A water chemical model involving the complexation and solubility equilibria of calcium, magnesium, zinc, iron, manganese, silica, chloride, orthophosphate, and carbonate has been developed and applied to laboratory pipe‐loop‐coupon and field data on asbestos–cement pipe. Calculation of the saturation states of the relevant solids enables graphic guides to be prepared for the prediction of dosage levels for in‐situ pipe coating by zinc compounds as well as protection afforded by coatings formed by natural inhibitory constituents of the water.

Asbestos‐cement pipe has had a reputation for resisting attack by aggressive waters that cause corrosion of metal pipe materials. The results of this study suggest that asbestos–cement pipe behaves much like other piping materials, except PVC, that are commonly used for potable water distribution.

Increasingly, organics in water are receiving attention. According to the authors of this article, there has been no apparatus that combines the features of low cost, reliability, portability, and ease of use until now.Here is a first installment, detailing the apparatus and describing, gen erally, the ramifications of testing. In March, the JOURNAL will publish complete test procedures.*Because the concentration of CCE may vary, depending upon the method of collection and extraction, additional lower-case letters are pro posed to identify the method used to obtain the data.

Water quality analyses are very sensitive, and it is critical that the pH be measured as accurately as possible. This technique was developed after the authors observed that many water utility and research laboratory personnel follow poor techniques for determining pH.

Chlorine residual, an indication of adequate chlorination of a water supply, has a definite relationship with the bacteriological quality of the supply. This paper discusses how much, what kind of, and the proper surveillance of, chlorine residual.

The “AWWA Standard for Disinfecting Water Mains” (AWWA C601‐68) has fallen into disuse by a number of water utilities because of repeated bacteriological failures following initial disinfection with the recommended high‐dose chlorination. Other methods of disinfection, including the use of potassium permanganate and copper sulfate, do not alleviate this problem. Physical cleanliness of new mains is of primary importance and may result in successful disinfection with the low free‐chlorine residuals in distribution‐line water.

January's JOURNAL contained the description and ramifications of a new test procedure for organics in water. Here is the second installment of this two‐part article, which details the complete test procedure.*

Reported here are the results of a project that was intended to determine to what degree interferences would decrease nitrate-removal capacity of a resin when treating various waters.Nitrate in drinking water was first associated in 1945 with a temporary blood disorder in infants called methemoglobinemia, which causes serious illness and, on occasion, death when infants consume water containing concentrations greater than 10 mg nitrate nitrogen/1. Because this has occurred with sufficient frequency and widespread geographic distribution, the hazard is recogni/ed, and a limit has been assigned to the concentration of nitrate in drinking water of 10 mg/1 as nitro gen. This is about 45 mg/1 of the nitrate ion.To treat water containing nitrate exceeding the proposed EPA Drinking Water Standards (DWS), an economical nitrate removal method is needed. An ion-exchange process has been proposed and is currently being used on a low TDS concentra tion water. The purpose of this study was to determine whether or not this process would also be successful and economical for treating high nitrate concentration water when high concentra tions of other anions are also present.Most of the high nitrate concentrations in water are found in ground-water supplies. Ground waters are also likely to have other anions that compete with nitrate-exchange sites when ion-exchange resins are used for treatment. Strong anion-exchange resins will remove nitrates, but the degree of competi tion from other anions during the removal of nitrates is not clearly defined. Some of these competing anions include sulfates, chlorides, silicates, and phosphates. Iron, turbidity, and colloidal matter can cause caking or clogging problems.Eighty-two ground-water supplies having above-average nitrate concentrations were checked for variations of total dis solved solids (TDS), chlorides, sulfates, and iron. These sup plies were scattered throughout the US, and the wide range of 528 RESEARCH concentrations of these other parameters (Table 1) demon strates that the presence of nitrate is not related to concentra tions of the other parameters listed. Therefore, high nitrate levels could occur with either high or low concentrations of the other parameters. A check of some state water-supply invento ries revealed the same pattern. High TDS concentrations are related to geographical and geological location but not in any ratio pattern of one ion to another. Although no analytical results for silica concentrations were available in the previously mentioned supplies, silica is present in many ground waters. BackgroundIn 1965 a Tennessee firm 1 proposed a continuously regener ated ion-exchange process, operated with the resin moving through a closed loop, using a strong anion-exchange resin to remove nitrates from drinking water. They claim at least two advantages for their process. First, with continuous regenera tion, the waste brine is continuously produced, thereby avoid ing slug discharges to the sewer, if that is the disposal method. Second, they also claimed that...