This article provides general information on the considerations to be taken into account in the design of treatment facilities.
There are certain considerations that must be taken into account when designing wastewater treatment plants. These can be grouped under two main headings: pollution loads and discharge criteria. Discharge criteria can further be divided into subcategories such as recovery, receiving environment discharge, garden irrigation, etc. The diversity of discharge criteria primarily stems from regulations, prohibitions, and standards set by official institutions and organizations. In line with the guidance of official institutions or regulations, commercial entities producing wastewater determine the most suitable treatment method for themselves and make the necessary investments.During the implementation of these investments, we, as Environmental Engineers, are requested to find the fastest and most accurate solution in the shortest possible time. In response to such a demand, all design, manufacturing, assembly, and commissioning activities are completed within a few months according to the plant capacity, and the wastewater treatment plant is delivered in operational condition. While the design process of industrial wastewater treatment plants and the selection of appropriate processes may take months or even years solely through laboratory studies, how do we manage to fit this process into a very short timeframe?**Pollutant Parameters Requiring Special Attention**When designing plants, detailed analysis reports of the wastewater owned by companies are examined to determine the times when pollution loads and flow rates peak. Based on these values, the necessary storage systems are selected, followed by the appropriate treatment method. Depending on the pollutants contained in the wastewater and the discharge criteria, suitable physical, chemical, or biological methods are applied. However, in some cases, all these systems can be used together, and even ozone oxidation and membrane filtration systems can be included in these systems.I anticipate the question of what criteria are used to determine the selection of these systems. First and foremost, it should be checked whether the wastewater contains Chromium (Cr+6) or Cyanide (CN–) according to the detailed analysis report. If bIf one or both of these two harmful chemicals are present, the wastewater must be collected separately and subjected to appropriate pre-treatment processes. If these pre-treatments are not applied, the desired removals in wastewater treatment will not be achieved, resulting in a liquid waste with extremely toxic effects. In addition to these two toxic chemicals, an examination of other heavy metals and pollutants present in the wastewater should be conducted to determine the appropriate treatment method. When determining the appropriate treatment method, parameters such as COD, BOD, pH, and oil grease in the wastewater should be monitored.In wastewater treatment facilities, it is generally observed that the ratio of BOD to COD values is between 0.4 – 0.8. However, in wastewater containing only heavy metals, this value approaches 0 (zero), while the opposite situation can be seen in some industries. Wastewater with high COD and low BOD values can be treated using physical and chemical methods, whereas wastewater with high BOD values requires a biological treatment process after these treatment systems.In the exceptional case where the BOD/COD value is above 1, the factors that elevate the BOD value need to be investigated. For this purpose, raw wastewater is filtered through filters of different pore sizes, and BOD, COD, and TOC analyses are performed on the filtrate. If, after the filtration process, the BOD value is lower than the COD value, the wastewater should undergo sedimentation or various physical treatment processes before chemical and biological treatment processes, and then continue with appropriate treatment processes. However, if the BOD value is still higher than the COD value after the filtration processes, an appropriate biological treatment process should be selected for BOD removal, followed by a design according to discharge or reuse criteria. While designing, it is necessary to monitor not only the BOD, COD, and TOC parameters in the wastewater but also parameters such as Total Nitrogen, Total Phosphorus, and Ammonium Nitrogen. If the concentrations of the mentioned parameters (nutrients) are not at the desired levels, the necessary nutrient addition for biological treatment should be made.It is necessary to be done.
After the BOD value is reduced by the applied biological treatment process, the wastewater is subjected to appropriate chemical treatment or filtration processes to achieve the desired discharge quality parameters, allowing for the discharge of water.
The explanations provided above are written as general principles, and the processes that can be selected may vary significantly when considering factors such as the pollution loads contained in the wastewater, the area where the treatment facility will be established, the purposes of establishing the treatment facility, etc.
For this reason, it is advisable to seek technical support by consulting with expert and experienced engineers before making the correct choice.
