Sludge Volume Index

	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	V	W	X	Y	AA	AB	AC	AD	AE	AF	AG	AH	AI	AJ	AK	AL	AM	AN	AO	AP	AQ	AR	AS
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2			Sludge Volume Index																							Sludge Density Index
3	SSV30	500	500	400	333	286	250	222	200	182	167	154	143	133	125	118	111	105	100					SSV30	500	0.20	0.25	0.30	0.35	0.40	0.45	0.50	0.55	0.60	0.65	0.70	0.75	0.80	0.85	0.90	0.95	1.00
4		475	475	380	317	271	238	211	190	173	158	146	136	127	119	112	106	100	95						475	0.21	0.26	0.32	0.37	0.42	0.47	0.53	0.58	0.63	0.68	0.74	0.79	0.84	0.89	0.95	1.00	1.05
5		450	450	360	300	257	225	200	180	164	150	138	129	120	113	106	100	95	90						450	0.22	0.28	0.33	0.39	0.44	0.50	0.56	0.61	0.67	0.72	0.78	0.83	0.89	0.94	1.00	1.06	1.11
6		425	425	340	283	243	213	189	170	155	142	131	121	113	106	100	94	89	85						425	0.24	0.29	0.35	0.41	0.47	0.53	0.59	0.65	0.71	0.76	0.82	0.88	0.94	1.00	1.06	1.12	1.18
7		400	400	320	267	229	200	178	160	145	133	123	114	107	100	94	89	84	80						400	0.25	0.31	0.38	0.44	0.50	0.56	0.63	0.69	0.75	0.81	0.88	0.94	1.00	1.06	1.13	1.19	1.25
8		375	375	300	250	214	188	167	150	136	125	115	107	100	94	88	83	79	75						375	0.27	0.33	0.40	0.47	0.53	0.60	0.67	0.73	0.80	0.87	0.93	1.00	1.07	1.13	1.20	1.27	1.33
9		350	350	280	233	200	175	156	140	127	117	108	100	93	88	82	78	74	70						350	0.29	0.36	0.43	0.50	0.57	0.64	0.71	0.79	0.86	0.93	1.00	1.07	1.14	1.21	1.29	1.36	1.43
10		325	325	260	217	186	163	144	130	118	108	100	93	87	81	76	72	68	65	Think of the MLSS as the "anchor". As sludge gets younger, it takes up more space and is less dense:					325	0.31	0.38	0.46	0.54	0.62	0.69	0.77	0.85	0.92	1.00	1.08	1.15	1.23	1.31	1.38	1.46	1.54
11		300	300	240	200	171	150	133	120	109	100	92	86	80	75	71	67	63	60						300	0.33	0.42	0.50	0.58	0.67	0.75	0.83	0.92	1.00	1.08	1.17	1.25	1.33	1.42	1.50	1.58	1.67
12		275	275	220	183	157	138	122	110	100	92	85	79	73	69	65	61	58	55						275	0.36	0.45	0.55	0.64	0.73	0.82	0.91	1.00	1.09	1.18	1.27	1.36	1.45	1.55	1.64	1.73	1.82
13		250	250	200	167	143	125	111	100	91	83	77	71	67	63	59	56	53	50						250	0.40	0.50	0.60	0.70	0.80	0.90	1.00	1.10	1.20	1.30	1.40	1.50	1.60	1.70	1.80	1.90	2.00
14		225	225	180	150	129	113	100	90	82	75	69	64	60	56	53	50	47	45						225	0.44	0.56	0.67	0.78	0.89	1.00	1.11	1.22	1.33	1.44	1.56	1.67	1.78	1.89	2.00	2.11	2.22
15		200	200	160	133	114	100	89	80	73	67	62	57	53	50	47	44	42	40	MLSS	SSV30	SVI	SDI		200	0.50	0.63	0.75	0.88	1.00	1.13	1.25	1.38	1.50	1.63	1.75	1.88	2.00	2.13	2.25	2.38	2.50
16		175	175	140	117	100	88	78	70	64	58	54	50	47	44	41	39	37	35	3000	300	100	1.00		175	0.57	0.71	0.86	1.00	1.14	1.29	1.43	1.57	1.71	1.86	2.00	2.14	2.29	2.43	2.57	2.71	2.86
17		150	150	120	100	86	75	67	60	55	50	46	43	40	38	35	33	32	30	3000	325	108	0.92		150	0.67	0.83	1.00	1.17	1.33	1.50	1.67	1.83	2.00	2.17	2.33	2.50	2.67	2.83	3.00	3.17	3.33
18		125	125	100	83	71	63	56	50	45	42	38	36	33	31	29	28	26	25	3000	350	117	0.86		125	0.80	1.00	1.20	1.40	1.60	1.80	2.00	2.20	2.40	2.60	2.80	3.00	3.20	3.40	3.60	3.80	4.00
19		100	100	80	67	57	50	44	40	36	33	31	29	27	25	24	22	21	20	3000	375	125	0.80		100	1.00	1.25	1.50	1.75	2.00	2.25	2.50	2.75	3.00	3.25	3.50	3.75	4.00	4.25	4.50	4.75	5.00
20			1,000	1,250	1,500	1,750	2,000	2,250	2,500	2,750	3,000	3,250	3,500	3,750	4,000	4,250	4,500	4,750	5,000							1,000	1,250	1,500	1,750	2,000	2,250	2,500	2,750	3,000	3,250	3,500	3,750	4,000	4,250	4,500	4,750	5,000
21			MLSS																							MLSS
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24			SVI (mL/g) =			SSV30 (mL/L)			x	1,000 (mg/g)																SDI (g/100mL) =			100 (mL)
25			SVI (mL/g) =			MLSS (mg/L)			x	1,000 (mg/g)																SDI (g/100mL) =			SVI (mL/g)
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27		The 1,000 here is multiplying by a conversion of 1,000 mg/g. The final SVI value is in the units of mL/g (not mg/L) which can be converted to mL/mL, which cancels itself. For pure water with a specific gravity of 1.0: 1 mL = 1 gram. Pure water in a settleometer will compress to 1 mL/g which equates to 1 mL/mL = 1. Secondary sludge typically has a specific gravity of 1.01 (1 percent or 1/100th heavier than water), so it settles (duh), but it won’t compact 100% to 1 mL/mL like pure water does. It should compact to (1 mL/mL) ÷ (1/100) = 100 mL/mL = 100. This says it takes up 100x the space of pure water because it’s fairly buoyant and is mostly water itself. Primary sludge with a specific gravity of 1.05 should compact to (1 mL/mL) ÷ (5/100) = 20x the space of water. Still buoyant, but definitely more dense than secondary sludge.																							There is a lesser used indicator of Sludge Density Index (SDI) that represents weight vs. volume and has an inverse relationship to SVI. Its formula is: SDI = 100 ÷ SVI with units resulting in grams per 100 mL. This equates to grams per 100 grams or just the decimal fraction of water's density. This is a ratio of compaction vs. expectation. A sludge that has an SSV30 of 250mL/L and a concentration of 3,000 mg/L will have an SDI of 1.20. This means it is 1.2x or 20% denser than normal. If normal specific gravity = 1.01, then it is possible our current specific gravity is actually 1.012. A more likely explanation is bug sizes are smaller (older sludge) or the water is less dense due to higher temperatures. This result of 1.2 grams per 100 mL also equates to 12,000 mg/L which makes sense if our MLSS of 3,000 compacts to 25% or 4x its volume.
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