HANDBOOK 3 WATER POLLUTION

Transcription

1 HANDBOOK 3 WATER POLLUTION Manual Flow-proportional Sampling of Wastewater and Estimation of Load NREB Natural Resources and Environment Board DANCED Danish Co-operation for Environment and Development

2 HANDBOOK 3 WATER POLLUTION Manual Flow-proportional Sampling of Wastewater and Estimation of Load Erling Povlsen January 2002 COWI Consulting Engineers and Planners Danwaste

3 Handbook 3 Water Pollution Manual Flow-proportional Sampling of Wastewater & Estimation of Load 1 st Edition (1 st Print) January copies The Author and Danced Copenhagen Quotation permitted with source credit Printed by UM Colour Printing Company Report No. SUD-02-53

4 Table of Contents FOREWORD 1 1. Background and sampling strategy Representative sampling 3 2 Procedures Sampling procedure Preparation of composite samples Preservation of sample Laboratory analysis Estimation of load 10

5 FOREWORD In June 1999, the State Government of Sarawak, in collaboration with the Danish Co-operation on Environment and Development (DANCED), initiated the Sustainable Urban Development Project in Sarawak (SUD) to implement an Environmental Management System (EMS) for the city of Kuching. An important part of an Environmental Management System is the continuous monitoring of the quality of the environment and the load discharge to the environment from the different types of sources. The monitoring allows the management to identify the need for strengthened efforts to reduce the impact on the environment from the activities of the society. As part of the monitoring system, the effluent concentrations and loads of pollutants in sewage and wastewater from households, food outlets (markets, restaurants, food centres, coffee shops etc.), industries and pig farms are important parameters. This handbook describes the sampling procedure and the procedure of estimation of load of pollutants from individual sources. This is the third book of the series, which deals with standard methods and procedures for specific measurements pertaining to river pollution in Kuching, Sarawak. 1

6 I would like to take this opportunity to record our gratitude to DANCED for its support. In addition, I would like to record our appreciation to many individuals from various Federal and State Government departments, who provided valuable support and cooperation in this matter. "TOWARDS INTEGRATED ENVIRONMENTAL QUALITY MANAGEMENT" CHONG TED TSIUNG Acting Controller of Environmental Quality / Project Director Natural Resources and Environment Board / Sustainable Urban Development Project SARAWAK 2

7 1. Background and sampling strategy The EMS for Kuching includes measurements of effluent concentrations and estimation of loads of pollutants in sewage and wastewater from point sources (households, markets, restaurants, food centres, coffee shops, industries, pig farms etc.). Measurement of effluents comprise different types of procedures which each has to be standardised and documented carefully: Collection of samples Analysis of samples This handbook deals with the first issue. To ensure proper measurement, the collected samples must be representative for the wastewater in question. This implies that the sampling procedures must take into account the possible variations in discharge with time. E.g. the discharge from industries vary greatly when speaking on batch-processing while the variations typically are less in fully continuous processes. In addition, measurements of the water flow and sampling must be carried out simultaneously, because information on the amount of water discharged is needed for the estimation of load of pollutants. Samples may be taken by hand or automatically. This handbook deals with manual sampling. 1.1 Representative sampling A sample should be taken in a way that will represent the wastewater being discharged in a certain time. No matter how good the laboratory analysis is, the laboratory data will not be correct if the sample was not properly collected. 3

8 With large variations in composition and flow rate, getting a representative sample can be quite difficult. Careful thought, planning, and training must be used to develop and carry out a good sampling program. Basically there are two types of sampling for wastewater: 1) Grab sampling 2) Composite sampling Re 1) Grab sampling Grab sampling is the collection of a single sample of wastewater. This type of sample yields data about the wastewater at one time and place. Grab sampling can be used when the concentration of a parameter under consideration is not expected to vary significantly with time. Re 2) Composite sampling A composite sample yields data about the wastewater over a longer span of time. Composite samples are generally used when the concentration of the parameter under consideration is expected to vary with time. There are two types of composite samplings: Time proportional composite sampling, which is the collection of a series of grab samples of equal volume sampled at specific time intervals over a certain time period and combined to form a composite sample. Flow proportional composite sampling, which is the collection of a series of grab samples the volume of which changes in proportion to the flow. The flow proportional composite sampling is run for a specific period of time often with a 2-hour interval between each collection. 4

9 Flow proportional composite sampling will be used for sampling of wastewater and sewage in the context of the EMS for Kuching. This method is the most accurate for estimation of load from point sources with variable effluent flow and concentration of pollutants in wastewater and sewage. 2 Procedures 2.1 Sampling procedure The sample must be collected at the outlet from the premises at, or immediately before the point where the effluent enters the drain or stream, which is carrying the wastewater from the site. In case there is no specific outlet point (simple overflow), or the outlet is not accessible, or the discharge point of the outlet is beneath the water surface of the drain or the stream the sample should be collected inside the premises as close to the outlet as possible. The sample should not be collected in the drain/stream, where dilution of the wastewater has taken place. In new approvals of polluting activities (EIAs, licenses, permissions) or renewal of existing approvals it should be made a standard condition that a sampling point along the pipe between the discharging activity and the outlet should be easy accessible for water sampling (sampling well). Prior to sampling any rubbish, mud or the like, which may block or reduce the flow at the outlet, is removed. Flow measurements and sampling are carried out every second hour during a specified period of time (depending on the operation/opening time of the premises (usually during a period of 8-16 hours). When deciding on the period of time, it must be considered that discharge of pollution might take place outside normal working hours. The flow measurements and the collection of samples are carried out as follows: 5

10 At each sampling round a sampling bucket of 5-10 litres capacity is placed at the sampling point at the outlet from the premises The time it takes to fill the bucket is recorded by the use of a stopwatch. All the water from the discharge has to be collected. If the flow is too large for using a bucket, the flow is measured by the use of a triangular (right-angled) weir. The flow can be 5 estimated from the formula Q H, where Q = water flow (in litre/sec) and H = the distance from the tip at the bottom of the triangular to the water surface in the triangular (in dm) (c.f. Figure 1). Figure 1. Triangular weir After the flow measurement a wastewater sample is collected in a pre-labelled sampling glass bottle. It is important that a glass bottle and not a plastic bottle is used, because the water has to be analysed for organic compounds. The lid of the bottle 6

11 is removed without touching the inner surface of either. The bottle is held well below the neck and is plunged it into the effluent. It must be ensured that the hand is always downstream of the bottle opening. The bottle is recapped and placed it in a cooling box containing a sufficient quantity of ice packs. The following should be observed during sampling: The sampling containers and sampling devices must be clean and uncontaminated. Before the sample is taken, the container should be rinsed several times with the wastewater. During sampling, the collector must wear protective gear (at least gloves, but also goggles and waders may be needed). If there is no wastewater flowing at any time during sampling, this must be recorded. Occurrence of rainfall during sampling is noted The bottles containing the samples must be kept in the cooler box throughout the entire collection process. 2.2 Preparation of composite samples When all samples has been collected a composite sample is prepared by mixing the individual sub-samples collected in proportion to the flow at the time of sampling. The volume of each of the sub-samples which is required for the composite sample is estimated from the following formula: AR FS SC x, Where AF NS 7

12 AR = Amount of sub-sample required for the composite sample (litres) FS = Flow at sampling time (m 3 /hour) AF = Average flow (m 3 /hour) SC = Size of composite sample (litres) NS = Number of sub-samples Table 1 presents an example of estimation of the volume of each sub-sample using this formula. In the example five sub-samples were collected for an 8 hours composite sample with a 2 hours sampling interval. In the example a 2 litre composite sample is needed and the average flow is 7 m ) /hour (( ), c.f. Table 1.) 5 The flow during the sampling of sample 1 is 6 m 3 /hour. The amount of sample 1, which is needed for the composite sample, can be estimated as follows using the formula above: 6 2 AR x 7 5 AR = 0.34 litres The estimated required volumes of the other samples using the formula are indicated in Table 1. 8

13 Table 1. Flow-proportional composite sampling. Example of estimates of volumes of sub-samples required for the composite sample Sample Sampling time from start (hours) Flow at sampling time (m 3 /hour) Volume of sample required for the composite sample (litre) Sample Sample Sample Sample Sample The total size of the composite sample depends on the number of analyses of different parameters. The size can be estimated from the volumes required for analysis of each parameter which is indicated in Table 2 below. When mixing the sub-samples into other containers, the contents of each should be well mixed before pouring. 2.3 Preservation of sample When the composite sample has been prepared, the sample is split into sub-samples for analysis of individual parameters and conserved. Table 2 provides an overview of required volumes for different parameters, preservation methods and holding time. 2.3 Laboratory analysis The composite samples from households, food outlets and pig farms are analysed for BOD, COD, TSS, Ammoniacal Nitrogen, Tot-N, Tot-P and Oil & Grease. The composite samples from the industries are analysed for BOD, COD, TSS, Ammoniacal Nitrogen, Tot-N, Tot-P, Oil & Grease, Arsenic, Cadmium, Chromium (hexavalent and Total), Copper, Cyanide, Iron, Lead, Manganese, Mercury, Nickel, Boron, Tin, Zinc, Phenols, Sulphides and AOX. 9

14 The methods of analysis to be applied are indicated in Table 3. Table 2. Recommended volume needed for analysis and preservation of sample of different parameters Volume required for Preservation Holding time analysis ml Biochemical oxygen 1000 Cool 4 o C, exclude 72 hours demand (BOD ) air Chemical oxygen 250 Add H 2 SO 4 to ph 2 72 hours demand (COD) Total suspended solids 1000 None 24 hours (TSS) Ammoniacal Nitrogen 400 Cool 4 o C. Add 24 hours (NH 4 -N) H 2 SO 4 to ph 2 Total nitrogen (Tot- 500 Cool 4 o C. Add 24 hours N) H 2 SO 4 to ph 2 Total phosphorous 50 Cool 4 o C 24 hours (Tot-P) Oil & Grease 1000 Cool 4 o C. Add 24 hours H 2 SO 4 to ph 2 Mercury Add 6 ml 10% 28 days K 2 Cr 2 O ml H 2 SO 4 per litre Other Metals 250 Add HNO 3 to ph 2 6 months Cyanide (CN) 500 Cool 4 o C. Add 72 hours NaOH to ph 12 Phenols 1000 Add H 3 PO 4 to ph 4 28 days and 5 ml 20% Cu SO 4 Sulphides 50 Add 2 ml zinc acetate 24 hours AOX 500 Add HNO 3 to ph 2 1 month 2.4 Estimation of load The load of different pollutants from each individual point source is calculated from the average flow during the sampling period and the concentration of the pollutant in question in the composite sample. 10

15 Table 3. Parameters for which the collected samples are analysed. The methods of analyses for each parameter are indicated Method of Analysis. Biochemical oxygen demand (BOD ) APHA 5210 B 1995 Chemical oxygen demand (COD) APHA 5220 B 1995 Total suspended solids (TSS) APHA 2540 D 1995 Ammoniacal Nitrogen (NH 4 -N) APHA NH 3 C 1995 Total nitrogen (Tot-N) APHA 4500-N B 1995 Total phosphorous (Tot-P) APHA 4500-P D 1995 Oil & Grease APHA 5520 B 1995 Arsenic (As) Cadmium (Cd) Chromium ( Cr hexavalent) Chromium (Cr total) Copper (Cu) Cyanide (CN) Iron (Fe) Lead (Pb) Manganese (Mn) Mercury (Hg) Nickel (Ni) Boron (Bo) Tin (Sn) Zinc (Zn) Phenols Sulphides AOX 11