ASSESSMENT OF INDUSTRIAL WASTEWATER POLLUTION IN DEVELOPING COUNTRIES – CURRENT POLLUTION LEVEL IN RWANDA

Sosthene Mubera*, Philip Ochieng Ogada and Dragan Cigoja. UNEP-Tongji Institute of Environment for sustainable development. College of Environmental Science and Engineering. 20092, China. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

In both developed and developing countries, wastewater treatment has been a serious matter on small and large scale.Created industries, enterprises and factories manufacturingfinal products from raw materials use fresh water in their processeswhich result in wastewater heavily loaded with various pollutants.Pollution level depends on the type of factory or industry.Although some industries /factories date from nineties (90s), Industrial sector is quite new in Rwanda.Industrial reforms started early 2000 with Rwanda vision 2020 launch where by 2020, industrial and service sector will contribute about 42 % of country's GDP.BOD, COD, Nitrates and phosphates were measured, Analyzed and show that Horizon Sopirwa, AMEKI color, UTEXRWA and Nyanza dairy have the highest concentration in Nitrate, Phosphate, BOD and COD respectively.Results found that at least each factory/industry has surpassed Rwanda Bureau of Standards' effluent limits given on the appendix.Pretreatment and further analyses have been recommended in order to deepen Rwanda's water pollution understandings and taking environmental pollution prevention measures.
In developed countries, integrated water management presents accessibility of domestic, urban and industries facilities connected to water supply pipes and sewer pipes flowing wastewater in treatment plants where wastewater passes through number of treatment stages before effluent in the environment.Industrial wastewater treatment bloomed since 1990s when countries realized an increase of pollution percentage in cities and more investment being made in industrial sector.Modern countries have developed wastewater management practice to minimize 717 On the other hand in developing countries; industries are increasing countries' GDP and creation of new jobs but no appropriate sanitation goes with this economic growth.Implementation of standards must go in parallel with development in environmental agencies for monitoring, controlling, regulating to enhance good water quality and non-fresh water stress which is being observed and leading to waterborne illnesses.In addition; industries may not want to treat their discharges because of high operational costs and big amount of energyuse to treat wastewater resulted fromdifferent types of processing of industries [3].[6].The agriculture and manufacturing sectors are the most present sectors in many African countries.Focus is put in agriculture, manufacturing, transport and development of infrastructures which consume and discharge much water during processing.Most of the water divert for human use as in irrigation and an increasing demand due to agricultural and industrial production undelay water stress in many African regions.During years of African industrial development; problems with sanitation have arisen, factories and industries discharge illegally polluted wastewater in the fresh water bodies and therefore cause diseases [7].
Like everywhere, industrial sector became a great but challenging opportunity for Rwanda and its environment.Industriesextract fresh water upstream in surrounding water bodies and discharge water at downstream of the same water body.Water is the single largest factor in goods production for Rwanda.It is used in different sectors including agriculture, water supply, home facility, commerce, and industries.After production processes, water is discharged as wastewater where it reaches the environment containing a given amount of nutrients, chemicals, heavy metals, and organic matters which are usually higher than Rwanda bureau of standards (RBS) effluent limits [8] The aim of the present paper work is to analyze the pollution level of organic matter in effluent wastewater from considerable factories and facilities in Rwanda.

Materials and Methods:-
Nitrate Determination:-Nitrate concentration in wastewater can be determined based on the diazotization of sulfanilic acid by the available nitrite and subsequent coupling with an agent such as α-Naphtylamine (α=1,2,3).Using N-(1-naphthyl)ethylenediaminedihydrocloride presents an advantage of color development time reduction to 2 minutes while the coupling of diazotized sulfanilic acid with α-naphtylamine takes from 10 to 30 minutes for full color development and with α-naphtylamine acetate ;the color development takes 30 minutes( [9].During the test, a filtered sample is passed through a column containing granulated copper-cadmium in order to reduce nitrate to nitrite.At this stage, the nitrite is determined by diazotizing with sulfanilamide and coupling with N-(1-naphthyl)-ethylenediamine hydrochloride to form a highly colored azo dye which is determined colorimetrically.The intensity of coloration is referred to the concentration of the available nitrites ion present in samples.The range of dosage is 0.05-10mg/L nitrate-nitrite nitrogen [10], Phosphorus determination: Ammonium molybdate and potassium antimonyl tartrate react in acid medium with orthophosphate to form a heteropolyacid that is reduced to intensely colored molybdenum blue by ascorbic acid [11].
There is a direct relationship between the intensity of the color of a solution and the concentration of the colored component which it contains.In some cases it is easy to determine the concentration of a sample based on its color intensity by comparing its color with those of a series of solutions of known concentration of the analyte species.In other cases, by UV spectrophotometer, the amount of electromagnetic radiation in the visible region of the spectrum absorbed by a colored solution is often directly proportional to the concentration of the colored species as defined by the Beer-Lambert Law (A = εcl).During test ; a beam of light of intensity Io is focused on a sample, and a portion, I, is absorbed by the analyte species.
To mathematically express the spectrometer measurement, we use Beer-Lambert Law [12]; Thus, the absorbance of a solution is directly proportional to its concentration ( c), as long as the solution path length (l).Phosphate reacts with ammonium molybdate in the presence of suitable reducing agents to form a blue colored complex, the intensity of which is directly proportional to the concentration of phosphate in the solution.The phosphate content of the wastewater sample is obtained by first plotting the absorbance of a series of standard solutions against the corresponding concentrations, thus giving a calibration curve.The concentration of phosphate in the unknown sample is thenbe determined from the graph [13].

Biochemical Oxygen Demand (BOD):
Biochemical Oxygen Demand for 5 days (BOD 5 ) is a chemical procedure for determining the amount of dissolved oxygen required by biological organisms to degrade organic matter present in a body of water under a certain temperature over 5 days [14].After sampling wastewater, different steps in BOD 5 test were done in laboratory and the BOD 5 of wastewater was calculated using equation [15].
Where: D1= dissolved oxygen of diluted sample immediately after dilution (mg/L) D2=dissolved oxygen of diluted sample after 5-day incubation at 20 0 C (mg/L) P=fraction of wastewater sample volume to total combined volume.

Chemical Oxygen Demand (COD):
Like BOD, COD is most important water quality parameter where analysis measures the reduction of the strong oxidant potassium dichromate (KCr2O7) under highly acidic conditions at high temperature, and then correlates this reaction to standards with known levels of oxygen demand.After the digestion, the orange color persists because of K 2 Cr 2 O 7 is not reduced and its determination by colorimetric method permits to evaluate the quantity of K 2 Cr 2 O 7 consumed by oxidable matters of sample and this is expressed in terms of equivalent oxygen.Wastewater samples are diluted and added to both the standard and miniaturized COD ampules.COD samples arethen incubated at 1500C for 2 h in a dry incubator.The color intensification (green color) is proportional to the organic matter which is also proportional to the COD measured by spectrophotometer at the wavelength of 600nm.dataare plotted using Microsoft excel [16].

Calibration curves:-
A calibration is the process of establishing a relationship between two properties.In the case of colorimetric measurement, a calibration curve establishes a relationship between a sample's concentration and the amount of light it absorbs, which is a measurement of color intensity.Concentration is plotted versus absorbance and this linear relationship in a colorimetric measurement is known as Beer's Law which state that [17] 719 A=abC (6) (A: measured absorbance, a:molar extinction coefficient (constant) ,b:path length of sample cell C:Concentration ) A linear calibration has the mathematical relationship: y = mx + b, where y is the concentration, m is the slope of the line, x is the measured absorbance, and b is the intercept.But chemistry is very complex and sometimes it depends on the relationship between absorbance and concentration and may be nonlinear [18].

Figure 3:-Absorbance and concentration calibration curve
Plotting nutrients concentration in nutrient solution curve form of simple spectrophotometric techniques is presented in curves.Most likely nitrate and phosphate are suitable and most used for these techniques.Together with example of standard calibration curves obtained in laboratory, actual nutrient concentration are plotted, compared with standards curves and values determined.One of advantages is that these protocols enable the routine and sensitive measurements of nutrient solution composition requiring only a spectrophotometer and minimal use of other basic laboratory equipment [19].

Results and Discussion:-
Nitrate and Phosphate:-The maximum tolerance limit of nitrate concentrations from industrial wastewater to be discharged in the environment is 20mg/L.Resultsshow that the concentration levels of nitrates for Nyanza dairy plant and Horizon Sopirwaare relatively higher than the tolerance limit of industrial waste water discharged.Phosphate which is not toxic and have no restriction on human health or bring other organisms directly, but it has indirectly serious threat to water qualityand is considered harmful because of its impact in rapid growth of aquatic plants such as algae.Highest phosphate concentration than RBS tolerance limits is observed in BMC SKOL, Masaka Dairy, Ameki color, Nyanza dairy plant and Kinazi cassava plant.721 The pollution level of sampled zones shows that pollution will considerably increase if nothing is done to pretreat water before entering neighborhood water bodies.Results of samples from considered factories/industries shows that 30% have surpassed nitrate effluentlimits, 50% surpassed phosphates effluent limits, 80% surpassed COD effluent limits and 100% surpassed BOD effluent limits.This may cause severe water quality problems.Phosphate and nitrates will promote excessive growth of algae and other aquatic plants, as the algae and other aquatic plants die and decompose high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.High COD and BOD levels decrease the amount of dissolved oxygen available for aquatic organisms.Low dissolved oxygen reduces cell functioning, disrupts circulatory fluid balance in aquatic spices.This result in individual organisms' death, releasing diseases to the community and creating unsafe water supply sources.
[5]gest economies (Nigeria & South Africa)[5]on the continent.Industrial development implies opportunities for employment growth, country's population wellbeing grows and urbanization takes place in all sectors 4 3− + 12 M 0 O 4 2+ + 24H + H 3 PO 4 (M o O 3 ) 12 + 12H 2 O( Phosphomolybdic acid) (1) Industrial sector plays a major role in pollution of the environment.Highest concentration depends on the type of the raw material.Among Rwandan industries'wastewater discharge; highest values are observed at Horizon Sopirwawith high Nitrate concentration (32.2 mg/L) , AMEKI color with highest phosphate concentration (36mg/L), UTEXRWA with highest BOD concentration (183.75mg/L) and Nyanza dairy with highest COD concentration(1550mg/L).Further studies on metal, PH, turbidity are recommended for investigation of all improper wastewaterdischarge which continuously pollutes water, environment and disturbs the balance of ecosystem by killing various animals, plants and human in the surrounding environment.Pretreatment before effluent is highly recommended to reduce the amount of nutrients, chemicals, metals and other types of pollutants entering in the environment.