Sludge is produced as a beltway merchandise of a H2O intervention procedure. The sludge is normally disposed on land, but this consequence as a wellness jeopardies and inauspicious effects on the ecosystem. All metals above certain concentration have side effects to human being. Among the most risky heavy metals are Cardium, Lead, Mercury and hexavalent Chromiun, the first three being toxic at all concentration and have non a known biological map ( Moeletsi et al, 2004 ). When consumed by human, these heavy metals can do encephalon and bone harm and every bit good as kidney and liver upset ( Moeletsi et al, 2004 ). Although there are metals that are indispensable to workss and animate beings under low concentration ingestions ( As, Cr, Cu, Co, Fe, I, Ni, Zn, V, Mn and F ) ( Moeletsi et al, 2004 ).
Sludge disposal issues
The heavy metals concentration largely depends on the industrial waste affair part to the waste H2O system. The effluent from domestic beginnings has normally low concentration of some of the heavy metals ( Richard et al, 2004 ). High concentration of heavy metals in sludge is of high concern where the sludge is being applied in an agricultural harvest, therefore being consumed by human organic structure. Another concern is if the dirt consumption and accumulates this heavy metals to a phototoxic degree and their incursion to land H2O ( Halday, 2007 ). A concern is besides adhering to the environmental statute law and restriction of heavy metals concentration in sludge when disposed in land and harvests
In this survey the sludge from two beginnings, industrial and residential will be analysed to see what is in the sludge and how much of it is in the sludge. Particularly the analysis is for heavy metal such as Manganese, Zinc, Iron, Copper, Lead, Nickle, Chromium, Cadmium, and Mercury. The analysis will be carried through with analytical techniques such as AA and SEM-EDAX.
Atomic soaking up spectrophotometer ( AA ) analysis for metal content and SEM-EDAX images analyse mineral composing, form and size of the mineral.
Current intervention of the sludge
Sludge is formed from waste H2O mending procedure where solids are being separated from liquids. The content of solids in the intervention works varies for different workss and how the works is operated. Effective intervention of sludge needs a important cognition of the features of sludge being processed. The sludge from domestic end products is from the Cape flats wastewater intervention works and sludge from industrial end product is form Athlone effluent intervention works. Not much item is given about the physical process that is followed to further handle the sludge at the workss as this information is non disclosed ( company belongings ). However the anaerobic digested sludge can non be utilized for farming intent, for the ground that it contains high concentration of Cr.
Current use of the sludge
The sea is the concluding receiving system of all wastewaters with the close shore Waterss of False Bay acquiring approximately 57 % and Table Bay acquiring 29 % of the municipal waste affair discharges. A batch of these localised pollution are nearby to look up to entertaining topographic points of which H2O quality is a most of import concern to the wellness of the people. Industrial influent recycles about 60 % of its influents, and it cotains a fear sum of metals in it ( Gasson, 2002 ).
Approximately 27 % of moisture sludge is reused in municipality utilizations and composting. The usage of land make fulling being the favored dumping system without uncertainty puts more involvement on the province of the environment. Number of muffling sites ( about six ) exists in the Cape flats country, and this leads to high chance of land H2O taint. As a lower limit the Swartklip moistness site is closed because of leach Ate toxic waste to groundwater. A great trade of the sewerage sludge it is non discharged in an environ-mentally accountable manner, where this increases the concern with respect to the quality of land H2O ( Gasson, 2002 ).
Table 1, waste beginning end product ( tons/yr ), and entire recycling, 1998 from Gasson, 2002
|Tons/yr by income group||Tons/yr recycled or reused||Recycling as % of entire recycled|
|Residential||895 900 44 %||Informal 0,35||102 386||41 000 compost||8 %|
|Low-mid 0,7||300 547|
|High inc. 1,3||492 967|
|Industrial||499 900 24 %||0,46||
186 700 metals
93 600 paper
13 000 glass
|Damp sludge||245 200 12 %||65 000||14 %|
|Sum||2 050 800||485 000 2||100 %|
There has been a concern in the passed old ages with respect to increase in heavy metal content in sewerage. Particularly Cape Town is confronting really rigorous Torahs against waste handling and disposal.Research significance
Word picture of the happening and mineralization of heavy metals in sewerage sludge is an of import process before the sludge can be exposed and applied in agribusiness as a fertiliser, since there is a hazard of accretion of toxic elements by the dirt or the workss. However the accretion of high concentration of heavy metals in the sludge could ensue in new environmental consideration ( Angiliclis and Gibs, 1991 ; Obrator et Al, 1997 ).
- When recycled sludge ash could be used as alternate edifice stuff ( in cement production )
- When extracted from the sludge the heavy metals can be used for different intents.
The consequence of the probe will be used to can do suited remarks about disposal hazards and alternate use methods.
It has been estimated that each individual contributes about 60g of solid waste everyday.
In add-on, metropoliss consume about 75 per centum of the resources on Earth and bring forth about 75 of the wastes on the Earth, and the magnitude will increase with old ages motivated by population addition and privileged fortunes ( Gasson, 2002 ). As a consequence it is of paramount importance to cover with waste affairs and the waste managing methods.
South African context
Cape Town has about three million citizens which is instead still a little metropolitan country in comparing with other metropoliss such as Lagos or Cairo, which have citizens in the part of 13 million, which are known to be among the biggest metropoliss in the universe. In the Cape metropolitan country the connotation is to increase residential waste recycling by 15 % ( Wright-Pierce, 1999 ).But solid waste is expected to increase by 1,8 % yearly for following decennary ( Gasson, 2002 ). This is of grounds that effluent intervention workss are on demand, and the waste direction has to able to can manage the big expected capacity.
Wastewater works in Metropolitan Area in Cape Town
In Cape Town domestic waste and industrial waste wastewaters are treated at 23 waste H2O intervention works where about 191 million ( dozenss ) of the treated wastewaters are discharged every twelvemonth ( Cape Wastewater Consultants, 1999b ).
The Table2 below shows the capacity of H2O intervention workss in the Cape Town metropolitan. The Cape flats H2O intervention works is therefore revealed to be holding the highest capacity for handling 200 milliliter of effluent per twenty-four hours. Hence this survey investigates the heavy metals concentration of the sewerage sludge from the two biggest workss in Cape Town, Cape flats and Athlone, in the Western Cape, with a position of measuring their viability to be used as Agricultural fertilisers in footings of their metal contents.
Table 2. Bulk effluent intervention works within Cape Town Metropolitan Area
|Name OF WASTEWATER TREATMENT||Capacity|
|Athlone Wastewater Treatment Works||120,0 M/day|
|Potsdam Wastewater Treatment Works||32,0 M/day|
|Wesfleur Treatment Works||14,0 M/day|
|Melkbosstrand Wastewater Treatment Works||2,5 M/day|
|Llandudno Wastewater Treatment Works||0,5 M/day|
|Dover Wastewater Treatment Works||0,1 M/day|
|Oudekraal Wastewater Treatment Works||0,03 M/day|
|Cape Flats Wastewater Treatment Works||200,0 M/day|
|Zandvliet Wastewater Treatment Plant||55,0 M/day|
|Mitchell ‘s Plain Wastewater Treatment Works||37,5 M/day|
|Macassar Wastewater Treatment Plant||34,0 M/day|
|Wildevoelvlei Wastewater Treatment Works||14,0 M/day|
|Simon ‘s Town Wastewater Treatment Works||5,0 M/day|
|Miller ‘s Point Wastewater Treatment Works||0,03 M/day|
|Bellville Wastewater Treatment Plant||46,0 M/day|
|Borcherd ‘s Quarry Wastewater Treatment Works||30,0 M/day|
|Kraaifontein Wastewater Treatment Plant||7,0 M/day|
|Scottsdene Wastewater Treatment Plant||4,5 M/day|
|Gordon ‘s By Wastewater Treatment Plant||3,5 M/day|
|Parow Wastewater Treatment Plant||1,2 M/day|
Beginning: ( Gasson, 2002 )
The Cape flats country is a large residential country in Cape Town, therefore produce a big measure of waste. This works is the lone works that produces dry sludge, and dry sludge occupies a smaller volume compared to liquid sludge. Furthermore dry sludge can be incinerated and land filled depending on the concentration of heavy metals content, instead the ash is used in the cement fabrication industry blink of an eye of wash uping merely one disposal method ( Agricultural fertiliser ). Athlone is a partially residential and partially industrial country with a batch wastewater coming from the industry. Figure1 below show a map of the Cape metropolitan country and demo the where the two workss of concern are situated.
It has been adequately discovered by numerical research workers viz. Halday, 2007, Moletsi et Al, 2004 and Gasson, 2002 that preponderantly residential workss contains low degree concentration of heavy metals, where else the preponderantly industrial country workss shows to hold a high concentration of heavy metals. But their find still remains uncomplete without a elaborate cognition of the beginning of heavy metals in the domestic beginnings of the works.
For many old ages land has been used as a receptor of waste H2O, the normally used being application on land for agricultural intent. As the population in South Africa increase the land became more hard to reserve for this intent, and besides the wellness became more of a concern. Furthermore the universe involvement on environmental issues in on an addition.
“ The Polokwane declaration” In 2001September South Africa committed itself to accomplishing 50 % decrease in the volume of waste generated and 25 % decrease in volumes of land-filled waste by 2012 and a zero waste program by 2022 [ 12 ]. With this, one may state is to a certain extent excessively ambitious sing the increasing population growing.
South Africa is presently explicating its National Waste Bill. With this enterprise we are anticipating it to implement generators to pull off their waste harmonizing to the hierarchy of waste direction in a sustainable manner. That is, industry will hold to avoid, minimise, recycle, dainty and dispose of their waste as a last resort. Action plans for the execution of statute law at a local degree is presently being discussed. The move is to guarantee that generators implement minimisation programmes ( NEMA 107 of 1998 ).
Occasionally taint of the coastal lakes has happened in the Cape Flats and at Noordhoek where high possibility of unwanted result for the wellness of the populace and the environmental ( Gasson, 2002 ). Cape flats and Athlone H2O intervention workss are within the attention zone and hold a first bill of exchange plus direction program that province in conformity imposts of seting in action ways of pull offing the plus ethically ( Cape Town H2O substructure, 2004 ).
In 2003 Richard et Al, had done a similar probe on a all the Cape metro waste intervention workss, and the consequences showed that Cape flats and Athlone contains high concentration of heavy metals but still below the current DWAF ( section of H2O personal businesss and forestry ) guidelines bounds.
Table 3 Heavy metal content of Athlone and Cape flats wastewater workss compared to current guidelines bounds, taken from Gasson 2002
|Wastewater intervention plants||Copper( µg/l )||Lead( µg/l )||Zinc( µg/l )||Aluminum( µg/l )||Mercury( µg/l )|
|Datas: Jan to Dec 2003||Natural||Iron||Natural||Iron||Natural||Iron||Natural||Iron||Natural||Iron|
|Current DWAF guidelines||1000||100||5000||Non||20|
The sludge, arising signifier effluent interventions are the remains ensuing in the primary, secondary and third interventions. A typical metals content of effluent sludge consist of the following with a average ( mg/Kg ) ; Arsenic 10, Cadmium 10, Chromium 500, Cobalt 30, Copper 800, Iron 17000, Lead 500, Manganese 260, Mercury 6, Molybdenum 4, Nickle 80, Selenium 5, Tin 14 and Zinc 1700.
At present the most normally used sludge managing option in Europe is agricultural ingestion, other new utilizations and the waste shit topographic points. The options used reflect the political, national, historical, geographic, legal and economical circumstance of that country. Anterior 1998 municipal sludge ‘s where chiefly dumped at the sea and used on agricultural harvests ( Odegaard et al, 2002 ). After 1998, Europe statute law forbidden the damping of sewerage influent in the sea, so as to salvage the marine environment from toxic elements. One may state that universe broad the chief disposal method of sewerage sludge is agricultural usage. In EU thirty seven per centum of the sludge formed is being used up in agricultural application, 40 % land filled and 12 % is used in forestry and the others.
With regard to the values of sustainable development certain restrictions have to be forced when the sewerage discharge methods are applied.
Table 4 EU Restriction on sludge direction ( Fytili and Zabaniotou, 2006 ).
Sludge direction method Restrictions
Agricultural usage: Sludge constituents ( what is in the sludge )
: Concentration of foods and heavy metals in the sludge
: Accepted by the nutrient industry and the populace
: Technical limitations ( managing of the sludge )
Land fills: Organic affair in the sludge
: Restriction of land
: Permitted new land fills countries
: Recycling necessities
Reclamation: Licenses of constructing an incineration works
Wastewater sludge can be both economical and good application in an agricultural harvest, for this ground word picture of sewerage sludge before application on land is a critical procedure. The heavy metal content of a waste watercourse from a domestic ( residential ) country is low, and the heavy metal content of a watercourse from an industrial country is expected to be high. As a consequence sewerage sludge from a preponderantly residential country may perchance be used as composed in agricultural harvests without jeopardizing workss neither land H2O with toxins.
Aim and aims
Equally much as 27 % of sewerage sludge in the Western Cape is recycled for municipal utilizations, composting, and agribusiness ( Gasson, 2002 ). It is good known that all sewerage sludge contains changing sums of heavy metals depending on the feeding country ( Richards et al., 2004 ).
The purpose of this survey is as follows:
- The chief purpose of the survey is to find whether sludge from any effluent intervention works in the Western Cape may be used safely for composting intent, or whether it could take to build-up of heavy metals in groundwater
- An surrogate purpose is to look into simple intervention techniques with the accent of repossessing heavy metals from the sludge incorporating high sums of heavy metals.
Sewage sludge from waste H2O intervention workss handling effluent from two different feeding countries in the Western Cape will be collected for survey. One country is a preponderantly domestic country ( Cape flats ), the other a preponderantly industrial country ( Athlone ). The sewerage sludge will be characterised in footings of heavy metal content and minerals. Besides the probe of the current intervention and use of the sewerage sludge in the WC part will be discussed.
The analysis subdivision will consist the techniques such as:
- Atomic Absorption ( AA ) and
- SEM -EDAX
- Current intervention procedure of the sludge from Cape flats and from Athlone country in Western Cape ;
- Current use of the sludge ;
- Metal content of the sewerage sludge ;
- Is it possible to pull out the minerals from the sludge ;
- Make suited remarks about disposal hazards and alternate methods.
Two samples viz., natural sludge and high temperature treated sludge ( ash ) from each sludge beginnings will be analyzed by utilizing AA and SEM -EDAX
The sewerage sludge will collected from Cape flats H2O intervention works in pellet signifier. The sample will be mixed by flicking the bags received to 1/16 fraction to do certain a representative sample is obtained. A representative sample of the sludge will be put in an oven at temperatures about 500?C for 12 hours, in order to fire out the organic affair in the sludge. Sludge and sludge ash will be digested in HCl for analysis in AA ( method to be farther researched ).
Mounting Samples for SEM analysis
The undermentioned stairss are to be followed ;
- Mix the rosin
Samples are mounted for SEM analysis utilizing Epofix
The mix formula is 7 parts rosin to 1 portion hardener
This 8ml mix is adequate to mount two samples
Use a 20ml syringe for the rosin and a 5ml for the hardener.
Draw up the rosin into the syringe and shoot the rosin easy into the Grey blending cup so as non to organize bubbles. Clean the syringe instantly
Inject the hardener bead by bead onto the rosin and seek to fall in all the formed bubbles in making so. Clean the syringe instantly
Use the ice pick stick to blend the rosin mix carefully. Clean immediatly
- Pour thin bed ( hardly covering the floor of the mounting cup ) of rosin in each climb cup
- Topographic point the samples in to the climb cup
- Cover the samples wholly with rosin mix, and clean the Grey blending beaker
- Leave the sample to put for at least 15 hours
- Remove the mounted samples from the mounting cup by inverting the gum elastic cup and forcing the sample out.
Sample grinding and smoothing for SEM
The undermentioned stairss are to be followed ;
- Cut the sample
- Clean the sample
- Coarse grind the sample to take the bed of rosin that covers the sample surface and to crunch level the semilunar cartilage ends on the dorsum of the sample so that it will lie level in the SEM.
- Final swot and smooth the sample so as to take the Markss as they may debar the negatron beam and influence the result of SEM analysis
It must be noted that the experimental processs are subjected to alterations such as improved methods that are recognized through extra literature reappraisals and will be updated as this alterations are being made.
- SEM-EDAX, installation at the Geology section.
- AA at the procedure technology section.
Undertaking program and resource demands
- A’varez, E.A., Mochon, M.C., Sachez, J.C., Rodriquez, M.T., 2002. Heavy metals extractible signifier in sludge from waste H2O intervention works. Chemospher. pp 765-775
- Angeliclis, M., Gibbs, R.J., 1991. Heavy metals in urban sewerage sludges chemical signifiers and possible handiness. Treat. Use sewerage sludge Liq.Agric. wastes. Pp400-404.
- Carter C. A., 1994a. Department of Water Affairs and Forestry ( DWAF )Drumhead Report. Western Cape Systems Analysis. DWAF Report No P G000/00/5293
- Carter C. A., de Smidt K., 1994. Department of Water Affairs and Forestry ( DWAF ) (Main Report.Prepared by Inc. in association with BKS Inc. as portion of the Western Cape System Analysis. DWAF Report No PG000/00/5193.
- Small P. R., 1998. Department of Water Affairs and Forestry,Feasibility Study of the Skuifraam Dam Supplement Scheme, Main Report.
- Fytili, D., Zabaniotou, A., 2006, Utilization of sewerage sludge in EU application of old and new methods-A reappraisal.Department of chemical technology, Aristol Universty of Thessalonika., Greece.
- Gasson, B., 2000. The Urban Metabolism of Cape Town, South Africa: Planing jussive moods in an ecologically unsustainable city. Czech Republic,
- Gasson, B., 2002. The ecological footmark of Cape Town: Unsustainable resources usage and planning deductions. pp 12
- Halday, I., 2007, Study of tracts of heavy metals in sewage system. pp 3, 12-15
- Herman, H., Hahn, E., Hoffman, Hllavar, O., 2002. Chemical H2O and effluent intervention seven, IWA, Gothenburg. pp 331
- Moeletsi, M., Mazema. H., Halday, I., 2004. Strategy for extenuating the impact of heavy metals in effluent and the economic and environmental deduction for the metropolis of Cape Town. pp570-575
- Odegaard, H., Paulsrud, B., Karlsson, I., 2002. Wastewater sludge as resource: sludge disposal schemes and matching intervention engineering aimed at sustainable handling of effluent sludge. Water Sci Technol. Pp 295-303
- Richards, H., Moollan, R.W., Beceri, R., Moche, D., Rus, H., 2004, An overview of the heavy metals concentrations found in municipal effluents and effluent sludges in the metropolis of Cape Town. pp.1515.2-1515.5.
- Wright-Pierce, P., 1999. Feasibility Study Towards and Integrated Solid Waste Management Plan for the Cape Metropolitan Area, Cape Metropolitan Council, Cape Town.
Zufiaurre, R., Oliver, A., Chamorro, P., Nerin, C., Calizo, A.,1998. Speciation of metals in sewerage sludge for agricultural utilizations. Analyst123. pp 255-259