These waters shall be free from floating, suspended and settleable
solids in concentrations or combinations that would impair any use assigned to this class, that would cause aesthetically objectionable conditions, or that would impair the benthic biota or degrade the chemical composition of the bottom.").
Once collected, the water is tested for iron, manganese, settleable
and suspended solids, turbidity, and pH.
A one-way analysis of variance (ANOVA, [alpha] = 0.05) was used to identify significant differences between treatments in water quality variables (temperature, DO, pH, salinity, TAN, nitrite-nitrogen, nitrate-nitrogen, silicate, orthophosphate, alkalinity, and settleable
solids), bacterial densities (Vibrio, THB, and TAB), production variables (final weight, SGR, survival, yield, and FCR) and phytoplankton densities (Bacillariophyceae, Cyanophyceae, Chlorophyceae, Haptophyceae, Dinophyceae, and Euglenophyceae).
Range of tannery effluent quality parameters Parameters Range pH (unsettled effluent) 7.3-10 BO[D.sub.5], mg/L (30 min settling) 840-18,620 COD, mg/L (30 min settling) 1320-54,000 Suspended solids, mg/L (30 min settling) 220-1610 Settleable
solids, mg/L (30 min settling) 11-40 Sulphate, mg/L (unsettled effluent) 800-6480 Sulphide, mg/L (at 0 time settling) 800-6480 Chromium, mg/L (unsettled effluent) 41-133 Table 2.
The variation in the average values of physical and chemical characteristics of the dairy effluent studied soon after all of the samples were collected was: pH (1.0-5.4), turbity (267-1000NTU), COD (2060-5249mg [L.sup.-1]), total solids (TS) (1965-3723mg L-1), total volatile solids (TVS) (1560-3434mg L-1), total fixed solids (TFS) (405-592mg L-1), total dissolved solids (TDS) (1521-3083mg L-1), volatile dissolved solids (VDS) (1198-2843mg L-1), fixed dissolved solids (FDS) (240-492mg L-1), total suspended solids (TSS) (444-758mg L-1), volatile suspended solids (VSS) (397-658mg [L.sup.-1]), fixed suspended solids (FSS) (47-100mg [L.sup.-1]) and settleable
solids (SS) (0.4-0.5mL [L.sup.-1]).
The water transparency and the settleable
solids were measured with a Secchi disc and cone Inhoff, respectively.
Parameter Unit Values pH pH unit 3.30 [+ or -] 0.11 Conductivity [micro]S 1.066 [+ or -] 62.43 [cm.sup.-1] [BOD.sub.5] mg [L.sup.-3] 4.670 [+ or -] 150.44 COD mg [L.sup.-3] 11.817 [+ or -] 1.228 OD mg [L.sup.-3] 4.08 [+ or -] 0.46 Settleable
solids mg [L.sup.-3] 715 [+ or -] 21 Total fixed solids mg [L.sup.-3] 458 [+ or -] 29 Total volatile solids mg [L.sup.-3] 5.718 [+ or -] 154 Turbidity ntu 1.347 [+ or -] 194 Color mg Pt [L.sup.-1] 14.900 [+ or -] 2.638 Temperature [degrees]C 24.3 [+ or -] 0.6 Dissolved iron mg [L.sup.-1] 0.64 [+ or -] 0.09 Table 3.
It is likewise considered good practice either to convert other soluble pollutants to settleable
biosolids or to flocculate them chemically.
The county has been involved long-term in upgrading the small sewage system and is currently replacing the clarigester which uses a series of settling tanks to separate floating and settleable
solids from waste.
In addition, several studies aimed to evaluate site-specificity, seasonality, and daily variability of settleable
Moilleron, "Priority pollutants in surface waters and settleable
particles within a densely urbanised area: case study of Paris (France)," Science of the Total Environment, vol.
While I don't have access to a full set of empirical information, I suspect that before Sackett, EPA may have over-relied on the power of its ability to issue unilateral orders that were not subject to pre-enforcement review, to the detriment perhaps of resolving settleable
cases through settlement.