Water Research Centre Research Articles

Book Review: CHEMICAL AND BIOLOGICAL CHARACTERISATION OF MUNICIPAL SLUDGES, SEDIMENTS, DREDGE SPOILS AND DRILLING MUDS. Edited by James J. Lichtenberg, John A. Winter, Cornelius I. Webber, and Larry Fradkin. Published by Special Technical Publications, Philadelphia, 1988, 512 pp. £61.00. Reviewed by J. H. Stark, Water Research Centre, Medmenham, Henley, Bucks, U.K

Book Review: CHEMICAL AND BIOLOGICAL CHARACTERISATION OF MUNICIPAL SLUDGES, SEDIMENTS, DREDGE SPOILS AND DRILLING MUDS. Edited by James J. Lichtenberg, John A. Winter, Cornelius I. Webber, and Larry Fradkin. Published by Special Technical Publications, Philadelphia, 1988, 512 pp. £61.00. Reviewed by J. H. Stark, Water Research Centre, Medmenham, Henley, Bucks, U.K

Joint sealants in concrete structures in wet conditions: Staff report

Sealants originally introduced for the building industry have increasingly been used in civil engineering structures. To traditional materials have been added new products, apparently offering better performance, but even these have proved unsatisfactory. A major source of difficulty has been the lack of objective information for specifiers and, in particular, lack of information on the long-term behaviour of sealants, especially in situations where they are in contact with water or other liquids. CIRIA and the Water Research Centre have been investigating the problem with the aim of producing guidelines on sealants and their use. The report on the first phase, Technical Note 128, was published recently and was introduced at a symposium. This paper summarises the report and the introductory remarks at the symposium.

Control of Activated Sludge Circulation and of Secondary Settling Tank Hydraulics

The directives issued by the German Waste Water Association (ABWASSERTECHNISCHE VEREINIGUNG (ATV)) and by the British WATER RESEARCH CENTRE (WRC) in respect of the rating and control of activated sludge circuits and of the loading of secondary settling tanks of biological waste water treatment plants were studied for their applicability to papermill effluents. To this end, several years' testing was carried out on an activated sludge pilot plant and on various industrial plants. These tests revealed that secondary settling tanks of papermill effluent treatment plants may safely be rated in accordance with ATV up to a sludge volume index (SVI) of 300 ml/g and a sludge return rate of 3. If SVI values are low, the WRC process permits excessive surface loadings and is thus only practicable for high SVI levels. If sedimentation properties of the activated sludge are poor, load capacity limits are indicated more correctly by the WRC method. A simplified settling velocity method derived from the WRC process gives reliable information on the load capacity of secondary settling tanks and may readily be used for sludge circulation control.

Continuous monitoring of water quality : Arthur J Solman, Graham P Evans, Monks Risborough, United Kingdom assigned to Water Research Centre

Continuous monitoring of water quality : Arthur J Solman, Graham P Evans, Monks Risborough, United Kingdom assigned to Water Research Centre

Replacing Sand With GAC in Rapid Gravity Filters

A full‐scale study of the conversion of rapid sand filters to granular activated carbon (GAC) filter‐adsorbers was conducted by the Water Research Centre of Medmenham, UK, at the Church Wilne water treatment plant near Nottingham, England. The objectives were to identify the engineering problems associated with the change and to compare the costs and effectiveness of the GAC system with the rapid sand system. It was found that the GAC removed turbidity and residual coagulants as effectively as sand; the total organic carbon level was lower with GAC‐filtered water; longer filter runs were achieved with GAC filters; and microorganisms of health significance were effectively removed by chlorination after gas treatment.

An expert system for upgrading small water supplies

Abstract This paper describes an expert system developed by Thames Polytechnic in collaboration with the Water Research Centre (WRC) to assist in the selection of process units suitable for upgrading small water supplies. The objective of the development was to produce a system which could be evaluated more for its practical utility than for sophistication of its artificial intelligence (Al) concepts. This overall objective guided each phase of the development, from initial selection of the expert task through logical and physical design of the system to final implementation and review.

Preparation of water soluble fractions of crude oils for toxicity studies.

W. A. Maher Water Research Centre, School of Applied Science, Canberra College of Advanced Education, PO Box 1, Belconnen, ACT Australia 2616 Petroleum hydrocarbons (oils) are major contaminants of estuarine and coastal environments (Connell and Miller 1981; Knap et al 1979). Marine organisms accumulate hydrocarbons (Lee et al 1976; Morris 1974) but little is known about the effects of repeated exposures of organisms to low concentrations of hydrocarbons. The most immediate toxic and subtoxic fractions of oils are those soluble in water (Hufford 1971), toxicity of oils to organisms usually being related to the content of non-volatile persistent aromatic hydrocarbons (Neff and Anderson 1975; Zikto and Carson 1970). A widely used procedure for producing water soluble fractions of oils for toxicity studies is the slow stlrring method of Anderson et al (1974), in which an oil is layered on to water and mixed by means of a magnetic stirring bead. This paper examines the factors affecting the preparation of water soluble fractions of oils by this method. The water soluble fractions were also examined after filtration through membranes of varying pore sizes to establish the importance of particulate matter in the process of solubilization. MATERIALS AND METHODS Crude oils were obtained from commercial sources. Sea water was collected from a pr8 environment, passed through a 0.45 Bm filter and sterilized by steaming. Water extracts of oils were prepared using a mixing flask that has been previously descr8 (Maher 1982); 400 mi of sea water was poured into the flask and 1-3 g of oil layered onto the surface. The flask was placed into a thermostated water bath (200C) and magnetic stirring used to produce a turbulent layer of less than 0.5 cm depth. The water soluble fraction was removed through a tube located below the oil layer. Ai1 experiments were performed in the dark. Aliquots of water soluble fractions (I0 ml) were extracted with 5 ml of n-hexane using vortex mixing. The organic layers were

Analytical Quality Control (AQC) For Monitoring Trace Metals in the Coastal and Estuarine Environment

It is widely recognised that, unless special steps are taken, analytical results from a group of laboratories engaged in a monitoring programme are likely to be of poor comparability. This in turn can prejudice the conclusions drawn from the results of monitoring. On the basis of previous studies, the problem is known to be particularly acute for measurements of trace metals in saline waters. Recognising the difficulty, the Marine Pollution Monitoring Management Group (MPMMG) and the Water Research centre (WRc) have organised a programme of Analytical Quality Control (AQC). This has the objective of ensuring that analytical results for filterable cadmium and mercury in saline waters, obtained by water industry and other relevant laboratories, are of adequate accuracy and comparability for their intended uses. WRc is to coordinate a series of tests, some involving distributions of standards and samples, which the participating laboratories undertake; this series of tests, the background to the approach and some of the results obtained to date are described here.

Discussion Session 6

A. Campbell (Ove Arup & Pts) asked Dr Spears about the effects of drilling techniques on contamination of samples for mineralogical and pore water studies. D.A. Spears (University of Sheffield) stressed the need to take great care with drilling and sampling. In the case of the research described in the paper, the sampling was carried out by the Water Research Centre who are well experienced with work of this type.

Appraisal of the current standards for stress relaxation measurements in compression for rubbers

The current British and American Standards for stress relaxation measurements in compression for rubbers are discussed in the light of results obtained with new, highly accurate equipment, which has been developed in the Institute of Polymer Technology. This work is part of a programme sponsored by the Engineering Research Station of British Gas, the Water Research Centre and the Victaulic Company PLC, and covers the development of equipment of satisfactory performance, which is suitable for commercial exploitation, and the investigation of meaningful tests for industrial use. The present paper reports work carried out to examine the test parameters which are required in the standards and, in particular, to question the specified values of some of them. Factors which have proved to be important include loading rate and temperature, whilst mechanical conditioning has been found to be less important in determining the pattern of stress relaxation. Above all, it is essential that the measurements are of sufficient accuracy, with a closely that the measurements are of sufficient accuracy, with a closely defined initial stress, for meaningful conclusions to be drawn.

Identifying hydraulically conductive fractures with a slow-velocity borehole flowmeter

The U.S. Geological Survey used a recently developed heat-pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near Lac du Bonnet, Manitoba, Canada. The flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study. The heat-pulse flowmeter has no moving parts and operates on the tag–trace principle. It is an improved version of the flowmeter developed by the Water Research Centre in England in 1975. The U.S. Geological Survey's heat-pulse flowmeter has a flow-measuring range in water of 0.06–6 m/min, and can resolve velocity differences as slow as 0.01 m/min. This is an order of magnitude slower than the stall speed of spinner flowmeters. The flowmeter is 1.16 m long and 44 mm in diameter. It was calibrated in columns of 76 and 152 mm diameter, to correspond to the boreholes studied. The heat-pulse flowmeter system is evaluated, and problems peculiar to the measurement of very slow axial water velocities in boreholes are discussed. Key words: flowmeter, borehole flow, low flow, borehole geophysics.

Trace organic compounds in groundwater: a survey of unpolluted groundwater from three major British aquifer systems

ABSTRACT In view of the increased concern about the occurrence and persistence of organic chemicals in the environment, the Water Research Centre instigated a baseline survey of trace organics in groundwater from representative cross-sections of three major British aquifer systems. A total of 32 public and private supply boreholes in selected areas of the Permo-Triassic Sandstone, Chalk, Lincolnshire Limestone and the Great Oolite aquifers have been sampled. The areas have been chosen with the aim of characterising the organic content of ‘clean’ groundwater from the confined and unconfined zones on each cross-section. The survey was designed to encompass groundwaters of varying ages, from recent recharge in outcrop areas through to ancient waters in deep confined sections. In this way, it was expected that any compounds of anthropogenic origin would be detected only in the younger groundwaters. The total organic carbon content of the groundwaters sampled was generally very low, between 0.2 and 1.4 mg/1; low levels of aromatic halogenated hydrocarbons, which are generally taken to be contaminants, were found in many of the samples at levels above 0.01 µg/1; low levels of aromatic hydrocarbons were often detected. Although the number of compounds detected averaged 20 per sample (range: 7 to 52), few were present at concentrations greater than 0.1 µg/1. Over 100 different compounds were detected altogether but only 75 could be identified positively. Of these, nine occurred in more than half of the samples. There were no obvious differences in either compound types or levels between the confined and unconfined zones of any of the aquifers. Uncontaminated groundwater examined in this survey may be typified as having a TOC level below 0.8 mg/1, and no more than four compounds (none of which are chlorinated hydrocarbons) present at levels above 0.1 µg/1.

A comparison of two river quality models

Two deterministic river quality models are evaluated and compared by applying them to the R. Blackwater. The first model, Qual-II is a general purpose universal model developed by the United States Environment Protection Agency and the second a version of the Water Research Centre river quality model (Blackwater model) developed specifically for the R. Blackwater by Thames Water Authority but is no longer in use. After model calibration, the general Qual-II model produced a closer prediction than the Blackwater model, when compared with observed data. The main reason for the differences in the model results was considered to be the treatment of non-point input sources. The results suggest that if modelling resources are limited, the Qual-II model can be applied rather than a river specific model.

Manurial value of septic‐tank sludge on grassland

AbstractAbout 5% of the UK population is served by septic tanks and cesspits. In some districts this is applied to farmland. The Water Research Centre and South‐West Water collaborated in establishing a field trial to provide knowledge of the manurial value of septic‐tank sludge. The trial was designed to investigate the value of nitrogen (N), phosphorus (P) and potassium (K) contained in the sludge and applied over a 3‐year period to grassland. The approximate proportions of total nutrients present in the sludge applied which became available to ryegrass as inorganic fertilizer nutrients were: Barley grown in the fourth year when no sludge was applied showed a significant response to residual sludge N and P remaining in the soil. It is concluded that septic‐tank sludge can supply useful amounts of N and P, and, unlike other forms of sewage sludge, significant quantities of K to grassland. Estimates of the nutrient value should be based on analysis for dry solids, and total N, P and K. Septic‐tank sludge is usually low in metal content and no metal contamination problems should arise when it is applied to land.

Meeting of the Hydrogeological Group on 12 June 1984 at Oxford University Museum

The use of tracers as a hydrogeological tool was reviewed in four papers at this meeting and demonstrated the diversity of their use to the hydrogeologist and groundwater engineer. The use of radionuclides as groundwater tracers. S. Nixon, (Water Research Centre, Stevenage). The choice of radionuclides is subject largely to a wide range of half-lives, varying from 15 hours ( 24 Na) to 12.26 years (tritium), and to obtaining the necessary authorization to introduce these into an aquifer. The type of equipment used was shown in conjunction with a summary of several case histories including: (i) injecting radionuclides into an aquifer at controlled depths within an injection well to assess the flow of sea water leaking into a dry dock; (ii) to prove the connection of leachate in a quarry contaminating a nearby stream; (iii) to assess groundwater flow beneath a landfill in a limestone quarry; (iv) to assess the quantity of recharge entering a landslip in comparison to the total quantity of groundwater leaving it. The use of dissolved gases and natural radioactive isotopes in hydrogeological studies. J. N. Andrews (Bath University). Gases dissolved in the groundwater during recharge provide a means to investigate the climatic conditions existing during recharge and thus enabling limits to be placed on the groundwater age. The gases used in this determination include 4 He, 3 He/ 4 He, Ne, Ar, Kr, Xe, N 2 /Ar, 40 Ar/ 36 Ar and 14 C. Radio-isotopes reviewed by the author were 238 U, 234 U/ 2 3 8 U, 222 Rn and 226 Rn. The 222 Rn and 226 Rn were the most significant radioactive isotopes in the

The use of vibrating wire strain gauges for long term measurements on buried gas mains

A trial agreement concerned with the effect of adjacent deep excavations on the risk of failure of buried cast iron gas and water mains was implemented by British Gas and National Water Council on 1 January 1983. To complement this agreement, field experiments are being carried out at selected sites throughout the UK. The British Gas Engineering Research Station (ERS) is working in cooperation with the Water Research Centre to install instrumentation to measure pipe strains, joint movement, ground temperature and ground movement.Field measurements impose environmental and operating conditions of much greater severity than those encountered in a laboratory. This note outlines the site techniques developed by ERS which allow reasonably quick and reliable installation of equipment capable of withstanding the adverse conditions typical of backfilled trenches. The principle of operation of the VW gauge, its method of fixing, the factors affecting its output and the interpretation of the readings themselves are described.

Book Review: VADOSE ZONE MONITORING FOR HAZARDOUS WASTE SITES. By L. G. Everett, L. G. Wilson, E. W. Hoylman. Pollution Technology Review No. 112. Noyes Data Corporation, Park Ridge, New Jersey (1984): 251 pp. Price $36. Reviewed by Dr Lewis Clark, Head of Pollutant Pathways, Water Research Centre, Medmenham, U.K

Book Review: VADOSE ZONE MONITORING FOR HAZARDOUS WASTE SITES. By L. G. Everett, L. G. Wilson, E. W. Hoylman. Pollution Technology Review No. 112. Noyes Data Corporation, Park Ridge, New Jersey (1984): 251 pp. Price $36. Reviewed by Dr Lewis Clark, Head of Pollutant Pathways, Water Research Centre, Medmenham, U.K

A BOREHOLE MAGNETOMETRIC RESISTIVITY EXPERIMENT*

AbstractA borehole magnetometric resistivity (MMR) experiment is described in which an attempt is made to determine the extent and orientation of zones of fissuring within an otherwise massive sequence of carboniferous limestone. The region under investigation lies beneath a landfill site and the main parameter of interest is the direction of flow of ground water, which will be influenced by the orientation of the faults or fissures within the rock. The MMR method possesses some extremely advantageous features for application to hydro‐geological problems of this kind. The method is sensitive to electrical current channelling within an otherwise relatively resistive medium, and the detection of the magnetic field within the borehole does not depend upon electrical contact of the receiver with the ground. Consequently, the method can be used in dry or plastic‐cased boreholes. A direction of maximum electrical current flow is deduced from the MMR data which coincides with the predominant direction of jointing within the region.We are most grateful to the Water Research Centre, Medmenham, Berkshire, for supporting this research and particularly to Dr M. Fleet and Mr K. Beesley for their help and advice.

Accuracy of determination of total suspended solids in river waters: Analytical Quality Control in the Harmonised Monitoring Scheme

The Department of the Environment, in collaboration with the Regional Water Authorities, has initiated a Scheme for the Harmonised Monitoring of the Quality of Inland Fresh Waters in England and Wales. The Scottish Development Department has introduced a similar scheme in Scotland in collaboration with the River Purification Boards. To achieve the required comparability of results from all laboratories involved, each laboratory takes part in an Analytical Quality Control (AQC) scheme; this work is co-ordinated by the Water Research Centre. The general approach adopted to AQC has been described and this paper presents the tests made and results obtained in the determination of total suspended solids in river waters. Broadly, each of the 11 participating laboratories achieved total errors not greater than ±20% of the determinand concentration or 2 mg 1–1(whichever was the larger for different sample concentrations).

Data capture by optical scanning of published material for database enhancement

A feasibility study undertaken by the Water Research Centre to capture 30,000 items from Water Pollution Abstracts in machine readable form is reported. The equipment used to capture a one year sample of these abstracts is the Kurzweil Data Entry Machine (KDEM), a computer controlled scanning device which captures lines of text for direct output to magnetic medium. After further manipulation using word processing equipment and indexing using the ASSASSIN suite of programs, the abstracts are to be added to the publicly available database, AQUALINE. The relevance of this bibliographic material to the water industry is discussed with the aid of citation analysis of four relevant journals. The speed and accuracy of the technique is described and the final cost reported is far less than the expected cost for re‐keying the data. The technique should have widespread applications for related tasks, and should become more common as similar equipment to the KDEM becomes more readily available.