Manual for testing of water and wastewater treatment chemicals
Report No 1184/1/04
A large number of chemicals are used in the production of potable water and in the treatment of wastewater effluents. In potable water treatment chemicals such as inorganic salts and polymeric organic coagulants are used for primary coagulation, as coagulant aids and for sludge dewatering; lime and soda ash allow for pH correction and water stabilisation; caustic soda is used for pH adjustment; powdered activated carbon (PAC) can remove taste and odour compounds and micropollutants such as atrazine; bentonite aids coagulation; and ammonium hydroxide is used in chloramination.
Wastewater treatment is generally performed using a predominantly biological process in South Africa, but here too chemicals are often used, such as coagulants for sludge conditioning, lime for pH adjustment and to increase the alkalinity content, and aluminium and iron salts for phosphate removal.
However, standardised testing procedures for assessing these process chemicals are seriously lacking in this country. There are some recommended tests available for the assessment of some of these chemicals, such as the South African Bureau of Standards 459-1955 Standard Specification for Lime for Metallurgical Purposes, but the tests described in this specification are for the most part outdated gravimetric procedures which are time consuming.
In the case of polyelectrolytes used for primary coagulation in potable water treatment, there is currently no legislation or regulation system present in this country for the control of these chemicals and no standard tests are available to measure the effectiveness of these chemicals for coagulation. Prior to 1994 all suppliers needed to supply Department of Health certification before their products would be considered for use by UW, but this certification appears to have been issued on an ad hoc basis, subject to the supplier being able to supply approval or certification for his product or the monomer/s from a recognised world health body such as the World Health Organisation (WHO), the United States Environmental Protection Agency (USEPA) and the European Economic Community (EEC). After 1994 the issuing of such certification by the Department of Health fell away altogether. Water utilities such as Umgeni Water insist that recognised certification is supplied by the polyelectrolyte supplier before using his product, but this system is considered inadequate since it lacks uniformity. The Department of Health is presently in the process of implementing a regulatory system for polyelectrolyte control, but this is not expected to be functional for some time yet.
Similar problems are experienced with sludge treatment coagulants, since tests available for the assessment of these polyelectrolytes don't necessarily adequately describe the performance of these chemicals for dewatering. At present, no national standard for testing these chemicals exists.
Problems also arise in assessing powdered activated carbon (PAC). A number of tests are available to measure various parameters such as iodine number, methylene blue number, phenol number and molasses number. Bodies such as the American Water Works Association (AWWA), the American Society for Testing and Materials (ASTM) and the Council of Chemical Manufacturers' Federations (CEFIC) have standard procedures for conducting such tests, but at present there is no uniformity in South Africa regarding the test procedures used. For example there are three different phenol tests available (Chemviron Carbon, 1998), the most commonly used being the German Standard DIN19603 (1969). There are also two AWWA methods, one for PAC and another for granular activated carbon (GAC). The same is true for iodine number and methylene blue number, at least two or three standard tests being available in each case.
In addition to this, these parameters, although useful for production quality control, are not particularly effective for assessing the operating performance of the carbon in terms of micropollutant removal (Chemviron Carbon, 1998). In the experience of the authors, a low iodine number generally indicates that the carbon will not be effective for taste and odour removal, but a high iodine number gives no indication of the ability of the carbon to adsorb these micropollutants. Since micropollutant removal is the usual application of activated carbon in water treatment, it has been necessary for a number of Southern African Water Authorities to devise an alternative method for assessing this parameter.
The lack of any standardised testing procedures makes it difficult to assess or compare these products, or to conduct routine quality control tests on them, which could even result in negative health and environmental implications. There are also no standard procedures available for conducting tender evaluations of these chemicals. Therefore Umgeni Water, in conjunction with the Water Research Commission, undertook to collate and evaluate the various test procedures available for assessment of the most commonly used chemicals in the water and wastewater treatment industries, resulting in the production of this manual. The manual attempts to address a number of these inadequacies and contains standard tests, many of which can be conducted using relatively simple equipment, procedures for evaluation of process chemicals, standard worksheets for the various tests as well as spreadsheets for those tests requiring calculations.
There were three main objectives of this project:
Initially a literature survey was conducted in order to gather all available test procedures for the following water and wastewater treatment chemicals:
polyelectrolytes for primary coagulation and as coagulant aids
polyelectrolytes for sludge dewatering
inorganic coagulants (e.g. aluminium sulphate, ferric chloride)
lime (quicklime and slaked lime)
oxidants and disinfectants (e.g. hypochlorite, chlorine dioxide, ozone, hydrogen peroxide, bromine)
Once this had been done, a number of the main role players in the water and wastewater industry in Southern Africa were consulted regarding the test procedures which they use. Institutions, water authorities and companies which collaborated with the authors by providing test procedures, information and chemicals are listed below:
City of Cape Town
Nelson Mandela Metropolitan Council
Most of the tests were evaluated in the Research and Development Laboratories, Umgeni Water to determine their accuracy, repeatability, limit of detection and the ease with which each test could be performed and its value in assessing a particular chemical. Emphasis was placed in selecting tests that not only analysed critical factors for a treatment chemical, but which were both accurate and simple wherever possible. Whenever a test required sophisticated instrumentation, attempts have been made to provide an alternative that can be conducted using simpler technology.
i.iii Summary of Manual
This manual is divided into 9 chapters, the first being an introduction and the last containing reference details, while Chapters 2 to 8 deal with test procedures for logical groupings of water and wastewater treatment chemicals, these being:
Chapter 2: Coagulants
Chapter 3: Coagulant Aids
Chapter 4: Sludge Treatment Coagulants
Chapter 5: pH Adjustment and Stabilisation Chemicals
Chapter 6: Oxidants and Disinfectants
Chapter 7: Activated Carbon
Chapter 8: Fluoridation Chemicals
Where relevant worksheets have been included at the end of a section or method to assist the user in entering the necessary data and carrying out calculations.
The methods contained in the manual have been taken from a wide variety of sources including Standard Methods for the Examination of Water and Wastewater, the America Water Works Association (the ANSI/AWWA methods), the American Society for Testing and Materials (ASTM), the Council of Chemical Manufacturers' Federations (CEFIC), the German Standard DIN Standards as well as tried and tested methods from the Umgeni Water Laboratories and from the collaborators mentioned in Section i.ii above.
This has resulted in a manual that provides testing procedures for most of the chemicals used in water and wastewater treatment in Southern Africa, that are generally fairly simple to conduct and which are reliable and repeatable. It is hoped that this manual will offer the first step towards providing standardised procedures for the evaluation of water and wastewater treatment chemicals and assist in providing the technical background for future legislation governing the use of these chemicals.