Methodology for determining the physical parameters of wastewater

Methodology for determining the physical parameters of wastewater discharge into surface water bodies of different types has been developed, which allows to determine the precipitation kinetics of wastewater impurities and their dependence on concomitant factors. The proposed methodology allows, based on the hydraulic size, to determine the deposition rate of particles of different size and shape contained in the wastewater and to determine the factors that affect the process of different shapes and masses particles mixing. The algorithm of measures of preliminary sewage treatment by enterprises before discharge into surface reservoirs is offered in the work. The implementation of the proposed algorithm will determine the impact of wastewater on the quality and chemically-biological composition of surface water bodies of Ukraine, as well as significantly improve the quality characteristics of surface and groundwater, which are water supply source for all residents of cities and towns of Ukraine.


Description of physical parameters of reverse waters
Depending on the aquatic environment into which the wastewater enters, the processes of pollutants destruction contained in them and their transfer rate into certain distances (or suspended impurities sediment) will depend on many factors, namely: gravity, centrifugal force, gravitational force and centrifugation [3,13].
The wastewater impurities deposition kinetics in hydroecosystems will be different and will depend on many parameters of a particular surface water body (flow rate, depth, temperature, chemical composition, density, etc.).
The main parameter in the calculation of deposition (hydraulic size) is the particles sedimentation rate to the reservoir bottom. When a particle is deposited on the reservoir bottom under the gravity action, the driving force of a solid particle with a diameter dr is described by the difference between its weight: and an Archimedean repulsive force equals the liquid weight in the volume of the particle: where ρrsolid particle density, kg/m 3 , the resistance force of the aqueous environment, in which the particles contained in wastewater fall into, according to Newton will be presented as: where ʃthe resistance coefficient of the aquatic environment, which depends on the particles deposition mode in the surface water. The deposition rate can be found from the condition of equality of force driving of the particle and resistance force of the aquatic environment into which the particle enters:

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In the laminar deposition mode at ʃ=24/Re we obtain the Stokes formula: is also a minimum particles size, when a deviation from Stokes' law is observed and at Rer ≤ 10 -4 very small particles deposition rate begins to be affected by the temperature factor of the aquatic environment molecules. Calculations have shown that at dr ≈ 0.1mcm the particles don't sediment and chaotic Brownian motion is observed.
Non-spherical particles deposition rate is less than spherical particles deposition rate. For non-spherical particles, in the formulas for the equivalent diameter dе determination, the volume Vr or the mass Gr of particles entering the aqueous medium is used: When the wastewater sedimentation, there is a limitation of deposition, which is accompanied by the collision of particles, friction between them and changes in the velocities of large and small particles. This process occurs when wastewater enters lakes or other surface water bodies where there is no flow. If the wastewater enters rivers at different flow rates, the deposition and dissolution processes of their impurities are described taking into account many physicochemical, temperature and other factors. The turbulence, coagulation and hydrodynamic complexation affect the process of different shapes and masses particles mixing in the total volume of the hydroecosystem [2].
The inhomogeneous particles separation rate in the field of centrifugal forces is higher compared to these particles separation rate in the field of gravity. The mathematical relation of the speed of the centrifugal force to the force of gravity can be carried out by comparing the accelerations acting on the particles of impurities when entering the river with a certain flow velocity in the centrifugal and gravitational fields. In general, the centrifugal force Рс (Н) is equal to: where mparticle mass (kg); G -particle weight (Н); Uoangular velocity (m/sec); rradius of rotation (m). Dilution of wastewater is a process of reducing the concentration of impurities in the reservoirs into which they discharge, caused by mixing the wastewater with the aquatic environment. The intensity of the dilution process is quantitatively characterized by the multiplicity of dilution: where Соconcentration of impurities in wastewater, discharging into reservoirs (mg/m 3 ); Сr та Сconcentration of impurities in the reservoir before and after wastewater discharging respectively. In flowing water bodies with a directed flow, the multiplicity of dilution in the calculated line n is determined by the formula: where mmixing factor, which indicates what part of the water flow in the reservoir is involved in mixing; qvolume consumption of wastewater, discharging into surface water body with volume consumption of water Q in the reservoir.
With complete mixing of the wastewater, the concentration of impurities in the reservoir at any time is equal to: where t= V/ρ+∑Q-Qпperiod of complete water exchange in the reservoir; Vreservoir volume; Qпwater consumption in the reservoir without impurities. Conection between sanitary requirements to the discharge conditions into reservoirs, ie compliance of the water composition and properties of reservoir used for water use with the established standards (Maximum Allowable Concentration) and the required degree of wastewater treatment before discharge into reservoirs in general can be described by the formula [3]: where Ссconcentration of pollutants (amount of harmful substances) of wastewater at which admissible norms will not be exceeded; qwater consumption discharge into the surface water body; Срthe concentration of the same type of pollution in the water of the reservoir above the place of discharge of the considered runoff; Qwater consumption in the reservoir; Сmpmaximum permissible concentration of pollution (harmful substances) in the water of the reservoir. The concentration of pollution m depends on many factors: the design of the outlet, the distance to the calculated line of discharge, hydraulic and hydrological parameters of the surface reservoir [4].
Converting formula (12), you can get the value of Сс, ie, the value of the pollutants concentration (harmful substances) in wastewater, which must be achieved as a result of their treatment and disposal by previous methods at enterprises: It should be noted that the conditions of wastewater mixing with the lakes and storage reservoirs are significantly different from the conditions of their mixing in rivers. The impurities concentration decreases significantly in the initial mixing zone, but complete mixing occurs at much greater distances from the place of discharge than in rivers. In addition, the mixing in time, direction and value of air velocity over lakes and storage reservoirs, which carry pollution in different directions from the discharge place. The mixing process and the chemical reactions rate that occur in lakes and storage reservoirs are influenced by the season and water temperature. Therefore, enterprises and organizations that discharge waste water into stagnant reservoirs should carry out the necessary and mandatory pre-treatment measures and make calculations of the wastewater treatment required degree according to the following algorithm: 1) to calculate the maximum permissible concentrations (MPC) of pollutants in wastewater: 2) to determine the concentration of suspended solids in wastewater: .
3) to determine the allowable value biological oxygen demand (BOD) in wastewater: 1 ( 10 ) 10 10 where Lc -BOD in a stagnant reservoir before discharge; Кdeposition rate constant О2 in a stagnant reservoir; 4) to determine the allowable value BOD in wastewater by dissolved О2: where СО2п -concentration of dissolved О2 in a stagnant reservoir before discharge; СО2п-1 -MPC of dissolved О2, which must be in the settlement line after the discharge; 5) to determine the max allowable Т о of wastewater: where Таwater temperature of surface watercourse after discharge; Твwater temperature of surface watercourse before discharge. 6) to determine the permissible content of acid or alkali in waterwater, using a set of water samples with the following chemical analysis according to the formulas: To establish the environmental risk during the discharge of wastewater to surface water bodies [14], to ensure environmental safety of surface water bodies, it is advisable to compare the experimental data with calculated by the formula [  xdistance from the source of pollution, m; gacceleration of gravity, m/sec 2

Мethodology of determination of physical parameters of reverse waters.
The results of comparing experimental data (samples taken at the mixing places of wastewater with surface waters of a small river) with the calculated ones are presented in Fig.1. It follows from the graph that the experimental results are quite accurately corrected with the calculated data.
A comparison of experimental studies results and the results obtained by formula (21) gives grounds to apply a mathematical model to predict the ecological state of reservoirs in real time to predict the spread in the water column and bottom sediments of toxic metals such as Cu, Zn, Ni, Mn and Cr.
The results of calculations (21) allow us to predict the reduction value of qualitative indicators of the pollutants concentration in surface water bodies (Fig. 2). According to the predicted results, the maximum pollutants concentration reduction in surface water bodies, after mixing with wastewater, occurs at a distance to 200 m from the mixing point.

Conclusions.
The proposed methodology to determine the physical parameters wastewater discharge into surface water bodies of different types allows: to determine the precipitation kinetics of impurities in wastewater and their dependence on concomitant factors; on the basis of hydraulic size to determine the deposition rate of different size and shape particles contained in wastewater; to determine the factors that affect the mixing process of different shapes and masses particles, the multiplicity of dilution in flowing and non-flowing reservoirs; 48 to determine the characteristics and mixing factors of wastewater in river ecosystems, lakes and storage reservoirs; to propose an algorithm of measures of preliminary wastewater treatment by enterprises before discharge into surface water bodies.
Implementation and application of this methodology will determine the impact of wastewater on the quality and chemically-biological composition of surface water bodies of Ukraine, as well as significantly improve the quality of surface and groundwater, which is a water supply source for all residents of cities and towns of Ukraine.