Keywords: Reduction, nitrate, phosphorus, RO-reject wastewater, laboratory scale, pilot scale, effluent quality

Transcription

1 Treatment of Concentrated Nutrients in reject Wastewater of Reverse Osmosis Process treating Tertiary Effluent from Conventional Biological Treatment of Municipal Wastewater Abulbasher Shahalam, Kuwait Institute for Scientific Research, Kuwait Hader Al-Rashidi, Ministry of Public Works, Kuwait Abdullah Abusam, Kuwait Institute for Scientific Research, Kuwait Abstract: Wastewater reclamation and its reuse for beneficial purposes is a common goal in all countries particularly in water stressed countries around the world. Cutting edge technologies such as reverse osmosis (RO), micro and ultra filtration etc. are often used to purify wastewater effluent generated in conventional systems. However, the rejected wastewater from these processes is usually laden with concentrated nutrients, salts, inorganic materials while it is devoir of organic materials those are removed in the course of treatment. Safe disposal/reuse of these wastewaters is a growing concern. A study was carried out to investigate a number of selected processes that have potential of removing the nutrient concentrates from the reject wastewater. At bench-scale, three most promising processes were developed unifying available unit processes proven to reduce nitrogen and phosphorus in brackish water and they were tested with synthetic RO reject water. The processes were: A. Up-flow sludge blanket filtration process; B. Cascaded aerator system with partial anaerobic condition and C. Denitrifing process with bacterial growth on fixed anaerobic porous media followed by algae pond. Three carbon sources methanol, acetate and glucose were supplied in proportion of chemical composition of biological cell at microbial level. Various concentrations of this carbon sources were tried separately in 79 test cases. Process C appeared to be the best in removing total nitrogen and phosphate at ranges of 81-85% and 87-92% respectively. The process C was tested at pilot scale using actual RO reject wastewater at 1 m 3 /d transported from an advanced wastewater treatment plant in Kuwait. Three months continuous operation generated 55 sets of daily data. The results indicated that in average total nitrogen and total phosphorus concentrations of 76 mg/l and 29 mg/l in RO reject wastewater can be removed by average of 76% and 86% respectively. Average concentration of total nitrogen and total phosphorus in the final effluent remained at 13.9 mg/l and 3.3 mg/l respectively. The unit cost of implementing the process C is expected to be 0.03 KD/m 3 (1KD 3.5 USD) without the use of external carbon source. In such case, instead of external carbon source, primary treated wastewater can be mixed with RO reject water and this modification can approximately add about 10 mg/l of BOD 5 equivalent in reject water to be treated in the tested process. Keywords: Reduction, nitrate, phosphorus, RO-reject wastewater, laboratory scale, pilot scale, effluent quality

2 Introduction Desalinated seawater is the main supply of water in middle-eastern countries. In order to augment the water supply from non-conventional sources, these countries adopted a policy of reusing the treated wastewater for irrigation purposes. Towards this goal, a pioneering advanced treatment plant with a target capacity of 500,000 m 3 /d has been commissioned in Kuwait in 2004, Kuwait. The plant utilizes conventional-biological processes for treating wastewater up to tertiary level. The tertiary effluent is further treated through advanced processes of ultra filtration (UF) and reverse osmosis (RO). The ultimate goal is to recover nearly 85% of treated effluent for reuse. Most of the remaining portion of wastewater is the reject of RO systems. Salts are concentrated in the reject water along with nitrogen and phosphorus. Average nitrate concentration and average nitrite concentration in the effluent of traditional biological-treatment plant treating wastewater up to tertiary level in Kuwait range from 3.4 to 0.2 mg/l and from 0.15 to 0.03 mg/l, respectively (MPW, 2001a, MPW, 2001b and MPW, 2002). Phosphate level in tertiary water ranges from 26 to 12 mg/l. Actual records ( ) of the quality of effluent water of the treatment plant showed average concentrations of total nitrogen and phosphorus of 1.33 and 2.26 mg/l, respectively (KISR, 2007a). From a comparison of nitrogen and phosphorus concentrations in tertiary and final effluent, it is apparent that concentrations of these elements are obviously high in the RO reject water. The disposal or reuse of untreated RO-reject water from this wastewater-treatment plant has raised serious environmental concerns. Direct disposal of this water in a water-body may invigorate the growth of aquatic masses causing environmental problems (KEPA, 2001). Disposing on land has potential of concentrating salts and nutrient compounds in soil and contaminating groundwater. It appears that RO-reject water produced from this advanced treatment plant needs some kind of further treatment for removing concentrated chemicals, particularly nutrients such as nitrogen and phosphorus, before its safe disposal or reuse. A study was aimed to test the performance of three specific biological processes at bench scale in removing nitrogen and phosphorus from RO-reject wastewater. Best performing process in bench scale study was further studied at pilot scale. Laboratory Scale Processes On merits of performances and previous experience, three processes were selected for testing for the reduction of concentrations of nitrogen and phosphorus in RO-reject water (KISR, 2007b). System A: A biological process of Up-flow Sludge Blanket Filtration (USBF) is known to perform nitrification, denitrification and phosphorous removal (Fig.1). Expected operating features of the process are the following: 1. System operates under extended aeration mode, 2. Carbon source externally added to carbon deficient wastewater, 3. Nitrification takes place

3 in aerated part of the reactor, 4. Denitrification takes place in the anoxic zone of the reactor, and 5. Phosphorus removal takes place in the extended aeration zone, and also while the reactor effluent filters through sludge under the sludge blanket in the clarifier. System B: A Cascaded biological aerator system with partial anaerobic condition appeared to be suitable for successful nitrification and denitrification with removal of nitrogen and phosphorus in usual domestic wastewater (Fig.2) (Nowak, 1999; Sudiana, 1999). It is a process with multiple aerators in series. The aerators are maintained at anoxic or oxygenated states to promote nitrification and denitrification in the process. The system was selected to be tested for specific RO-reject water with provision of adding carbon while operating the reactors at various fractions of aerobic and anaerobic sections. System C: A denitrifying process with bacterial growth on fixed anaerobic-porous media followed by an algae pond is expected to have the capabilities of denitrification due to anaerobic biological process (Intrasungkha and Garland, 1998) and of phosphate removal due to the presence of aquatic plants such as algae (Fig.3) (Vaillant, 2004). In the test units, nitrate is expected to be converted to nitrogen gas within anaerobic-porous media while algae in algae-pond assimilate phosphate into its body-mass. Algae have been selected for their fast growth and high phosphate intake per mass and its growth is easily controllable. Degradable carbon source is added with the inflow (RO-reject water) that is deficient in Biological Oxidation Demand (BOD) content. Wastewater Storage Reactor Add Carbon Source Anoxic Part Aerated part Effluent Clarifier Sludge Blanket Sludge Return Fig. 1. Up-flow sludge blanket filtration process (System A).

4 Feed Tank Dosing Pump Anaerobic Tank Aerobic Tank 1 Treated Stream Aerobic Tank Without Mixing Aerobic Tank 3 Aerobic Tank 2 Clarifier Sludge Fig. 2. Cascaded Aerator System with Partial Anaerobic Condition (System B) Feed Tank Feed Pump Influent Stabilizer Tank Fixed Media Sponge or Sand/Gravel Clarifie Effluent Pump & Water level control Florescence Light Algae Tank Algae Filter Wastage Fig. 3. Fixed media anaerobic process for denitrification and algae process Methodology - Laboratory Scale Study Feed. The units were operated with synthetic wastewater resembling the RO-reject water produced in laboratory. Table 1 shows the quality of typical RO-reject water from the plant (Personal Comm., 2007). The use of synthetic waste in the study was mainly to apply better

5 control on feed chemical concentrations of N, P and various carbon sources in the systems. Synthetic RO reject water was prepared in the laboratory as feed, keeping the chemical parameters within range of values appearing in Table 1, which shows the measured quality of actual RO-reject water. Table 1. Quality of RO Rejects Water - Advanced Treatment Plant, Kuwait Parameter Value (Feb,2007) ph 7.29 Conductivity (µs/cm) 9201 TSS (mg/l) 7 COD (mg/l) 183 TDS (mg/l) 4,600 N-NO 3 (mg/l) 29 T PO 4 (mg/l) 63.1 Alkalinity (as CaCO 3 ) (mg/l) 371 Cl- (mg/l) 1,580 SO 4 (mg/l) 2,272 Table 2 shows the chemical ingredients used to provide normal quality of wastewater (Intrasungkha et. al. 1999). To spike N and P chemicals in the feed, NaNO 3 and KH 2 PO 4 were used. Three chemicals (methanol, acetate and glucose) were tried separately for supplying carbon needed for bacterial activity. Carbon to nitrogen ratio in the feed was maintained at 4-6:1. Table 3 shows a scheme for adding the carbon source (Sudiana, 1999; Intrasungkha et. al. 1999). In order to add required salinity to feed water that resembles ROreject water, NaCl was added at a rate of 0.2 g/100 ml. The resulting feed water had about 8.7 ph and 6,000 µs/cm conductance. Table 2. Trace-Chemical Ingredients in Synthetic Waste Source: Intrasungkha, et al., 1999 Ingredients Concentration/ liter of Synthetic WW (g/l) Ingredient Concentration/ liter of Synthetic WW (g/l) (NH 4 ) 2 SO FeSO H 2 O K 2 HPO NaCl 0.3 NaHCO MnSO H 2 O MgSO 4.7H 2 O 0.1 KH 2 PO CaCl Na 2 MoO KCl 0.02

6 Table 3. Guidelines for Adding Source Compounds for Different Levels of NO 3 and PO 4 Concentrations in the Synthetic Wastewater Source Quantity of Source Compound for Desired Compound Level of Nitrate (N-NO 3 ) NaNO g/l for 36 mg/l N-NO 3 Conc./l of WW Quantity of Source Compound for desired level of Phosphate PO 4) KH 2 PO g/l for 60 mg/l PO 4 Conc./l of WW (~19.6 mg/l P) Main features - Laboratory Systems Three bench-scale systems were designed for a flow range of 50 to 150 l/d. Design features of three laboratory units are shown in tables 4, 5 and 6. The systems were operated simultaneously for 105 days with varying chemical concentrations and feed flow. Table 4. Physical Properties of Bench Scale System A: Up-Flow Sludge Blanket Filtration Item Quantity/Dimension Number of reactor tanks 1 Depth (m) 0.3 Total volume of the reactor (m 3 ) (0.25x0.5x0.3) Anoxic volume/total Volume 0.34 Number of clarifier 1 Surface area of clarifier (m 2 ) Volume of clarifier (m 3 ) (Conical) Depth of clarifier (m) 0.3 Table 5. Physical Properties of Bench Scale System B: Cascaded Reactor System Item Quantity/Dimension Number of reactor tanks 5 Number of anoxic reactor tanks Variable Depth (m) 0.2 Volume of each reactor tank (m 3 ) (0.27x0.14x0.2) Anoxic Vol./total vol. of reactor system Variable Number of clarifier 1 Surface area of clarifier (m 2 ) Volume of clarifier (m 3 ) (Conical) Depth (m) 0.3

7 Table 6. Physical Properties of Bench-Scale Systems C: Anaerobic Denitrification on Selected Media Bed and Algae Treatment for Phosphate Removal Item Quantity/Dimension Number of denitrification tank 1 Depth of denitrification tank (m) Total volume of denitrification tank (m 3 ) (0.76x0.11x0.305) Mode of operation Attached growth of denitrifying bacteria Type of media Sponge/gravel-sand mix Porosity of sponge media 48% Porosity of gravel-sand media 45% Number of algae tank 1 Volume of algae tank (m 3 ) (Conical) Depth (m) Light supply (24 hrs/day) Tungsten lamps Number of clarifier in algae system 1(Attached at bottom of algae tank) Surface area of algae clarifier (m 2 ) 0.03(0.179x0.179) Volume of algae clarifier (m 3 ) (Conical) Depth of algae clarifier (m) 0.08 Inflow to bench scale systems were synthetically prepared to resemble RO reject wastewater (Table 1) except three parameters N-NO 3, total PO 4 and BOD 5. BOD 5 was the result of adding external carbon source methanol, acetate or glucose. These three parameters varied from one test case to other. Table 7 shows the range of the variations of these parameters. Table 7. Range of parameters N-NO3, total PO4 and BOD5 in bench scale process influent System N-NO 3, mg/l Total PO 4, mg/l BOD 5, mg/l A B C Laboratory Tests Laboratory tests for water-quality parameters were conducted in the laboratory at the advanced Wastewater-Research Plant, Kuwait. Main parameters measured were temperature, ph, total-suspended solids, volatile-suspended solids, settleable solids, chemical-oxygen demand (COD), BOD, conductivity, total-dissolved solids, sulfate, sulfide, total nitrogen (TN), Phosphate (PO 4 ), chloride, NH 4 -N, alkalinity as CaCO 3, NO 3 -N, total coliform and salmonella. Methodology for laboratory analysis followed standard methods (APHA, 2005).

8 Results Laboratory Scale Study Results on the performance of three systems were recorded for 79 test cases (System A: 13 with glucose, nine with methanol and five with acetate; System B: 10 with glucose, 10 with methanol and six with acetate; and System C: eight with glucose, 10 with methanol and six with acetate). Average performance of selected parameters of systems A, B and C appears in tables 8, 9 and 10 respectively. Test cases are designated by letters for reference. First and second letters in the case-designation indicate the system and carbon source, respectively. For example the case AG indicates system A operated with glucose as carbon source and AM indicates system A operated with methanol. Table 8. Average Effluent Quality with Respect to TN-N, PO 4 -P, BOD 5 and COD in Process A Parameter Average of All AG Cases Average of All AM Cases Average of All AA Cases COD BOD TN-N PO 4 -P Table 9. Average Effluent Quality with Respect to TN-N, PO 4 -P, BOD 5 and COD in Process B Parameter Average of All BG Cases Average of All BM Cases Average of All BA Cases COD BOD TN-N PO 4 -P Table 10. Average Effluent Quality with Respect to TN-N, PO 4 -P, BOD 5 and COD in Process C Parameter Average of All CG Cases (mg/l) Average of All CM Cases (mg/l) Average of All CA Cases (mg/l) COD BOD TN-N PO 4 -P in Denitrification Unit Effluent PO 4 -P in Algae Pond Effluent

9 Evaluation of Data Laboratory Scale Study Tables 8, 9 and 10 show average pollutant concentrations of four parameters: TN, PO 4, BOD 5 and COD for three processes. Special interest of the study was to observe the removal efficiency of TN and PO 4. Table 11 contains the average performance in percentage in reducing these chemicals from the feed water. Overall BOD 5 and COD removal was very good and was as per with expected outcome of conventional biological systems (Metcalf and Eddy, 1986). Table 11. Average Performance of Three Laboratory-Scale processes in Removing TN and TP in Synthetic RO-Reject Wastewater. Test Cases Removal of TN as N (%) Removal of TP as P (%) Carbon Source G M A G M A Average Process A Average Process B Average Process C G = Glucose, M= Methanol, A= Acetate This performance was consistent irrespective of the carbon source. Average range of BOD 5 removal in processes A and B was between 79 to 88%, while COD removal in these processes was between 79 and 83%. Average TN removal in process A was between 46 and 53%, while it was between 55-60% in process B and 81-85% in process C. Average TP removal in process A was between 43 and 52%, while it was between 47 and 51% in process B and 87-92% in process C. In consideration of target TN and PO 4 removal, the process B had slightly better performance than that of A. However process C performed much better than processes A and B. The application of the algae process following the denitrification reactor reduced TP to as low as mg/l (Table 10). A comparison of media used for fixed-growth denitrification appears in figure 4. Two media of sponge with a porosity of 48% and crushed gravel with a porosity of 45% were tested. It appeared that gravel media had slightly better performance. Figure 4 also depicts comparative performance of using carbon sources of glucose, methanol and acetate in process C. It appeared that better performance was achieved from glucose and acetate with the latter having slightly higher performances than those observed with glucose. Considering anticipated path-way of synthesizing and metabolizing carbon into bacterial cell, acetate is expected to be readily taken into cell with minimum amount of activity and energy (McKinney et al., 1978). The preference of acetate use by bacteria is evident from the results.

10 Percent Removal Test Groups 1=CG Sponge 2=CG Gravel 3=CM Sponge 4=CM Gravel 5= CA Sponge 6=CA Gravel TN-N Removal PO 4 -P Removal Fig. 4. Average TN-N and PO4-P Removal in Process C with Sponge and Gravel media for carbon sources glucose, methanol and acetate Processes A and B were specifically operated at extended aeration mode to facilitate nitrification and denitrification simultaneously. Process A had an average hydraulic detention time of 19 h, while average hydraulic detention time in process B was 24 h. The best performing bench-scale process, however, appeared to be system C containing the denitrification process carried by bacterial growth on fixed media with subsequent removal of phosphate in an algae pond. Table 12 shows the operational and design specifics of process C. Table 12. Operation and Design Specification of Process C - Denitrification by Attached Growth Bacteria and Phosphate Removal by Algae Growth Operation Specification Hydraulic Detention Denitrification media Hydraulic velocity thru the media Depth of media Denitrification rate per media surface area normal to flow direction Denitrification rate per microbial mass Average Value 10 h m/h 0.76 m 2 (mg/l/h)/m mg TN/mg VSS/h Hydraulic Detention in algae tank (24 h/d 31 h exposure to light) Surface Loading 1 m 3 /m 2 /det. time Depth of algae pond 0.31 m Phosphate (P) removal rate per algae mass 0.07 mg PO 4 -P/mg VSS /h

11 Pilot Scale Study In the laboratory scale study, the best performing system was found to be one that consisted of two unit processes of denitrification and algae reactor arranged in series (Process C). The operating specifications of pilot system C appear in Table 13. The schematic diagram of the pilot system is shown in Fig. 5. Pilot Process Feed. The system feed water was RO reject wastewater from Sulaibiya wastewater treatment plant (The Ministry of Pubic Works, Kuwait). The inflow was supplied to the pilot system at a rate of 42 l/h. The external carbon source was glucose in 55 test cases. Glucose was added in the inflow at an average rate of g/m 3 RO reject wastewater. Feed Carbon Sources. Several initial tests were performed at the first two weeks of the study using acetate (30 g/m 3 ) for seven days and glucose (30 g/m 3 ) for seven days. The TN and TP removal were between 70 to 80% without showing any preference for any one of carbon sources. The results were similar to those observed in the bench-scale study. Hence, for convenience of uses, glucose was selected for the remainder of the pilot system operation. The preferred dose of glucose addition was 10 mg/l. The observation extracted from the tests with varied glucose addition indicated that, as long as the glucose dose is around 10 mg/l, the performance of the system in TN and TP removal would remain consistently high (Fig. 6). Table 13. Main Features of Pilot System Item Value Inflow 1 m 3 /d Effective Denitrification tank volume 1 m 3 Effective Denitrification tank depth 0.75 m Effective Algae tank volume 1.3 m 3 Effective Algae tank depth 0.5 m Average Hydraulic Detention Denitrification media 10 h Average Hydraulic Detention Algae tank (24 h light) 31 h Depth of algae pond 0.31 m Surface loading - algae pond 1 m3/m2/det. (h)

12 Inflow Distribution Tank Clarifier Flow Divider Algae Tanks Denitrification Tank Inflow Pumps RO Reject Wastewater Storage Tank Compositor Bi-hourly Samples Effluent Discarded Thickened Algae Analysis and Evaluation of Pilot System Results Inflow (RO Reject Wastewater) Quality Fig. 5. Schematic diagram of the pilot system. The quality of RO reject wastewater (feed) remained more or less steady and consistent (Table 14). Quality parameters varied in narrow range. The standard deviation of qualityparameter values (Table 14) clearly indicated the narrowness of the value ranges in the majority of parameters, except parameters COD, and alkalinity. Percent Removal Glucose Addition (g/m 3 of RO Reject Wastewater) TN TP Fig. 6. Pilot system TN and TP removal vs. glucose addition in RO reject wastewater. Considering conductivity, the water may be classified as brackish in quality. High COD and very low BOD 5 values was the result of the application of extended-aeration biological processes, ultrafiltration and RO in the MPW wastewater plant. It is apparent that for further treatment by any biological process, BOD needed to be raised by adding external carbon source.

13 Table 14. Average, Max. Min. and Standard Deviation of Influent (RO Reject Wastewater) Quality Parameters in Pilot Process Parameters Units Average Max Min St. Deviation Temperature o C ph Conductivity µs/cm 6, ,110 5, COD mg/l N-NO 3 mg/l TN mg/l Total PO 4 mg/l Alkalinity mg/l BOD 5 mg/l Pilot Plant Effluent Quality and Nitrogen and Phosphorus Removal The system consisted of two unit processes of biological denitrification in anoxic condition and an algae reactor. The main aim of the denitrification unit was to reduce/remove N specifically nitrate. The algae reactor unit was also aimed at to reduce/remove phosphorus. Table 15 shows the summary (average, maximum, minimum and standard deviation) of 55 sets of data of the final effluent quality of the pilot system. In the denitrification unit, bacteria utilized carbon, nutrients (N and P).Therefore, the changes expected in pollutant parameters in this unit were mainly N and to a lesser extent, P. However, the high COD value in RO reject water with insignificant amount of BOD 5, indicated that any carbon in inflow COD was not degradable by normal mixed culture bacterial mass (Table 14). The existence of some non-degradable carbon in pilot effluent COD is apparent from the results (Table 15). In the algae tank, mainly P intake into algae mass took place. The principal nutrients required are N and P. Other trace elements, such as iron, Cu and molybdenum etc. are also used. It was expected that the RO reject wastewater contained these trace elements in adequate quantity. The main element that was reduced in the process of algae culture was P (Metcalf and Eddy, 1986). Due to activity related to CO 2, the ph in the final effluent was expected to be little high. The ph in the final effluent of pilot system was found to be slightly high around 8.4 (Table 15). In the absence of light, respiration of algae produces oxygen. Respiration also occurs in the presence of light, but at much lower extent. As the pilot system was provided with light for 24 h a day, oxygen production from algae respiration was expected to have minimal effect on the overall ph condition. In the pilot system, TN and TP were reduced on the average by 76 and 86 % respectively (Table 16). The maximum and minimum reduction of TN was 82 and 60 %, respectively.

14 The maximum and minimum reduction of TP was 92 and 72 %, respectively. This removal brought down the influent average TN from 76 mg/l to 13.9 mg/l in the final effluent (Tables 14 and 15). TP went down from influent average of 29 mg/l to effluent 3.3 mg/l. Microbial quality of total bacterial count, total coliform and fecal coliform were measured in final effluent stream every week for three months. Average total bacterial count, total coliform and fecal coliform were 14.75x10 5 CFU/100ml, 6.6x102 MPN/100ml and 5.8x10 MPN/100ml, respectively. It is apparent that a re-chlorination will bring down such concentrations to levels that are acceptable for restricted irrigation. A preliminary total-cost estimate of the process C (pilot system) appeared to be 0.03 KD/m 3 (1KD 3.5 USD) without the use of external carbon source. In such case, instead of external carbon source, primary treated wastewater is recommended to be mixed with RO reject water for supplying organic carbon raising the BOD 5 in process inflow to mg/l. However adding glucose for raising BOD5 in process inflow might raise the unit cost to 0.19 KD/m 3. Table 15. Average, Maximum, Minimum and Standard Deviation of Effluent Quality Parameters in Pilot Process Parameters Units Average Max Min St. Deviation Temperature o C ph Conductivity µs/cm COD mg/l N-NO 3 mg/l TN mg/l Total (PO 4 ) mg/l Alkalinity mg/l BOD 5 mg/l Table 16. Summary of Pollutant Removal Efficiency in Pilot Processes Average Removal in Percentage of Parameters Units Inflow Quality Average Max Min St. Deviation Conductivity µs/cm COD mg/l N-NO 3 mg/l TN mg/l Total (PO 4 ) mg/l Alkalinity mg/l

15 Conclusions Based on the results of the bench scale and pilot scale study results, the derived conclusions are as follows: 1. A process comprising of biological denitrification process followed by algae growing reactor appeared to be a successful treatment option for treating RO reject wastewater produced in advanced wastewater treatment plants treating municipal wastewater. 2. The process performance results indicated that average TN and TP concentrations of 76 mg/l and 29 mg/l in RO reject wastewater can be removed on the average by 76% and 86%, respectively. 3. The final effluent concentrations of TN and TP in the final effluent remain at 13.9 mg/l and 3.3 mg/l, respectively. 4. The process effluent might be utilized for restricted irrigation for salt- tolerant grass and plant irrigation. 5. Expected cost of a fully fledged plant is KD 0.03 /m 3 if necessary degradable BOD equivalent is added from raw wastewater, while the cost is about KD 0.19/m 3 if the external source of carbon is supplied with glucose. Acknowledgements The authors would like to extend thanks to the Kuwait Foundation for the Advancement of Sciences (KFAS) and Kuwait Institute for Scientific Research (KISR) for financing the study. References APHA, AWWA and WEF, Standard Methods for Examination of Water and Wastewater. American Public Health Association, American Water Works Association and Water Environment Federation, USA Intrasungkha, N and Garland, C.D Characterisation of wastewater from seafood processing plants in Tasmania, Australia. Biores. Techno. (Report). Intrasungkha, N., J. Keller, and L.Blackall, Biological nutrient removal efficiency in treatment of saline wastewater. J.Wat. Sci. Technology, 39(6): KEPA EPA Regulations, No. 210 (Kuwait Environmental Public Authority), (In Arabic). KISR 2007a. Present and future wastewater quantities and reuse demand in Kuwait. Final Report Submitted to KFAS Kuwait. KISR 2007b. Nitrogen and phosphorous reduction/removal from RO reject wastewater bench and pilot scale study (proposal). McKinney, R.E., H.C.Tomlinson, and R.L.Wilcox Microbiology for Sanitary Engineers. New York: McGraw-Hill Book Company. Metcalf and Eddy Wastewater Engineering. New York, McGraw-Hill Book Company

16 Nowak, O., V. Kuhn, and V. Muller, A comparison of different concepts of the running-in of nitrification and denitrification in activated sludge plants. J. wat. Sci. Technology, 39 (6): Personal Comm. (Personal Communication), The Ministry of Public Works, Kuwait. Sudiana, I.M Metabolism of enhanced biological phosphorus removal and nonenhanced biological phosphorus removal sludge with acetate and glucose as carbon source. J. Wat. Sci. Technology. 39 (6): Vaillant, N Urban wastewater treatment by a nutrient film technique system with a valuable commercial plant species (Chrysanthemum cineraria folium Trey.), Environ. Sci. and Technology, 38 (9): 2101.