Sorption, coagulation, and biodegradation for graywater treatment

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Sustainable Materials

Background:

• Growing populations and climate change intensify water scarcity.
• Graywater recycling is a potential solution but hindered by high treatment costs.
• Biochar presents a low-cost, eco-friendly alternative sorbent for graywater treatment.

Purpose of the Study:

• Compare biochar and activated carbon (AC) for removing dissolved organic carbon (DOC) from graywater.
• Evaluate the effectiveness of pretreatments (coagulation, biodegradation) on graywater treatment.
• Assess the potential for graywater non-potable reuse using these methods.

Main Methods:

• Tested five biochars and activated carbon for DOC removal from graywater.
• Investigated the impact of coagulation and biodegradation pretreatments.
• Measured removal of UV absorbance, DOC, and free chlorine demand.

Main Results:

• A wood-based biochar was most effective among tested biochars, though AC removed more DOC.
• Sorption alone did not meet graywater regulations; pretreatment was necessary.
• Biodegradation pretreatment enabled AC and biochar to meet irrigation and toilet flushing targets at specific doses.

Conclusions:

• Pretreatment, particularly biodegradation, is essential for effective graywater treatment using biochar or AC.
• Combined pretreatment and sorption can reduce turbidity and increase UV transmittance, facilitating UV disinfection for non-potable reuse.
• This integrated approach offers a viable strategy for sustainable graywater management.