Inside-Out and Outside-In UF Membrane Cleaning Agent & Cleaning Scheme Selection

Maintenance

The comparison of outside-in UF membrane before and after cleaning

Generally, every chemical cleaning takes 6 hours. The time it takes depends on the circulating and soaking period as well as the time for cleaning agent and equipment preparation. Online measure the permeability of UF membrane before and after every chemical cleaning method to evaluate the cleaning effect.

Contaminant Types & Cleaning Agent Selection

You may refer to the table below to help you choose the cleaning agent, bactericide type and concentration.

Contaminant Types & Cleaning Agent Selection
Contaminant	Cleaning Agent & Bactericide	Cleaning Agent Concentration
Bacteria, organics	Sodium hypochlorite	500 ppm (active chlorine)
Organics, silicon oxide	Sodium hydroxide	5% below
Organics	Nitric acid, hydrochloric acid, sulfuric acid	5% below
	Oxalic acid	2% below
	Citric acid	5% below
	EDTA	0.4% below
Bacteria	Sodium hypochlorite	10–100 ppm

Outside-In UF Membrane Cleaning Scheme

Outside-In UF Membrane Cleaning Scheme
Solution	Range of Application	Cleaning Scheme
Alkaline cleaning solution	Organic fouling	Prepare 0.1%–0.5% sodium hydroxide solution with water (calcium carbonate hardness < 60 mg/L); Circulate the alkaline solution in the system for 20–30 minutes under standard pressure and flow, and then soak for 0.5–1 hours; Circulate the alkaline solution in the system for 20–30 minutes under standard pressure and flow, discharge the cleaning solution, and then flush with fresh water.
Sodium hypochlorite cleaning solution	UF membrane fouling caused by organics and living organisms	Prepare 1000–5000 ppm sodium hypochlorite solution and 0.1% mass fraction sodium hydroxide solution with water (calcium carbonate hardness < 60 mg/L); Circulate the cleaning solution in the system for 20–30 minutes under standard pressure and flow, and then soak for 0.5–2 hours; Maintain the concentration of the sodium hypochlorite solution; Circulate the cleaning solution in the system for 20–30 minutes under standard pressure and flow, discharge the cleaning solution, and then flush with fresh water.
Acid cleaning solution	Inorganic fouling (iron fouling and carbonate crystal fouling)	Prepare 0.1%–0.5% acid solution (2% hydrochloric acid or 2% citric acid) with water ; Circulate the cleaning solution in the system for 20–30 minutes under standard pressure and flow, and then soak for 0.5–2 hours; Circulate the alkaline solution in the system for 20–30 minutes under standard pressure and flow, discharge the cleaning solution, and then flush with fresh water.

Inside-Out UF Membrane Cleaning Scheme

Inside-Out UF Membrane Cleaning Scheme
Solution	Range of Application	Cleaning Scheme
Alkaline cleaning solution	Organic fouling	Prepare 0.05% sodium hypochlorite solution (by active chlorine) or 0.1% sodium hydroxide solution (by weight percentage) with water (pH ≤ 10); Circulate the alkaline solution in the system for 20–30 minutes under standard pressure and flow, and then soak for 0.5–1 hours; Circulate the alkaline solution in the system for 20–30 minutes under standard pressure and flow, discharge the cleaning solution, and then flush with fresh water.
Acid cleaning solution	Inorganic fouling (such as iron)	Prepare 1%–2% citric acid solution (by weight percentage) or 0.1% hydrogen chloride solution (by weight percentage) with water (pH ≥ 2); Circulate the acid solution in the system for 20–30 minutes under standard pressure and flow, and then soak for 0.5–1 hours; Circulate the acid solution in the system for 20–30 minutes under standard pressure and flow, discharge the cleaning solution, and then flush with fresh water.