N and P on-line meters: Requirements, maintenance and stability

State-of-the-art on-line meters for determination of ammonium, nitrate and phosphate are presented, The online meters employ different measuring principles and are available in many different designs differing with respect to size, calibration and cleaning principle, user-friendliness, response time, reagent and sample consumption. A study of Danish experiences on several plants has been conducted. The list price of an online meter is between USD 8000 and USD 35,000. Tb this should be added the cost of sample preparation, design, installation and running-in. The yearly operating costs for one meter are in the range of USD 200-2500 and the manpower consumption is in the range of 1-5 hours/month. The accuracy obtained is only slightly smaller than the accuracy on collaborative laboratory analyses, which is sufficient for most control purposes. Copyright (C) IAWQ 1996.