Importance of Wastewater Treatment in Surface Treatment Industry
Over the decades, the water consumption pattern has changed dramatically. Due to the growing awareness of the importance of improving water usage across industries. Total water consumption measurements must be accurate and taken seriously. They are essential data in the design of wastewater treatment systems. Water usage in industrial processes has been neglected in favor of product quality rather than improving usage in terms of the amount of water used per unit of production. Consequently, the amount of wastewater varies greatly from one industry to another. One of the important industries that require water usage is the surface treatment industry. Therefore, it has become necessary to design and build wastewater treatment plants in these factories. Surface treatment is one of the main processes in which water is used extensively. It also generates large amounts of wastewater containing inorganic pollutants and heavy metals.
Stages of the Surface Treatment Industry
The surface treatment process includes three main stages: pre-cleaning, main surface coating, and post-cleaning. The pre-cleaning stage involves cleaning metal and non-metallic parts by degreasing to remove dirt and oils, followed by rust removal to remove rust and scale. Both processes are followed by continuous or batch rinsing with water. To remove excess chemicals from the surface of the parts. The degreasing process is alkaline while the rust removal process is acidic. The rinse water is alkaline and acidic respectively. The rinse water after degreasing and rust removal is a low-pollution stream and is the main source of wastewater, containing traces of alkalis and acids, while the degreasing and rust removal basins are highly polluted sources of wastewater.
Metals in wastewater from the surface treatment industry
The main surface coating stage after pre-cleaning includes various electroplating processes such as zinc, nickel, chromium, phosphating, tin, silver, copper, cadmium, hot dip zinc, aluminum oxidation, CED, and painting. The wastewater from this stage is highly polluted with heavy metals. The third stage – the post-cleaning stage – involves removing excess chemicals from the parts and inhibiting the coated surface. Followed by drying to obtain the desired finish, whether for functional or decorative requirements. The wastewater from this stage also contains moderate pollutants but contains traces of heavy metals. It needs effective treatment with the heavily polluted wastewater from the second stage.
Among the three stages, it is noted that the wastewater volume is divided by an average of 70% from water rinsing and 30% from concentrated basins. Divided into low-pollution streams and highly polluted streams respectively.
Separation of the resulting water
The rinsing water from the pre-cleaning stage – i.e. degreasing and rust removal – can be separated in one line to achieve the self-effect. Neutralizing and treating it separately for a primary polishing process and recovering it for use to the maximum extent as good raw water. While the concentrated wastewater from the main surface coating and post-cleaning stages can be separated. It is treated effectively to remove heavy metals and may undergo further advanced treatment stages to recover it for use in the process.
CareWater Wastewater Treatment Plant Design and Construction Service
CareWater provides the service of designing and building wastewater treatment systems. Based on process audit studies of the water consumption pattern in the technical stages of the processes. And the possibilities of recycling at the source, and removing pollutants from the basins at the source to delay the frequency of disposal. Separating the wastewater streams will be done based on detailed analysis. In this process, more than 95-97% of the wastewater is recycled. While the remaining 3% is recovered as dissolved salts, achieving zero liquid discharge.
