Table 5.

Overview of the optical and fibre optic sensing for Color, COD and BOD detection.

Parameter	Material	Optical Range (nm)	Detection Range (mg/L)	Sensing Method	Response Time	Advantageous/Limitation	Application	Ref.
Color	Direct determination	514.5	1000	Optical (Absorption-Based)	5 min	Sample handling	Dyed fibres	[76]
Color	Leather Dye Mixture Color (Red-Blue-Yellow)	400 to 900	Differentiate mixture of color, errors5.6 to10.7 and 6.9 to12.5%	Optical (Absorption-Based)	Once the PLSR method is optimized, new samples can be determined.	Sample handling	Leather dye detection	[77]
Color	Indigo Solution	635	800 to 12000, errors 0.5%	Optical (Absorption-Based)	15 min	Real time monitoring	Denim yarn	[78]
Color	Red, Amber, Blue solution	300 to 900	36 to1000, errors 1%	FOS	10 spectra were taken and averaged	Sample handling	Textile industry-dye bath	[79]
COD	Direct determination	254 & 356	0 to360 ± 1.8	Optical (Absorption-Based)	∼2 min	Sample handling	Printing and dyeing wastewater	[80]
COD	Direct determination	excitation wavelengths from 250 to 600	13 to 456 ± 6%	Optical (Synchronous Fluorescence)	Standard laboratory device.	Sample handling	Waste water from urban and non-urban area	[3]
COD	Phthalatehydrogen potassium for oxidation	near-infrared (NIR) transmission & ultraviolet absorbance (254)	5 to 400 ± 2%	Optical (Absorption-Based)	---	Real time monitoring	Organic pollutant	[24]
COD	Potassium hydrogen phthalate solution	200 to 720	30 to 1000 ± 1%	Optical	5 min	Real time monitoring	Lakes, river or waste water	[81]
COD	Direct determination	UV-220 & 254 emission spectra 300 to 550	1.6 to 20.6 ± 3%	Optical	--	Real time monitoring	Urban river water	[82]
COD	Direct determination	258 to 380& UV	0 to 350 ± 6%	FOS	62 s	Real time monitoring	Wastewater quality monitoring	[83]
BOD	Direct determination	220 to 1,100; excitation/emission 280/350	0 to 400	Optical (Absorption and Fluorescence Technique)	Standard laboratory device.	Sample handling	Sewage sample	[84]
BOD	Direct determination	190 to 900	100 to 10,000	Optical	Standard laboratory device.	Sample handling	Dirty water, slurry water	[25]
BOD	Direct determination	Excitation 250 to 600 nm	5.2 to 208 ± 8%	Optical (Synchronous Fluorescence)	Standard laboratory device.	Sample handling	Waste water from urban and non-urban area	[3]
BOD	Direct Determination	220 to 1,100 ;excitation λ 250 to 400 nm; emission λ 300 to 550 nm	0.5 to 25.4 ± 3%	Optical (Absorption and Flurescence)	Standard laboratory device	Sample handling	Urban river water	[82]
BOD	Direct determination	254 nm and fluorescence intensity 270 ∼ 300, 310 ∼ 370, 370 ∼ 400 & 400 ∼ 530	Waste water = 6.5 to 139.9 ± 10%; River water = 1.3 to 1.9 ± 22%	Optical (Absorption and Synchronous Flurescence)	Predict BOD by using multiple regression analysis	Sample handling	River water samples wastewater treatment plant effluent	[28]
BOD	Tris(4,7-diphenyl-l,lOphenanthroline) ruthenium(II) perchlorate; Trichosporon cufaneum	480, excitation 610 nm.	3 to 110 ± 4%	FOS	3–10 min	Rapid feedback signal, very low costs	Sewage plant effluent and municipal sewage	[85]
BOD	Pseudomonas putida	Used current	1 to 10 ± 20%	FOS (Fluorescenc-Based)	15 min	Long-term stability, no calibration drift occurs, not affected by heavy metal ions and chlorine concentration	River Water	[86]
BOD	Ru(I1) polypyridyl complex	Red-excitation, Blue-emmision	--	FOS	--	Real time monitoring	Waste water	[87]
BOD	Tris(4,7-diphenyl-1, 10-phenanthroline) ruthenium(II) dye;B. subtilis, &activated sludge	Four LED blue light (460 nm)	25 to 60 ± 14%	FOS (Fluorescenc-Based)	15–30 min (by batch)	Sample handling	GGA, domestic and synthetic WW, OECD	[88]
BOD	4,7-diphenyl-1,10-phenanthroline Ru(dpp)32+; B. licheniformis, D. marisand M.marinus	Blue LED (465 nm)	0.2 to 40	FOS (Fluorescenc-Based)	3.2 min	without dramatically affected by sodium chloride	Seawater	[89]