Page 160 - Membranes for Industrial Wastewater Recovery and Re-Use

I 34 Membranes for Industrial Wastewater Recovery and Re-use

Table 3.20 Textile processing categories and effluent characteristics (EPA, 1978,1997)
Parameters Categoriesa
1 2 3 4 5 6 7
BOD/COD 0.2 0.29 0.3 5 0.54 0.35 0.3 0.31
BOD (mg/l) 6000 300 350 650 3 50 300 250
TSS (mgil) 8000 130 200 300 300 120 75
COD (mg/l) 30 000 1040 1000 1200 1000 1000 800
Oil and grease (mg/l) 5500 14 53 - ~
Total chrome (mg/l) 0.05 4 0.014 0.04 0.05 0.42 0.27
Phenol (mg/l) 1.5 0.5 0.04 0.24 0.13 0.12
Sulphide (mg/l) 0.2 0.1 8.0 3.0 0.2 0.14 0.09
Colour AD MI)^ 2000 1000 - 325 400 600 600
PH 8.0 7.0 10 10 8.0 8.0 11
Temperature ("C) 28 62 21 37 39 20 38
Water usage (l/kg)
Minimum 4 33 111 5 20 8 3
Median 12 - 284 113 83 47 100
Maximum 78 657 507 3 78 163 557
a Categories description: 1. raw wool scouring: 2. yarn and fabric manufacturing: 3, wool finishing: 4.
woven fabric finishing: 5, knitted fabric finishing: 6, carpet finishing: 7, stock and yarn dyeing and
finishing.
ADMI (American Dye Manufacturers Institute) colour values result from a special procedure for
determination of colour in dyeing wastewaters (Allen et al.. 1972; Little, 1978).

example, a woven cotton fabric finishing mill (Fig. 3.29) will typically
have processes for preparing the material (which will include some or all of the
processes of singeing, desizing, scouring/washing, mercerising and bleaching),
colouring it (dyeing and printing) and then fixing these colouring reagents
mechanically and/or chemically. The process can thus generate up to six
different liquid effluents which are conventionally combined to yield an effluent
quality similar to that listed under Category 4 in Table 3.20, and discharged to
sewer. However, since some components, and dyes in particular, are not readily
removed by conventional municipal wastewater treatment, which is based
largely on primary sedimentation followed by biological treatment, surcharges
or supplementary consents may be in place for discharges of certain textile
effluents. A specific UK example of discharge consents based on colour, and
specifically UV absorption, imposed by the regulatory body (the Environment
Agency) is given in Section 5.7.
Detailed technical descriptions of the most usual operations within the textile
industry have been reported by many authors (Cooper, 1978; Nolan, 1972;
OECD, 1981), along with effluent water quality data, which generally relates
directly to the water at the end of the batch operation which is then discharged.
However, many conventional wastewater quality determinants such as COD,
TOC, TDS and TSS generally go unreported. Values for other parameters, taken
from Cooper (1978), are reported in Table 3.21 along with some water
consumption valucs. The values are subject to considerable variation arising