The selection of different wastewater pretreatment methods should be comprehensively considered based on the wastewater characteristics, treatment objectives, and subsequent process requirements. The following are common pretreatment methods suitable for the following scenarios:
1. Industrial wastewater contaminated with high concentrations of organic matter, suspended solids, and color (such as pharmaceutical wastewater)
Coagulation + flotation treatment involves adjusting the pH value and adding PAC and PAM for coagulation, followed by flotation separation to remove over 90% of suspended solids and color, reducing the COD to below 3000 mg/L and reducing the load on subsequent biochemical treatment.
2. Oily wastewater (such as DOP production wastewater)
Acid demulsification + flotation treatment involves acid demulsification to coagulate the oil, followed by microporous gas degreasing and flotation to separate the oil. The effluent pH is adjusted to 4.5-5.5 before entering subsequent treatment. This method is limited in its effectiveness for treating dissolved organic matter and requires integration with other processes (such as iron-carbon micro-electrolysis). 3. Wastewater containing oil and recalcitrant organic matter
Oil separation plus iron-carbon micro-electrolysis treatment: This involves removing surface oil. Iron-carbon micro-electrolysis breaks down large molecular pollutants through redox reactions, improving the biodegradability of the wastewater. Subsequent UASB plus biological contact oxidation can efficiently degrade organic matter and dehydrogenate it.
4. Raw water containing ammonia, organic pollutants, and algae
Biological pretreatment: This involves removing odorous substances and blockages through biological filters or contact oxidation, reducing the risk of blockage in subsequent processes. The water temperature must be >5°C to maintain microbial activity.
5. Recalcitrant industrial wastewater requiring advanced treatment
Chemical pre-oxidation treatment: Adding ozone or potassium permanganate before coagulation can increase the removal rate of organic pollutants and improve coagulation results.
