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Document ID ca-gcdwq-2023-01-20-5 Title Guidelines for Canadian drinking water quality – Malathion: Analytical and treatment considerations URL https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-supporting-documents-malathion/analytical-treatment-considerations.html Jurisdiction /ca Subdomain(s) Drinking water, Analytical methods, Treatment process Language en Status completed Analyzed at 2026-03-18 15:11:33.776979+00:00 Relevance Analytical methods and treatment guidelines for malathion in drinking water.

14 Qualitative 38 Quantitative 33 Definitions

Q Qualitative Requirements (14)

Req ID	Category	Intent	Legal Status	Name	Subdomain(s)	Context	Conditions	Confidence
#Q001	monitoring	operational	recommended	Laboratory Sampling Requirements Discussion	drinking water	Drinking water utilities should discuss sampling requirements with the accredited laboratory conducting the analysis to ensure that quality control procedures are met and that MRLs are low enough to ensure accurate monitoring at concentrations below the MAC.		high
#Q002	monitoring	operational	guideline	Sample Quenching	drinking water	It is important to note that quenching is critical if an oxidant is present in samples in order to reduce additional degradation of malathion.	If an oxidant is present in samples	high
#Q003	monitoring	operational	recommended	Sample Cooling and Rapid Analysis	drinking water	As such, cooling of the samples and rapid analysis are recommended.		high
#Q004	treatment	treatment	recommended	Bench or Pilot Testing for Municipal Scale	drinking water	Bench or pilot testing is recommended to ensure the source water can be successfully treated and optimal process design is established.	When selecting an appropriate treatment process for a specific water supply	high
#Q005	treatment	health	recommended	Primary and Secondary Objectives of Treatment	drinking water	The primary objective should be removal of the pesticide with the secondary objective being the minimization of by-product formation.	When using oxidation or advanced oxidation processes (AOP) for pesticide removal	high
#Q006	treatment	health	recommended	Consideration of Disinfection By-Products	drinking water	In addition, water utilities should consider the potential for the formation of disinfection by-products depending on the oxidant selected and the source water quality.	When using oxidation or advanced oxidation processes	high
#Q007	treatment	treatment	recommended	Activated Carbon Adsorption Testing	drinking water	Since the capacity of activated carbon can be affected by many factors, including the compound's ionic character and the solution pH, appropriate testing (for example, jar tests, rapid small-scale column tests) should be conducted to confirm removal.	When using activated carbon adsorption	high
#Q008	treatment	treatment	guidance	Membrane Filtration Testing	drinking water	It is important to perform appropriate testing prior to full-scale implementation with membrane and source water under the proposed operating conditions to ensure that adequate malathion removal is occurring.	Prior to full-scale implementation of membrane filtration	high
#Q009	treatment	treatment	mandatory	Advanced Oxidation Process Testing	drinking water	Prior to full-scale application, appropriate pilot-scale or bench-scale testing would need to be conducted evaluating malathion removal as well as the degradation products.	Prior to full-scale application of advanced oxidation processes	high
#Q010	monitoring	operational	recommended	Source Water Testing Prior to Treatment Unit Installation	drinking water	Before a treatment unit is installed, the water should be tested to determine the general water chemistry and malathion concentration in the source water.	Before a residential treatment unit is installed	high
#Q011	monitoring	operational	recommended	Verification Sampling for Treatment Units	drinking water	To verify that a treatment unit is effective, water entering and leaving the treatment unit should be sampled periodically and submitted to an accredited laboratory for analysis.	To verify residential scale treatment unit effectiveness	high
#Q012	operational	operational	recommended	Treatment Unit Component Longevity and Servicing	drinking water	Consumers should verify the expected longevity of the components in the treatment unit according to the manufacturer's recommendations and service it when required.		high
#Q013	treatment	health	recommended	Treatment Unit Certification Recommendation	drinking water	Health Canada does not recommend specific brands of drinking water treatment units, but it strongly recommends that consumers use units that have been certified by an accredited certification body as meeting the appropriate NSF International Standard/American National Standard (NSF/ANSI) for drinking water treatment units.		high
#Q014	design	operational	recommended	Reverse Osmosis Point of Use Installation	drinking water	Water that has been treated using RO may be corrosive to internal plumbing components. Therefore, these units should be installed only at the point of use.	When using residential reverse osmosis units	high

P Quantitative Requirements (38)

Req ID	Category	Intent	Legal Status	Name	Subdomain(s)	Limit Type	Limit Value	Context	Conditions	Confidence
#P001	design	treatment	guidance	adsorption capacity constant (Freundlich coefficient)	drinking water	unknown	> 200 µg/g(L/µg)1/n	Pesticides with an adsorption capacity constant greater than 200 µg/g(L/µg)1/n are considered to be amenable to removal by carbon adsorption.	When evaluating amenability to removal by carbon adsorption	high
#P002	design	treatment	guidance	molecular weight cut-off (MWCO)	drinking water	unknown	200-400 Da	Based on the molecular weight of malathion (217 Da), membranes with a MWCO varying between 200 and 400 Da are considered appropriate for malathion.	For the removal of malathion using nanofiltration (NF) or reverse osmosis (RO) membranes	high
#P003	chemical	reporting	guideline	EPA 527 Rev. 1.0 MDL	drinking water	requirement	0.057 µg/L	Standardized method detection limit for analysis of malathion in water	Capillary column gas chromatography/mass spectrometry (GC/MS)	high
#P004	chemical	reporting	guideline	EPA 1699 MDL	drinking water	requirement	0.0003 µg/L	Standardized method detection limit for analysis of malathion in water	High-resolution GC/MS; Equivalent to 296 pg/L	high
#P005	chemical	reporting	guideline	EPA 8141B Rev. 2 MDL	drinking water	requirement	5.5 µg/L	Standardized method detection limit for analysis of malathion in water	Gas chromatography with flame photometric detector (GC/FPD)	high
#P006	chemical	reporting	guideline	EPA 8270D Rev. 4.0 Estimated Quantitation Limit	drinking water	requirement	50 µg/L	Standardized estimated quantitation limit for analysis of malathion in water	GC/MS	high
#P007	chemical	reporting	guideline	USGS O-1104 MDL	drinking water	requirement	0.01 µg/L	Standardized method detection limit for analysis of malathion in water	GC/FPD; MDL is estimated	high
#P008	chemical	reporting	guideline	USGS O-1126-95 MDL	drinking water	requirement	0.005 µg/L	Standardized method detection limit for analysis of malathion in water	GC/MS	high
#P009	chemical	reporting	guideline	USGS O-1402-01 MDL	drinking water	requirement	0.005 µg/L	Standardized method detection limit for analysis of malathion in water	GC/FPD	high
#P010	chemical	reporting	guideline	USGS O-3104 MDL	drinking water	requirement	0.01 µg/L	Standardized method detection limit for analysis of malathion in water	GC/FPD; MDL is estimated	high
#P011	chemical	reporting	guideline	USGS O-3402-03 MDL	drinking water	requirement	0.0040 µg/L	Standardized method detection limit for analysis of malathion in water	Gas chromatography (unspecified detector)	high
#P012	operational	operational	guidance	Malathion half-life at pH 8.0	drinking water	OG	0.2 weeks	Degradation of malathion in water is pH dependent and it degrades quickly in water with pH > 7.0.	pH 8.0	high
#P013	operational	operational	guidance	Malathion half-life at pH 6.0	drinking water	OG	21 weeks	Degradation of malathion in water is pH dependent.	pH 6.0	high
#P014	chemical	reporting	guidance	GC/MS Method Reporting Limit (MRL) range (Canadian accredited laboratories)	drinking water	requirement	0.02 to 5 μg/L	A number of accredited laboratories in Canada were contacted to determine MDLs and MRLs for malathion analysis.	Gas Chromatography with Mass Spectrometry Detection (GC/MS)	high
#P015	chemical	reporting	guidance	Provincial and territorial MDL/MRL range	drinking water	requirement	0.0001 to 15 μg/L	The MDLs or MRLs from provincial and territorial data.	Refer to the section on exposure	high
#P016	chemical	operational	guidance	Hypochlorous acid (HOCl) dissociation constant (pKa)	drinking water	unknown	7.6 pKa	HOCl is a weak acid that dissociates to produce hypochlorite ion (OCl-).	at 20°C	high
#P017	operational	treatment	guidance	Alkaline hydrolysis degradation efficiency	drinking water	treatment_goal	93 %	Above pH 8.0, alkaline hydrolysis was the primary degradation pathway for malathion.	pH > 8.0	high
#P018	operational	treatment	guidance	Chlorination removal efficiency	drinking water	treatment_goal	> 50 %	Removal of malathion using chlorination at typical drinking water disinfection doses	At pH levels of 6.6 and 8.6; 23 ± 1°C	high
#P019	operational	treatment	guidance	Ozonation removal efficiency (pH 8.6)	drinking water	treatment_goal	20-50 %	Removal of malathion using ozonation process at alkaline pH	pH 8.6	high
#P020	design	treatment	guidance	H2O2/O3 dosage ratio for advanced oxidation	drinking water	OG	0.4 g H2O2/g O3	Constant ratio of hydrogen peroxide to ozone for efficient malathion degradation (>99%)	O3/H2O2 process	high
#P021	operational	operational	guidance	Degradation rate constant ratio (malathion to malaoxon)	drinking water	OG	4.3-5.6 ratio	Ratio of degradation rate constant of malathion (kmalathion) to malaoxon (kmalaoxon)	For several oxidation and AOPs reactions	high
#P022	operational	treatment	guidance	Low-reactivity oxidant removal efficiency	drinking water	treatment_goal	< 20 %	Oxidants such as monochloramine (NH2Cl), chlorine dioxide (ClO2), permanganate (MnO4), hydrogen peroxide (H2O2) and direct ultraviolet (UV) photolysis at 254 nm achieved less than 20% removal of malathion.	Typical drinking water disinfection doses; UV at 254 nm	high
#P023	operational	treatment	guidance	UV oxidation degradation rate constant (malathion)	drinking water	OG	6.5 x 104 cm2/mJ	Degradation rate constant measured in UV oxidation process.	UV oxidation process	high
#P024	operational	treatment	guidance	UV oxidation degradation rate constant (malaoxon)	drinking water	OG	1.4 x 104 cm2/mJ	Degradation rate constant measured in UV oxidation process for byproduct malaoxon.	UV oxidation process	high
#P025	operational	treatment	guidance	UV/H2O2 oxidation degradation rate constant (malathion)	drinking water	OG	133.6 x 104 cm2/mJ	Degradation rate constant measured in UV/H2O2 advanced oxidation process.	UV/H2O2 oxidation process	high
#P026	operational	treatment	guidance	UV/H2O2 oxidation degradation rate constant (malaoxon)	drinking water	OG	23.9 x 104 cm2/mJ	Degradation rate constant measured in UV/H2O2 advanced oxidation process for byproduct malaoxon.	UV/H2O2 oxidation process	high
#P027	physical	treatment	guidance	Malathion Molecular Weight	drinking water	unknown	217 Da	Based on the molecular weight of malathion (217 Da), membranes with a MWCO varying between 200 and 400 Da are considered appropriate for malathion.		high
#P028	operational	treatment	guidance	Malathion removal via polyaluminum chloride coagulation	drinking water	treatment_goal	0 %	A bench-scale study evaluated chemical coagulation and sedimentation treatment technologies... results showed no removal (see Table 5).	River water at 20 °C; 1L; final pH of 7.0; Dosed with 1.0 and 1.4 mg/L coagulant	high
#P029	operational	treatment	guidance	Malathion removal via PAC (10 mg/L)	drinking water	treatment_goal	76 %	Bench-scale study conducted to determine the adsorption of malathion to PAC... with a PAC dose of 10 mg/L	River water; 10-minute contact time; pH 7.0	high
#P030	operational	treatment	guidance	Malaoxon removal via PAC (10 mg/L)	drinking water	treatment_goal	69 %	Bench-scale study conducted to determine the adsorption of malaoxon to PAC... with a PAC dose of 10 mg/L	River water; 10-minute contact time; pH 7.0	high
#P031	operational	treatment	guideline	Removal of malathion through coagulation, flocculation, filtration	drinking water	treatment_goal	62.21 ± 0.01 %	Cumulative removal of malathion through physical-chemical treatment steps prior to chlorination.	Dosed with 20 mL aluminum sulphate at 1% (w/v); pH 10.5; Ultra-pure water	high
#P032	operational	treatment	guideline	Removal of malathion through chlorination (cumulative)	drinking water	treatment_goal	73.2 ± 0.2 %	Total removal after coagulation, flocculation, filtration followed by chlorination.	Chlorine dose = 5 mg/L; pH 10.5	high
#P033	operational	treatment	guidance	Malathion removal range via CSAC GAC	drinking water	treatment_goal	28.6 to 82.9 %	Removal efficiency of malathion using coconut shell activated carbon at varying EBCT.	EBCT from 2.95 to 19.6 min; Temperature = 30°C	high
#P034	operational	treatment	guidance	Malathion removal range via PSAC GAC	drinking water	treatment_goal	18.6 to 71.4 %	Removal efficiency of malathion using palm shell activated carbon at varying EBCT.	EBCT from 2.95 to 19.6 min; Temperature = 30°C	high
#P035	operational	treatment	guidance	Malathion rejection via NS-100 RO membrane	drinking water	treatment_goal	99.65 %	Rejection efficiency of malathion using cross-linked polyethylenimine membrane.	Pressure = 40.8 atm; Room temperature; Demineralized water	high
#P036	chemical	treatment	guidance	Hypochlorous acid (HOCl) oxidation rate of malathion	drinking water	OG	1.72 (± 0.36) x 106 M-1 H-1	Specific oxidation rate of malathion by HOCl in deionized water.	pH 6.5; 25 ± 1°C; 0.5 μM malathion	high
#P037	chemical	treatment	guidance	Hypochlorite ion (OCl-) oxidation rate of malathion	drinking water	OG	382 (± 0.26) M-1 H-1	Specific oxidation rate of malathion by OCl- in deionized water.	pH 6.5; 25 ± 1°C; 0.5 μM malathion	high
#P038	operational	treatment	guidance	Gross removal range of malathion and malaoxon via PAC/coagulation	drinking water	treatment_goal	23.8 to 42.5 %	Total gross removal efficiency through a treatment train involving PAC-assisted coagulation-sedimentation-filtration and chlorination.	Pre-chlorination doses from 0 to 3 mg/L; 10 mg/L PAC; 120 μM Al2SO4; Post-chlorination 1 mg/L	high

D Definitions (33)

Req ID	Name	Context	Confidence
#D001	GC/MS	Gas Chromatography with Mass Spectrometry Detection	high
#D002	RO	reverse osmosis	high
#D003	AOP	advanced oxidation processes	high
#D004	PAC	powdered activated carbon	high
#D005	GAC	granular activated carbon	high
#D006	NOM	natural organic matter	high
#D007	EBCT	empty bed contact time	high
#D008	PSAC	palm shell activated carbon	high
#D009	CSAC	coconut shell activated carbon	high
#D010	NF	nanofiltration	high
#D011	MWCO	molecular weight cut-off	high
#D012	UV	ultraviolet	high
#D013	quantum yield	a number of moles of the reactant being degraded per mole of photons absorbed	high
#D014	TOC	total organic carbon	high
#D015	NSF/ANSI	NSF International Standard/American National Standard	high
#D016	pKa	dissociation constant	high
#D017	HOCl	hypochlorous acid	high
#D018	OCl-	hypochlorite ion	high
#D019	NH2Cl	monochloramine	high
#D020	NHCl2	dichloramine	high
#D021	MDL	method detection limit	high
#D022	GC/FPD	Gas chromatography with flame photometric detector	high
#D023	DOC	dissolved organic carbon	high
#D024	PAC-CSF	powdered activated carbon assisted coagulation-sedimentation-filtration	high
#D025	Cl2	chlorine	high
#D026	O3	ozone	high
#D027	ClO2	chlorine dioxide	high
#D028	MnO4	permanganate	high
#D029	H2O2	hydrogen peroxide	high
#D030	*OH	hydroxyl radical	high
#D031	Conventional filtration	chemical coagulation, clarification and rapid sand filtration	high
#D032	ozonolysis	direct ozone reaction	high
#D033	Jw	Pure water flux	high