removal of phosphorus compounds from wastewater at the Saint-Petersburg wastewater treatment facilities.

Key words

wastewater , aluminium sulphate , nutrients removal , chemical precipitation of phosphorus , ferric sulfate , insoluble phosphates

DOI 10.35776/MNP.2020.06.05
UDC 628.161.2:628.169:675.024

Chursin V. I., Panfilov E. V.

Precipitation of dyes from spent solutions using magnesium-containing agents

Summary

Spent solutions generated in the process of skin dyeing make a significant negative contribution to the pollution of the total amount of wastewater of the enterprise; hence, the need arises for their local treatment to reduce the concentration of organic dyes before discharging into the total wastewater flow. The aim of the work was to study the possible use of magnesium-containing agents for the precipitation of dyes from local wastes. The experiments were conducted with simulated solutions of acid dyes that differed in molecular structure and the number of auxochrome groups to ensure the solubility of the dye and its adsorption by the dyeing material. Dyes were precipitated using magnesium-containing agents, i. e. suspension of magnesium hydroxide and magnesium oxide (MagPro), and for comparison, aluminium sulfate. The efficiency of the precipitation of dyes from solutions was evaluated by the amount of separated precipitate and the optical density of the supernatant. The effect of the precipitation agent consumption on the efficiency of removing dyes from the solution is shown. The results of the experiment provided for establishing the optimal consumption of precipitation agents for each of the dyes used. It was found that aluminum sulfate and MagPro were equally effective with respect to the direct brown solution. The acid black dye is predominantly precipitated with aluminum sulfate, while Luganyl brown NG is precipitated only with magnesium-containing agents. To precipitate dyes from local effluents with an equal precipitate yield, the consumption of MagPro agent is 10 times less than while using aluminum sulfate. MagPro is more effective in sedimentation and discoloration of local effluents after skin dyeing at pH above 12.

Key words

settling , aluminium sulphate , absorbency , local wastes , dyes , magnesium-containing agents , magnesium hydroxide , discoloration of solutions

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UDC 628.161.3

Getmantsev S. V., Sychev A. V., Getmantsev V. S.

Prospects of coagulation water treatment

Summary

Despite the significant progress and increasing popularity of membrane water treatment methods chemical treatment keeps hol­ding tightly its position. One of the most important characteristics of coagulants based on polyaluminium chloride is the basicity. The basicity, all other conditions being equal, determines the dealkylation rate and pH of water subject to coagulation. The value of pH obtained after coagulant hydrolysis, in its turn, determines the zeta potential of colloids present in water and kinetic persistence of the colloid system. During coagulation each type of colloid water pollutants has corresponding optimal pH value. The development of the technology of polyaluminium chloride production from high-purity metallic aluminium by «Aurat» JSC resulted in market launch of EPOKHA™ coagulant trademark with 40–83% basicity. The use of EPOKHA™ provides for choosing an optimal modification of polyaluminium chloride for every customer and every climatic season. Another new product manufactured by «Aurat» OJSC under GranEKO™ trademark is crystalline aluminium chlorhydrate with 65–83% basicity. The concentration of active matter in such product is up to 50% as Al₂O₃. High basicity provides for using GranEKO™ for the clarification of water with low alkaline reserve eliminating the use of alkalizing agents. An important trend in developing chemical water treatment means is the development of composite chemicals combining inorganic coagulant and organic polyelectrolyte. New composite chemicals of ERCHV™ series present a combination of coagulant based on aluminium salt, polydiallyldimethylammonium chloride and modifying additives that provide for the synergetic effect and storage stability. The variety of characteristics of water subject to treatment and applied process flow schemes require an integrated approach to the problem of pH correction during coagulation by using coagulant with higher or lower basicity and changing the injection point.

Key words

coagulation , residual aluminium , aluminium sulphate , aluminium polyoxychloride , chemical water treatment methods , basicity

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UDC 628.162

Gandurina L. V., Gavrilova N. N., Kuzin E. N., Raff P. A.

The use of the dynamic light scattering method for characterizing humic acids in natural water

Summary

The results of studying the impact of sodium, calcium and aluminium salts on the dispersive characteristics of humic acids in natural water with the use of Photocor Compact-Z analyzer are presented. The dispersiveness of humic acids by molecular mass determines to wide extent the efficiency of natural water decoloration with aluminium salts. It is shown that the method of dynamic light scattering can be an efficient and rapid method of studying the conformational changes of macromolecules in alkaline and acid solutions, and chemical interactions between humic acids and metal ions. The studies were carried out with natural and simulated water prepared by extracting humic acids from peat with distilled water and blending the obtained solutions to the required color. The ion composition of simulated water was changed by adding calcium chloride, aluminium sulfate, «Aqua-Aurat™30» polyaluminum oxychloride, sodium hydrogen carbonate and hydrochloric acid.

Key words

chromaticity , natural water , aluminium sulphate , aluminium polyoxychloride , humus acids , alkalinity , light scattering

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UDC 628.168.4

Gandurina L. V., Getmantsev S. V., Raff P. A., Nikiforova A. Ju.

Chemical aspects of decoloration of low turbidity natural water with aluminium salts

Summary

The mechanism of decoloration of natural water with aluminium sulfate aluminium polyoxychloride is considered. The complexing reactions of humus acids with aluminium salts mainly contribute to the decoloration of natural water. The parallel proceeding reaction of aluminium sulfate and polyoxychloride hydrolysis facilitates the reduction of aluminium ion concentration in treated water but does not reduce color. Empirical dependences of coagulant dosages on color and alkalinity of raw water have been determined. Higher efficiency and lower dosages of aluminium polyoxychloride compared to aluminium sulfate used for decoloration are stipulated by the polymer origin of aluminium polyoxychloride. The use of coagulants in combination with cationic Praestol 650 flocculant provides for improving the efficiency of decoloration by 10–20% at the optimal coagulant: flocculant ratio of 50:1 for aluminium polyoxychloride and 20:1 for aluminium sulfate.

Key words

chromaticity , natural water , aluminium sulphate , cationic flocculant , aluminium polyoxychloride , humus acids , alkalinity , hydrolysis , complexing

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UDC 628.161.3

KINEBAS A. K., NEFEDOVA E. D., Gvozdev V. A., Rusanova L. P.

The efficiency of using aluminium polyoxychlorides in natural water purification

Summary

SUE «Vodokanal of St. Petersburg» has been continuously upgrading water treatment technologies with the aim of improving the quality of water services. The results of laboratory, pilot and industrial approbations provided for the data on the use of more than 160 samples of coagulants based on the salts of different polyvalent metals. Among them are aluminium-, iron-, and titanium-based coagulants and also their composite compounds. Investigating more than 50 samples of aluminium oxychloride produced both by local and foreign manufacturers showed that for such special water source as the Neva River the use of chemicals of low and medium base strength in the processes proceeding in contact clarifiers is most preferable. The use of aliminium oxychloride did not result in sharp decrease of alkalinity or pH at the increased coagulant dosages. The residual alkaline reserve in water allows introducing higher chemical dosages which results in improving the efficiency of the first water treatment stage at low temperatures of the water source (less than 4 °С) and reducing filter cycle. SUE «Vodokanal of St. Petersburg» has adopted the concept of using the range of coagulants during different year seasons.

Key words

coagulant , aluminum oxychloride , aluminium sulphate , pilot tests