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Abstract:
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It is the aim of the government of the Republic of Kenya that by the year 2000 or earlier if possible, the entire population will have access to a safe water supply at close proximity. However, investigations carried out in 1983 show that only 23 % of the total population has piped water supply and the vast majority in the rural areas obtain water directly from rivers. It is therefore apparent that there will be serious healthrisks if waste waters from expanding industries and increasing urbanisation are not treated and control enforced during the interim period. In this report a review has been made of the existing industrial discharge control systems both international and local. It was found that the foundation of a good control system must be a specification of the quality of waters on which legitimate uses depend. Thus it is necessary that ambient water quality standards for all streams be established. Discharge standards for most of the industries in Kenya have already been set. But a survey of industrial effluent quality of all three tanneries studied showed that none of them meets the allowed limits. In Bulleys Tanneries', for example, the allowed discharge quality is 20 mg O2/l BOD5 amd 30 mg/l suspended solids. The lowest values out of five grab samples analysed were 460 mg 02/l BOD5 and 117 mg/l suspended solids. Chromium concentration should not exceed 0,05 mg/l but the observed chromium ranges from 1,25 - 35 mg/l. It must be noted however that these standards mostly originate from foreign sources. The "20/30" rule has its origin in a report of river pollutionin England and Wales by a Royal Commission on Sewage disposal that was set up as far back as 1898. Effluent quide lines which are proper for Kenyan conditions, taking into account hydrological, climatic, sociological and economic situation of the country, should be developed. Industry should pay for damaging the environment. The less it damages the less it has to pay. The same is true if the damage is great the more unprofitable it is for the industry. All these economic incentive methods are not being used in Kenya. For example, even after recommending the use of Mogden's formula as the basis of charging industrial effluent. When it is discharged into municipal sewerage system, way back in 1972, Fur and Wools Tannery still pay their sewerage charges according to the hydraulic loading, regardless of whether the effluent is stronger than domestic sewage. However, industry should be forced to build waste water treatment facilities which they are going to operate and maintain. But the goverment should also realize that industry does not make direct profits from waste water treatment facilities and hence it should provide more attractive measures to industry by waiving and reducing taxation on equipment, machinery and chemical which are going to be used solely for the purpose of environmental protection. In-plant measures for reducing discharges and wastes from tanneries have been discussed. A survey in all three tanneries studied showed that these measures have very rarely been applied. In Double Diamond tannery recirculation of chromium liquors has been practiced and an attempt is being made to recoverchromium from the sludge. Water and chemical cönsumption in the industries is still quite high though technologies exist for reducing the inputs and still maintaining the required product quality. Technologies exist for treating tannery waste waters to the required design quality. In all the three cases studied, none of the effluents had a quality any where near the design conditions. For example Bulleys Tanneries effluent treatment plant was designed to achieve an effluent quality of "20/30" standard. The lowest values obtained from five grab samples analysed were 460 mg O2/l BOD5 and 117 mg/l suspended solids. In Fur and Wools tannery only trace of chromium is allowed in the discharge. The observed chromium concentration ranges from 1,3 to 39 mg/l. Facilities exist for raising pH with lime to optimize chromiumhydroxide precipitation but are rarely if ever used. Douple Diamond tannery has been disposing its waste waters on land by spray irrigation. The sodium absorption ratio of this waste water ranges from 30 - 70. The electrical conductivity ranges from 4000 muS/cm - 10000 muS/cm. This shows that water is not suitable for irrigation of crops. From the soil analysis conductivity was quite high and calcium was also quite high (259 g/kg calcium). A thorough study on the effect of waste waters on soil should be made. However, from a water pollution point of view irrigation could still be a means of waste water disposal if it has no effect on water sources. The responsibility of monitoring should be chared by both Water Pollution Control Authority and industry. The industry should bear in mind the benefits it can get from a comprehensive monitoring programme. Lastly, the legal system at the moment needs a lot of adjustment. Up to now it fails to define what is pollution and hence the enforcing officers can not be able to do their work as effectively as they would wish. /Kir09 |