From the experience Metafix has gained through testing and the commercial use of its MetaWool metallic replacement cartridges, we are able to provide general guidelines for selecting and using these MRCs. This information is summarized in Table 1.

A single MiX 2000P column or two MiX 2000P columns in parallel is appropriate for all minilabs. Each column can desilver 2,500 to 3,000 liters (660 to 800 gallons) of solution and can recover 5 to 7.5 kg of silver. The effluent silver concentration after one column or two in parallel is less than 5 ppm, meeting most municipal silver discharge limits. Unlike other manufacturers' MRCs that are inconsistent and can breakthrough at any time, with Metafix there’s no need for a second cartridge as a safety back up. Single Metafix MRCs provide consistent, reliable silver recovery to extremely low levels.

Depending on the volume of silver-rich solution, one or more MiX 5000 column can be used in parallel by wholesale and professional photo processors for primary and secondary silver recovery. With a flow rate of 1L/min, one MiX 5000 column provides a desilvering capacity of 6,500 to 7,500 liters (1,700 to 2,000 gallons). Assuming an influent silver concentration of 2 g/L, the desilvering capability of one column is equivalent to a 120 amp electrolytic system working at a silver recovery efficiency of 1 gram of silver per amp per hour. Four MiX 5000 columns are equivalent to 480 amps and can desilver up to 30,000 L (7,900 gallons).

Compared to an electrolytic system, Metafix MRCs occupy significantly less space, require little maintenance, and recover more silver (typically 99.7 percent v. 90 percent with the best electrolytic systems). Metafix MRCs also eliminate the need for a separate secondary system because they maintain the effluent silver concentration to less than 5 ppm.

MiX 5000 columns can also be used by wholesale and professional photo labs as secondary silver recovery units following electrolytic systems. One column could desilver 17,000 to 21,000 liters (4,500 to 5,500 gallons) of solution containing 200 ppm of silver. Columns can be used in parallel to increase processing capacity. The effluent silver concentration is maintained well below 5 ppm.

Oliver columns can be used as a primary and secondary silver recovery system for batch processing at very high flow rates -- 8 to 12 L/min). These columns are ideal for haulers with large storage tanks. Assuming an influent silver concentration of 2 g/L and a flow rate of 10 L/min, one Oliver would be equivalent to a 1,200 amp electrolytic system working at a silver recovery efficiency of 1 gram per amp per hour.

Two or three Oliver columns can also be used in series to desilver wash water at very high flow rates (5 - 10 L/min) where silver discharge limits are extremely restrictive. One Oliver can process 30,000 liters (7,900 gallons) of water containing approximately 100 ppm of silver. The effluent silver concentration after the second or third column would be less than 1 ppm.

Important Note About pH

The optimum pH for all Metafix MRCs is 6.8 to 7.3. Solutions outside of this range could shorten the life of the columns or lead to higher effluent silver concentrations. At the point of breakthrough, the silver level in a Metafix MRC rises rapidly. Therefore, it is very important to change the column on schedule. This is best achieved through using an accurate metering station with an alarm system (e.g., a Metafix Maxi-40 or Megamizer system).

Table 1: Guidelines for selecting Metafix metallic replacement cartridges

MRC type	Application	Volume (L) capacity*	Silver (kg) capacity*	Flow rate (L/min)	Influent silver (ppm)	Effluent silver (ppm)
MiX 2000P	minilab-primary	2,500 - 3,000	5 - 7.5	0.15 - 0.5	2,000 - 3,000	<5
MiX 5000	wholesale-primary	6,500 - 7,500	10 - 15	1	2,000 - 3,000	<5
MiX5000	wholesale-secondary	17,000 - 21,000	3.5 - 4.5	1	200 - 300	<5
Oliver	haulers-batch	5,000 - 6,000	12 - 17	8 - 12	2,000 - 3,500	<5
Oliver	wash water	30,000	4	5 - 10	100	<1**

* Volume capacity and silver capacity are dependent upon input pH and silver concentration.

** Effluent silver concentration after two or three Olivers in series.

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