Studies On The Treatment Of Coal And Brewery Wastewater Using Adsorption And Coagulation– Flocculation Techniques

2.5.6 PRODUCT & USES
a). Nutrition: Velvet bears can be used as a human foodstuff but require considerable care in their preparation, because of the toxic principle they contain. In many parts of Africa and Asia they are regarded as a famine food. The toxic principle can be removed by boiling and soaking the seeds in several changes of water. In parts of Asia, the seeds are sometimes roasted before being eaten and in other parts, the immature pods and leaves are occasionally boiled and eaten as a vegetable ( Bachmann, 2000).

b).Medicine: The possibility of utilizing velvet beans as a commercial source of L-dopa (which is relatively expensive to produce synthetically), used in the treatment of parkinson’s disease (PD), has received attention in recent years (Bachmann, 2000). Yields of around 4.8% are reported to be attainable from the decorticated seed meal (Bachmann, 2000). The antisnake properties of an extract of Mucuna pruriens’ seeds (MP101UJ) in vivo were recently demonstrated and one is now investigating its biochemical mechanism (Aguiyi et al, 2001). Echis carinatus venson (EV) contains a mixture of proteins that affect the COAGULATIVE cascade, causing severe Bleeding. An increase in procoagulant activity was found after a study on Mucuna pruriens (MPIOIUJ) in prothrombin activation (Aguiyi et al, 2001). Details of Mucuna’s traditional medicinal uses, chemical constituents, pharmacological activities and clinical trials have been reported in “Medicinal plants of the world” by Ross I.A, 1999.

c). Secondary: The possibility of utilizing the seed as a source of industrial starch has been investigated in Brazil and results indicate that a starch with a high viscosity, similar to that obtained from cowpeas, and suitable as a thickening agent for food products, or as an adhesive in the paper and textile industries, could be obtained (Bachmann, 2000).

2.5 .7 CHARACTERISTICS
The approximate composition of the green forage of velvet beans, on a dry weight basis, has been given as: protein 15.1%; fat 2.1; N-free extract 48.6; fibre 19.3 and ash 14.9. Digestible protein 10.7%; digestible carbohydrate 49.6; total digestible nutrients 63.4; nutritive ratio 4:9(Bachmann, 2000). The composition of the whole, dry pods has been reported as” moisture 10.0; protein 18.1; fat 4.4; N-free extract, fibre 13.0 and ash (4.2 Bachmann, 2000). The approximate composition of the mature seed is: moisture 10.0%; protein 23.4, fat 5.7;
N-free extract 51.5; fibre 6.4; ash 3.0; Calcium 0.18; phosphorous 0.99; potassium 1.36; vitamin A 50iu/100g; thiamine O.50mg/100g; riboflavin 0.20mg/100g; niacin 1.7mg/100g. The amino acids present (mg/gN) are: iso- Leucine 300; leucine 475; lysine 388; methionine 75; crystine 56; phenylalanine 300; tyrosine 319; threonine 250; valine 344; arginine 494; histidine 131; alanine 219; aspartic acid 794; glutamic acid 763; glycine 288; proline 369; serine 306 (Bachmann; 2000).

The oil present in the seeds has been found to be highly unsaturated with 47.2% linoleic acid; 14.2 oleic acid; 3.8 linolenic acid and 0.5 palmitoleic acid. The saturated fatty acids are: palmitic 19.5%; stearic 12.6; arachidic 2.2 (Bachmann, 2000). In feeding trials with rats, it was shown that the toxic principle occurs in the protein fraction of the seeds and not in the oil (Bachmann, 2000). The toxic principle L- dopa, 3-(3,4-dihydoxy phenyl)- Lalanine is present mainly in the amounts equivalent to 1.5% of the whole seed weight . It has been suggested that the presence of free L-dopa is the reason that velvet beans are relatively immune to attack from insects and small mammals. (Rehr,1973). In addition to L-dopa, a new amino acid (- )- methyl-tetra hydroisoquinoline has been isolated recently from velvet beans (Bachmann, 2000).

2.6 COAGULATION/ FLOCCULATION
Coagulation is the destabilization of colloidal suspensions by neutralizing the electric forces that keep the suspended particles separated (Browstow et al, 2009).The aggregates formed in the coagulation process are small and loosely bound, their sedimentation velocities are relatively low- although higher than in gravity separation.Given the nature of the process, the results are strongly dependent on pH and its variations (Brostow et al, 2009).

Flocculation is caused by the addition of minute quantities of chemicals known as flocculants. (Browstow et al, 2009). Flocculation is the agglomeration of destabilized particles into microflocs and then into bulky floccules which can be called floc (Menkiti, 2007). Flocculation is the transport step that causes the necessary collisions between the destabilized particles and subsequent floc aggregations or floc break up (Jin, 2005).

2.6.1 COAGULATION / FLOCCULATION PROCESS
In water and wastewater treatment practice, the term coagulation and flocculation are not synonymous. Coagulation is used to describe the initial process (involving rapid mixing) whereby the original colloid dispersion is destabilized, principally by charge neutralization. Flocculation describes the subsequent process whereby the destabilized colloids in the micro size range undergo aggregation and particle growth into millimeter sized flocs. Since the coagulation stage, and the early phase of the flocculation occur very rapidly their distinction in a practical treatment sense has very little meaning (Leprince et al, 1984). Morover, flocculation is much more effective than coagulation since the so called flocs are larger and more strongly bound than the aggregates obtained by coagulation (Brostow et al, 2009).

2.7.2 CLASSES OF COAGULANTS .

Coagulants can be classified into two groups namely:

(a) Organic coagulants
and
(b) inorganic coagulants (Aqua Ben, Co, 2001).

a). Inorganic of Coagulants:
The use of inorganic metal salts as coagulants is well established. The three main inorganic coagulants include the following:
a). Aluminum derivatives
b). Iron derivatives
c). Lime

b). Organic coagulants (poly electrolytes):
These are water-soluble organic polymers that are used as both primary coagulants and coagulant aids. Polyelectrolytes are organic macromolecules. Polyelectrolytes may be made up of one or more basic monomers (usually two), (Baarlsurd et al, 1994).

Polyelectrolyte are classified as non-ionic, Anionic or cationic depending on the residual charges on the polymer in solution.
i). Non- ionic polyelectrolytes:
These are polymers with a very low charge density: non- ionics are used to flocculate solids through bridging. A typical non-ionic is a Polyacrylamide
(WST, 2005).
ii). Anionic Polyelectrolytes:
These are negatively charged polymers and anionics are normally used for bridging to flocculate solids. These are manufactured with various charge densities, though the intermediate charge densities are usually the most useful. Typical example is the acrylamide based anionics (Menkiti, 2007).
iii).Cationic Polyelectrolytes:
These are positively charged polymers and come in a wide range of families, charge densities and molecular weights. Cationics can be thought of as double acting because they act in two ways: charge neutralization and bridging. Examples include the following: natural organic polymers (Alignates); artificial organic polymers (amide derivatives, cellulose derivatives); synthetic organic polymer (quarternary salt of polyvinyl pyridine) (WST, 2005).

2.6.3 CLASSES OF FLOCCULANTS
Flocculants can be classified into
a). Inorganic and (b) Organic flocculants and both are in use (Brostow et al, 2009).
a). Inorganic flocculants:
Inorganic flocculants are used in very large quantity, they leave large amounts of sludge and are strongly affected by pH changes. (Brostow et al,2009). They include salts of multivalent metals like aluminum and iron and are applied most often- at high concentrations (Brostow et al, 2009).
b). Organic flocculants:
Organic flocculants are typically polymeric in nature, by contrast to inorganic ones, they are effective already in ppm concentrations (Brostow et al,2009). These polymeric flocculants are classified into synthetic and natural water-soluble polymer (Brostow et al, 2009).

i).Natural polymers:
These includes
1). Polyscaccharides, mainly starch and its constituents
2). Different types of guns
3). alginic acid
4). Cellulose and its derivatives
5). dextran
6). glycogen e.t.c.
ii).Synthetic Polymers