Waste Water Treatment Methods

for treating industrial effluents

OKO-tech waste water treatment systems can reprocess aqueous wastes with the methods described herein. Our ultra-modern and fine-tuned technology enables an extremely efficient use of these processes. As a full-range supplier, we can combine the individual processes just as needed and thus constantly achieve ideal results for our customers.

Liquids, which have different densities and are present in phases, are physically separated. Each phase can be discharged separately afterwards. The innovative sensor technology in the rotary sieve OKO-RoSi and in the OKO-select tanks determines the thicknesses of the phase layers and detects the separation layer for efficient separation. This automated separation process makes things easier for the operator and ensures process safety in wastewater treatment.

Sedimentation is the simplest way of waste water treatment: solids contained in liquids settle to the bottom due to their higher density and can be removed from there. This process takes place entirely independently. It can be described and calculated mathematically using Stokes’ law. The settling rate is calculated by means of different values, such as density of the solid substance, density of the waste water, gravitational constant and particle size. In addition, however, other factors play role such as attraction forces and repulsion forces as well as currents that are formed due to interactions between the individual substances.

The following settling rates of different substances can be taken as guidelines:

Sand, grain size 0.1 – 0.5: mm 25 to 130 mh-1
Heavy spar, finely ground: approx. 1 mh-1
Aluminum hydroxide, precipitated: 0.15 to 0.5 mh-1

The entire process is monitored and controlled by extensive sensor technology in the OKO-tech plants, thus ensuring an automated and adequate removal of sediments in our systems.

(Dissolved Air Flotation)

Flotation is a method for separating solid waste water components by adhering finest air bubbles.  Thereby, the more solid particulates rise to the water surface where they are skimmed off automatically. OKO-tech has refined this method to perfection by developing a high-performance flotation process. Even heavy and finest particulates are reliably detected, floated, and separated.

 

Finely suspended particulates are electrically neutralized by suitable charge carriers and thereby agglomerate to larger, denser units.Subsequently, these units can be separated by sedimentation or flotation. Our wastewater treatment systems provide highly effective products on the basis of natural inorganic and organic polymers that are precisely matched to this purpose.

Demulsifiers (cationic polymers) cause a charge neutralisation in the emulsifiers contained in the emulsions, thereby separating oil and water. The pH of the waste water to be treated stays the same, in contrast to emulsion breaking by acid. There is no need for neutralisation by lime water, as is necessary after splitting by acid. No product-related neutralisation sludge is produced. The costs for discharging the residues are thus considerably reduced. In OKO-tech plants, the products necessary for this process are tuned to the respective application.

Acidic and alkaline wastewaters are adjusted to a neutral pH of 6.5 to 9. They may then be discharged into the municipal sewers. Depending on the needs, this process can be carried out continuously or in a batch process within the OKO-tech waste water treatment systems. Precise sensor technology and capable control systems ensure a reliable and automated procedure.

Heavy metals have an individual pH for precipitation. When reaching this pH, they are present as largely undissolved metal hydroxides.
In order to achieve very low residual concentrations of heavy metals, precipitation as metal sulfide is required. Heavy-metal precipitation by means of organic and inorganic sulfides is also used when complexing agents are present in the waste water. Moreover, anions such as phosphate or fluorides can be removed reliably from the waste water by means of specific precipitating agents. You can choose between an OKO-tech continuous process and a batch process for this purpose also.

Precipitated metal hydroxides and other water substances precipitated by pH adjustment or reagents combine to form macroscopic flocs. These flocs will then adhere to other waste water constituents and the waste water can be treated. For supporting the flocculation process and for stabilising the flocs, diluted solutions of flocculating aids are normally used.

Separated solids are present as thin sludge first. Suitable methods dewater the sludge to a maximum extent. The result is a concentration of the constituents and the sludge is now compact. Depending on the sludge properties, we choose vibrating containers, decanters, or chamber filter presses.
If required, the waste water produced in this process is efficiently treated by the OKO-tech system solutions afterwards.

Filtration is a process for the separation or purification of substances, mostly of a suspension. Filtration is a mechanical separating process where the filter materials constitute a resistance to the particulates of the mixture to be separated. This resistance has to be overcome by pressure or vacuum.

As OKO-aquaclean flotation systems do not use any filter materials, they are an economical alternative to filtration processes. Even heavy particulates are reliably floated and separated, which is demonstrated impressively by the widespread use of flotation for ore dressing.

In oil-water separators, free oil is separated from water by gravity. The dwell time is the decisive criterion for the separation performance. Dimensioning and operation of oil separator systems are established in EN 858. If there are lightly emulsified oils in the water, we talk about unstable emulsions that can be broken by the use of coalescence separators. The effect of these systems is based on the principle of coalescence – small oily particles are caused to flow together to form large oil droplets. So, even smallest oil droplets can float to the surface according to the principle of gravity and be separated.

The basic versions of all OKO-aquaclean systems are designed as coalescers in accordance with EN 858. They stood the test of time as mobile oil-water separators, as plants for groundwater remediation and for care of cooling lubricants.

Note: Washing conditions of > 60°C and > 60 bars as well as the use of emulsifiying cleaning agents require the use of an emulsion breaking system (EBS according to EN 858) in general. OKO-aquaclean oil-water separators can be equipped as emulsion breaking systems for this purpose.

Evaporation is a wastewater treatment method for separating substances from water that are not volatile in steam. The water evaporates by heating and is condensed afterwards. What remains is a concentrate containing the non-volatile constituents of the waste water. Evaporators have a high energy demand compared with other treatment methods, either as electric current or hot steam to heat the wastewater. Depending on the wastewater, different types of evaporators are used, for example vapour-compression vacuum evaporators and atmosperic pressure evaporators, heat-pump evaporators and designs with natural circulation or forces circulation of the medium to be evaporated.