ICS 13.060.20  
 
Reference number  
DRS 564: 2023  
© RSB 2023  
  
 RWANDA 
STANDARD  DRS  
564 
 
First edition  
2023 -mm-dd 
 
Ambient water  — Specification  
   
DRS 564: 2023  
©RSB 2023  - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2023  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
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Rwanda Standards  Board  
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ePortal: www.portal.rsb.gov.rw   Formatted:  German  (Switzerland)
Field  Code  ChangedFormatted:  German  (Switzerland)
Formatted:  German  (Switzerland)DRS 564: 2023  
iii                ©RSB 2023  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  3 
4 Requirements  ................................ ................................ ................................ ..............................  54 
4.1 General requirements  ................................ ................................ ................................ ................  54 
4.2 Specific requirements  ................................ ................................ ................................ ................  54 
5 Ambient water quality guidelines and monitoring  ................................ ................................ .. 76 
5.1 Ambient water quality guidelines  ................................ ................................ .............................  76 
5.2 Ambient water quality monitoring  ................................ ................................ ............................  87 
5.3 Water quality parameters of measurement, timing and frequency for monitoring  .............  97 
6 Sampling  ................................ ................................ ................................ ................................ ... 109 
6.1 General  ................................ ................................ ...........................  Error! Bookmark not defined. 9 
6.2 Sampling programmes and techniques  ................................ ................................ .................  109 
Annex  A (informative)  Ambient water quality parameters of measurement  ................................  1110 
 DRS 564: 2023  
©RSB 2023  - All rights reserved                  iv 
 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratifie d by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 564 was prepared by Technical Committee RSB/TC 013, Water and Sanitation . 
Committee membership  
The following organizations were represented on the Technical Committee on Water and Sanitation  (RSB/TC 
013) in the preparation of this standard.  
Rwanda Water Resources Board  
Water and Sanitation Corporation Ltd  
Kigali Water Limited  
Rwanda Housing Authorit y 
Shine Engineers Multi -Sectoral Company Limited  
SINA Gerard Enterprise URWIBUTSO  
University of Rwanda/College of Sciences and Technology  
AYATEKE Star Company Ltd  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 564: 2023  
v                ©RSB 2023  - All rights reserved  
 Introduction   
Ambient water bodies are categorized into two types: surface waters (e.g. rivers, lakes , streams , …) and ground  
waters (springs, boreholes, …) . These contribute to domestic and industrial water supplies, agricultural practices 
and fisheries, as well as sup porting natural biota. Therefore, their water quality should be managed so as not to 
cause any adverse effect, including the conservation of aquatic ecosystems. The ambient water quality 
standards are registered for protecting water bodies, having regard t o their type and water usage in many 
countries. The control of pollutant from point sources such as domestic sewage and industrial waste water 
treatment plants should be implemented by setting the effluents standard, taking into account the dilution factor  
and the natural purification capacity of the receiving water bodies. In other words, the ambient water quality 
standard is a basic tool for every water quality management activity.  
With reference to SDG6.3.2, the quality status of individual water bodies is classified based on the compliance 
of the available water quality monitoring data for the core parameters with target values defined by the country. 
The indicator is computed as the proportion of the number of water bodies classified as having good qual ity (i.e. 
with at least 80 % compliance) to the total number of assessed water bodies, expressed as a percentage.  
Ambient water contributes to various activities and uses as well as the conservation of  natural ecosystems. 
Monitoring is conducted to examine  compliance with the standards. Both frequency and choice of site are very 
important in quality monitoring. Water quality must be evaluated comprehensively, using various data taken 
from several sampling points.  
 
 DRS 564: 2023  
1                ©RSB 2023  - All rights reserved  
 Ambient water  — Specification  
1 Scope   
This Draft Rwanda Standard  specifies requirements , sampling  and test methods for  ambient  water .  
2 Normative references   
The following documents are referred to in the text in such a way that some or all of  their content constitutes 
requirements of this document.  For dated references, only the edition  cited applies. For undat ed references, the 
latest edition of the referenced document (including any amendments) applies.  
RS ISO 7887, Water quality — Examination and determination of colour  
RS ISO 7888, Water quality — Determination of electrical conductivity  
RS ISO 7027 -1, Water quality — Determination of turbidity — Part 1: Quantitative methods  
RS ISO 11923 , Water quality — Determination  of suspended solids by filtration through glass -fibre filters  
RS ISO 6059 , Water quality — Determination of the sum of calcium and magnesium — EDTA titrimetric method  
RS ISO 10523 , Water quality — Determination of pH  
ISO 5814 , Water quality — Determination of dissolved oxygen — Electrochemical probe method  
RS ISO 5815 -2, Water quality — Determination of biochemical oxygen demand after n days (BODn) — Part 2: 
Method for u ndiluted samples  
RS ISO 6060 , Water quality — Determination of th e chemical oxygen demand  
RS ISO 10304 -1, Water quality — Determination of dissolved anions by liquid chromatography of ions — Part 
1: Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate  
RS ISO 11732 , Water quality — Determination of ammonium nitrog en — Method by flow analysis (CFA and 
FIA) and spectrometric detection  
ISO 15681 -1, Water quality — Determination of orthophosphate and total phosphorus contents by flow analysis 
(FIA and CFA) — Part 1: Method by flow i njection analysis (FIA)  
RS ISO 15681 -2, Water quality — Determination of orthophosphate and total phosphorus contents by flow 
analysis (FIA and CFA) — Part 2: Method by continuous flow analysis (CFA)   
©RSB 2023  - All rights reserved                  2 
 RS ISO 9297 , Water quality — Dete rmination of chloride — Silver nitrate titration with chromate indicator (Mohr's 
method)  
ISO 6703 -3, Water quality — Determination of cyanide — Part 3: Determination of cyanogen chloride  
ISO 10359 -2, Water quality — Determ ination of fluoride — Part 2: Determination of inorganically bound total 
fluoride after digestion and distillation  
RS ISO 22743 , Water quality — Determination of sulfates — Method by continuous flow analysis (CFA)  
RS ISO 5961 , Water quality — Determination of cadmium by atomic absorption spectrometry  
RS ISO 9174 , Water quality — Determination of chromium — Atomic absorption spec trometric methods  
RS ISO 8288 , Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame atomic 
absorption spectrometric methods  
RS ISO 6332 , Water quality — Determination of iron — Spectrometric method using 1,10 -phenanthroline  
RS ISO 6333 , Water quality — Determination of manganese — Formaldoxime spectr ometric method  
RS ISO 12846 , Water quality — Determination of mercury  — Method using atomic absorption spectrometry 
(AAS) with and without enrichment  
RS ISO/TS 17379 -2, Water quality — Determination of selenium — Part 2: Method using hydride generation 
atomic absorption spectrometry (HG -AAS) 
ISO 9390 , Water quality — Determination of borate — Spectrometric method us ing azomethine -H 
RS ISO 17378 -2, Water quality — Determination of arsenic and antimony — Part 2: Method using hydride 
generation atomic absorption spectrometry (HG -AAS)  
RS ISO 12020 , Water quality — Determination of aluminium — Atomic absorption spectrometric methods  
RS ISO 8165 -1, Water quality — Determination of selected monovalent phenols — Part 1: Gas -chromatographic 
method after enrichment by extraction  
RS ISO 8165 -2, Water quality — Determination of selected monovalent phenols — Part 2: Method by 
derivatization and gas chromatography  
RS ISO 9377 -2, Water quality — Determination of hydroca rbon oil index — Part 2: Method using solvent 
extraction and gas chromatography  
ISO 16265 , Water quality — Determination of the methylene blue active substances (MBAS) index — Method 
using continuous flow analysis (CFA)  DRS 564: 2023  
3                ©RSB 2023  - All rights reserved  
 RS ISO 15089 , Water quality — Guideli nes for selective immunoassays for the determination of plant treatment 
and pesticide agents  
RS ISO 9308 -1, Water quality — Enumeration of Escherichia coli and coliform bacteria — Part 1: Membrane 
filtration method for waters  with low bacterial background flora  
RS ISO 9308 -2, Water quality — Enumeration of Escherichia coli and coliform bacteria — Part 2: Most probable 
number method  
RS ISO 4831 , Microbiology of food and animal feeding stuffs — Horizontal method for the d etection and 
enumeration of coliforms — Most probable number technique  
ISO 5667 -1, Water quality — Sampling — Part 1: Guidance on the desi gn of sampling programmes and 
sampling techniques  
3 Terms and definitions   
For the purposes of this standard, the follow ing terms and definitions apply . 
3.1 
ambient water  
open waters such as surface waters (e.g. rivers, la kes, streams , …) and ground  waters (springs, boreholes,…) 
as opposed to closed water supply systems that distribute treated water or wastewater.  
3.2 
ambient water quality  
quality refers to  natural, untreated water in rivers, lakes and ground  waters  and represents a combination of 
natural influences together with the impacts of all anthropogenic activities.  
3.3 
aquifer  
geological water -bearing formation (bed or stratum) of permeable rock, or unconsolidated material (e.g. sand 
and gravels) capable of yield ing significant quantities of water  
3.4 
general treatment  
treatment of water using coagulation, flocculation, clarification and filtration followed by disinfection   
©RSB 2023  - All rights reserved                  4 
 3.5 
groundwater   
water in the saturated zone and/or unsaturated zone of an underground geological formation or artificial deposit 
such as made ground, e.g. fill material  
3.6 
inland surface water  
any standing or flowing water on the surface of the land extending up to the boundary of the coastal water  
3.7 
lake 
inland body of stand ing surf ace water of significant extent  
3.8 
river  
large stream which serves as the natural drainage for a basin  
3.9 
simple treatment  
simple filtration and boiled at 100 ⁰C  
3.10 
simple filtration  
process of separating suspended solid matter from a liquid, by causing the latter to pass through the pores of a 
membrane, called a filter.  
3.11 
stream  
flowing body of water in a natural surface channel. Surface water: Water which flows over, or lies on, the ground 
surface  
3.12 
parameter  
water quality variable or characteristic of water quality, also called a determinant  DRS 564: 2023  
5                ©RSB 2023  - All rights reserved  
 3.13 
non-point -source pollution   
pollution of water bodies from dispersed sources such as fertilizers, chemicals and pesticides used in 
agricultural activities  
3.14 
point source  pollution :  
pollution with a precisely located origin  
4 Requirements  
4.1 General requirements  
4.1.1  The quality and safety of ambient water shall be p eriodically monitored in order  to reflect accurately 
the scientific knowledge on the kind and extent of all identifiable effects on health , welfare and environment that 
may be expected from the presence of pollutants in any body of water.   
4.1.2  No person shall discharge, deposit or em it any pollutant into the inland surface waters to exceed the 
quality of mbient  Water  
4.1.3  The competent authority shall be responsible for the maintenance of the quality of inland surface 
waters . 
4.1.4 The ambient water shall be in the following six (6) classes:  
a) Class A  – Water that requires simple treatment, for drinking;  
b) Class B  – Bathing and contact recreational water;  
c) Class C  – Water suitable for aquatic life;  
d) Class D – Water source that require to undergo general treatment process, for drinking;  
e) Class E – Water suitable for irrigation and agricultural activities; and  
f) Class F – Water with minimum quality but does not fall into categories A to E.  
4.2 Specific requirements  
The ambient water  shall comply with the requirements given in Table 1 when tested in accordance with the test 
methods specified  therein.   
©RSB 2023  - All rights reserved                  6 
  
 
Table 1 — Specific requirements for ambient water  
S/N Parameter  Requirement  Test 
method  A B C D E F 
1.  Color, Pt Co mg/l, max.  20 - - 100 - - RS ISO 
7887  
2.  Electrical conductivity, µS/cm, 
max.  800 800 1000  1000  1000  2000  RS ISO 
7888  
3.  Turbidity, NTU, max.  5 - - - - - ISO 7027 -
1 
4.  Total suspended solids, mg/l, 
max.  25 - 40 1500  2100  - RS ISO 
11923  
5.  Total hardness (as CaCO 3), 
mg/l 250 – 
600 -  - - - - RS ISO 
6059  
6.  pH 5.5 – 
8.5 5.5  – 
9.0 5.5  – 
8.5 5.5  – 
9.0 5.5  – 
8.5 5.5 – 
9.0 RS ISO 
10523  
7.  Dissolved Oxygen at 2 5 ⁰C, 
mg/l, min.  6 5 5 4 3 3 ISO 5814  
8.  Biological oxygen demand 
(BOD 5) at 25 ⁰C, mg/l, max.  3 4 4 5 12 15 RS ISO 
5815 -2 
9.  Chemical oxygen demand 
(COD), mg/l, max.  10 10 15 30 - 40 RS ISO 
6060  
10.  Nitrogen, Nitrates, mg/l, max.  10 10 10 10 - 10 RS ISO 
10304 -1 
11.  Nitrogen, 
ammonia, 
mg/l pH<7.5  - - 0.94 - - 9.1 RS ISO 
11732  7.5≤pH>8.5 - - 0.59 - - 4.9 
pH≥8.5 - - 0.22 - - 1.6 
12.  Phosphates, mg/l, max.  0.7 0.7 0.4 0.7 - - RS ISO 
15681 -1 
or RS ISO 
15681 -2 
13.  Chlorides, mg/l, max.  250 - - 250 600 - RS ISO 
9297 
14.  Cyanides,, mg/l, max.  0.05 0.05 0.05 0.05 0.05 0.05 ISO 6703 -
3 
15.  Fluorides, mg/l, max.  1.5 - - 250 600 - ISO 
10359 -2 
16.  Sulphates, mg/l, max.  250 - - 250 600 - RS ISO 
22743  
17.  Total cadmium, µg/l, max.  5 - 5 5 - 5 RS ISO 
5961  
18.  Total chromium, µg/l, max.  50 - 20 50 - 50 RS ISO 
9174  
19.  Total copper, µg/l, max.  - - 100 - - 100 RS ISO 
8288  
20.  Total iron, µg/l. 300 – 
1000  - - 2000  - - RS ISO 
6332  
21.  Total 
lead, µg/l, 
max.  Hardness <120  
50 - 2 
50 - - RS ISO 
8288  120≤hardness<180  3 
Hardness ≥180 4 Formatted:  German  (Switzerland)DRS 564: 2023  
7                ©RSB 2023  - All rights reserved  
 22.  Total manganese, µg/l, max.  1000  100 1000  1000  1000  1000  RS ISO 
6333  
23.  Total mercury, µg/l, max.  1 1 1 1 2 2 RS ISO 
12846  
24.  Total nickel, µg/l, max.  70 100 100 100 200 100 RS ISO 
8288  
25.  Total selenium, µg/l, max.  10 10 5 10 - - RS 
ISO/TS 
17379 -2 
26.  Total zinc, µg/l, max.  1000  - 1000  1000  2000  24000  RS ISO 
8288  
27.  Total boron, µg/l, max.  - - - - 1 - ISO 9390  
28.  Total arsenic, µg/l, max.  50 50 50 50 50 50 RS ISO 
17378 -2 
29.  Total aluminium, µg/l, max.  200 - - - 5000  5000  RS ISO 
12020  
30.  Phenolic compounds, µg/l, max.  2 5 2 5 5 5 RS ISO 
8165 -1  
RS ISO 
8165 -2 
31.  Oil/Grease, µg/l, max.  100 - 100 100 - 300 RS ISO 
9377 -2 
32.  Anionic surfactants as MBAS, 
µg/l, max.  1000  1000  1000  1000  1000  1000  ISO 
16265  
33.  Pesticides, µg/l, max.  
RS ISO 
15089  Aldrin/Dieldrin  0.03 - - - - - 
Chlordane (total)  0.3 - - - - - 
2,4- Dichlorophenoxyacetic acid  30 - - - - - 
DDT (total)  1 - - - - - 
Heptachlor and Heptachlor 
Epoxide  0.03 - - - - - 
Hexachlorobenzene  1 - - - - - 
Lindane BHC  2 - - - - - 
Methoxychlor  20 - - - - - 
MCPA, µg/l, max.  2 - - 20 - - 
Pendimethalin, µg/l, max.  2 - - 20 - - 
34.  Total coliform, MPN/100ml, 
max.  10000  10000  - 10000  - - RS ISO 
9308 -1 
RS ISO 
9308 -2 
35.  Faecal coliforms, MPN/100ml  500 – 
1000  500 – 
1000  - - - - RS ISO 
4831  
 
 
5 Ambient water quality guidelines an d monitoring  
5.1 Ambient water quality guidelines  
5.1.1  The competent authority shall establish the ambient Water quality guidelines for the protection of 
aquatic life, wildlife, agriculture, drinking water sources and recreation.  
5.1.2  The ambient water quality  guidelines shall be used in order to:  Formatted:  German  (Switzerland) 
©RSB 2023  - All rights reserved                  8 
 a) protect aquatic life, wildlife and their habitats;  
b) protect water values, including: drinking water, public supply, and food processing ; agriculture (livestock 
watering and irrigation); and recreation;  
c) provide the basis for the evaluation and ambient water quality and environmental impact assessments to 
inform resource management decisions (e.g., wastewater discharge limits:  
d) provide the basis for water quality objectives; and  
e) report to the public on the state of wat er quality and promote water stewardship.  
5.2 Ambient water quality monitoring  
Monitoring programme shall be carefully designed answer specific questions. For example, a programme 
designed to answer questions about ambient water quality status and trends diffe r from one designed to answer 
questions about extent and scale of chemical spill.  Ambient water quality activities shall be undertaken for such 
purposes as:  
a) Classification of water body . The water quality is monitored  quarterly for a period of one year. Among 
other factors, e.g.,  existing use and social acceptability, the result of analyses  are taken into account in 
deciding the appropriate  classification of a water body or section of a water body.  
b) Trend monitoring to check if a water body is meetin g its designated use . The water quality is monitored 
at regular  frequency to check if the water body is meeting the guideline  values for its classification. The 
results are used as basis for  decision -making, e.g., whether to institute management  interventi ons to 
improve water quality, or to reclassify a water  body, etc.  
c) Designation of Non -Attainment Areas . Designation of Non -Attainment Areas. A water body or portions 
of a water body may be identified as NAA for parameters  whose guideline values are not bein g met. This 
is based on:  
1) ten monthly sampling in a period of one year within the last two years, or  
2) quarterly sampling within the last two years (except for parameters requiring more frequent sampling 
based on water quality standard s). 
d) Monitoring for ECC compliance . If required in the ECC, the quality of a water body is monitored to ensure 
that a project or undertaking within or near a water body is not affecting the water quality.  
e) Monitoring to identify causes and sources of water -related problems . In cas es of occurrence of water -
related problems, e.g., disease epidemic, fish kills, red tide, etc., water quality monitoring is undertaken to 
identify specific problem pollutants and sources, and used as basis for identification of intervention and 
management strategies.  
f) Monitoring for baseline data and scientific studies.  Specific water quality parameters are analyzed for 
specified period of time to serve as baseline data or for certain studies.  
g) Monitoring for Other Purposes.  Monitoring for purposes other than  those mentioned above.  DRS 564: 2023  
9                ©RSB 2023  - All rights reserved  
 5.3 Water quality parameters  of measurement, timing and frequency  for monitoring  
5.3.1  The parameters to be  monitored  shall be specified. Choose the  parameters according to the objective 
of monitoring. For purposes of  classification for instance, the classification guidelines recommend  minimum test 
parameters for rivers, lakes and coastal and offshore  waters considering the beneficial uses.  The list  of water 
quality  parameters  for monitoring  are given in annex A . 
5.3.2  The monitoring plan sh all describe the intended timing and frequency of  monitoring. The frequency of 
monitoring would depend on the  monitoring objective. The timing should consider the effect of temporal  
variations on water quality.  
5.3.3  The sampling plan  should describe how often sample will be taken and at what times of the year as 
water quality changes with the seasons. Except as needed for special studies, it is not advisable to take samples 
when it is raining, within 24 hours after a heavy downpour or  when the  water level is at high stage. In these 
conditions, the water sample is not representative.  
5.3.4  The recommended parameters, frequency and duration of sampling  according to the objective of 
monitoring are shown in Table 2. 
Table 2 — Recommended parameters, frequency and duration of sampling  
S/N Objective of 
monitoring  Parameters  Sampling frequency (minimum)  Minimum duration 
of monitoring  
i.  Classification  Primary parameters  Quarterly 1 1 year  
ii.  Reclassification 2 Primary  10 monthly sampling in a period of 
one year  3 consecutive years  
Secondary 3 Quarterly  3 consecutive years 4 
iii.  Trend monitoring  Primary  10 monthly sampling in a period of 
one year  3 consecutive years 5 
Secondary  Quarterly (every 3 months)  3 consecutive years  
iv.  Designation of  
Non-Attainment  
Areas (NAA)  All relevant  
parameters  (a) ten monthly sampling in a 
period of one year within the last 
two years,  
or (b) quarterly sampling within 
the last two years (except for 
parameters  requiring more 
frequent sampling based on the 
water quality  standards)6 year for monthly 
monitoring; 2 years 
for quarterly 
monitoring  
v.  Monitoring for  ECC 
compliance  Selected/specific to  
project or site  
condition;  
parameters  
prescribed in the  
EMoP or ECC  As prescribed in the  EMoP or in 
the ECC  As prescribed  
in the EMoP  
or in the ECC  
vi.  Monitoring to  identify 
causes  and sources 
of water -related  
problems  Selected /specific to  
situation  High, will depend on  impact area 
and parameter  very short  
(days -weeks)  
Monitoring for 1 year  Primary  Once a month for 12 months  1 year  Commented [EU1]: To be removed   
©RSB 2023  - All rights reserved                  10 
 vii.  baseline data  and 
scientific  studies  Secondary  Once a month for 12 months  1 year  
viii.  Other purposes  Selected based  
on objective  As necessary depending  
on objective  < 1 year  
1 Minimum of three (3) sampling sites per water body classification.  
2 It is not not necessary to undertake separate monitoring if trend monitoring is being conducted. Data from  
trend monitoring may be used.  
3 Important secondary parameters specific to the  water body as identified by the EMB -RO or the agency  
conducting the monitoring  
4 Data from trend monitoring may be used.  
5 Monitoring may be continued afterward or may be resumed later as necessary.  
6 Data from trend monitoring may be used  
7 Selected para meters specific to the water body as identified by the EMB -RO or monitoring agency  
6 Sampling  
6.1 Sampling programmes and techniques  
The sampling programmes and techniques for ambient water shall be done in accordance with ISO 5667 -1. 
 
 
 DRS 564: 2023  
11                ©RSB 2023  - All rights reserved  
 Annex  A 
(informative)  
 
Ambient water quality parameters of measurement  
Water quality parameter for ambient water monitoring are given in the following table:  
NOTE  The competent authority may add or reduce the number of parameters when it deems necessary.  
Table A1 – Parameters for ambient water monitoring  
Category  Parameters  
Primary parameters  Biochemical oxygen demand (BOD)  
Chlorides  
Color (true)  
Dissolved oxygen (DO)  
Faecal coliforms  
pH 
Phosphates  
Temperature  
Total suspended solids  
Secondary parameters  Ammonia -Nitrogen (NH 3-N) 
Barium (Ba)  
Iron (Fe)  
Sulfate (SO 42-) 
Secondary parameters – Toxic metals  Arsenic (As)  
Cadmium (Cd)  
Hexavalent chromium (Cr6+) 
Copper (Cu)  
Lead (Pb)  
Mercury (Hg)  
Nickel (Ni)  
Secondary parameters – Organics  Animal -Vegetable fats and oils  
Benzene  
Toluene  
Ethylbenzene  
Xylene  
Cyanides  
 
 
   
©RSB 2023  - All rights reserved                  12 
 Bibliography  
[1] Sri Lanka , National Environmental (Ambient water quality) Regulations,  No 01 of 2019. 
[2] Philippine, Environmental Management Bureau – Department of Environment and Natural Resources , 
Water Quality Monitoring Manual  — Volume I: Manual on ambient water quality monitoring, February 2008.  
[3] United Nations Environment Programme , Progress on ambient water qu ality — Global indicator 6.3.2 
Updates and acceleration needs, 2021  
 
 DRS 564: 2023  
 
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