Water Journal October 1994

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AUSTRALIAN WATER & WASTEWATER ASSOCIATIONVolume 21, No 5 October 1994 Editor EA (Bob) SwintonCONTENTSEditorial Correspondence 4 Pleasant View Crescent Glen…
AUSTRALIAN WATER & WASTEWATER ASSOCIATIONVolume 21, No 5 October 1994 Editor EA (Bob) SwintonCONTENTSEditorial Correspondence 4 Pleasant View Crescent Glen Waverley Vic 3150 Tel/Fax (03) 560 4752ASSOCIATION NEWS From the Federal President From the Executive Director Association Meetings2 3 7FEATURES Contracting Overseas •Australia Inc? Asia: A Shangri-la for Australian Contractors15Peter Gebbie, PWT •South East Asia: Experiences and Prospects17Peter Gilchrist, Chairman ~quatec-Maxcon •Expansion into New Areas18John Polich, Manager Warman Project Engineering Group •Exporting a New Technology19Tony MacCormick, General Manager Marketing Memtec •Joint Venture in Manufacturing21Peter Becker, Marketing Services Manager Vinidex Tubemakers •Trade Diplomacy, or Otherwise?22John Towns, Chief Executive ANI-Kruger •Some Recent ContractsNutrient Removal in Intermittent Cycle Plants2324RI Siebert Nitrogen and Phosphorus in Laboratory Scale Models3342Australian Water & Wastewater Inc ARBN 054 253 066 PO Box 388 Artarmon NSW 2064REPORTSFederal President 36David Dixon IAWQ Budapest Water Quality in America38 40Mike Chapman Drought and Disaster Planning41David WatsonDEPARTMENTS Industry News International Affiliates Products Books MeetingsACT - Alan Wade Tel (06) 207 2350 Fax (06) 207 6084 New south Wales - Mitchell Laginestra Tel (02) 412 9974 Fax (02) 412 9876 Northern Territory - Ian Smith Tel (089) 82 7244 Fax (089) 41 0703 Queensland - Leon De W Henry Tel (07) 233 1611 Fax (07) 233 1649 South Australia - Phil Thomas Tel (08) 259 0244 Fax (08) 259 0228 Tasmania - Jim Stephens i;el (002) 31 0656 Fax (002) 34 7334 Victoria - Mike Muntisov Tel (03) 600 1100 Fax (03) 600 1300 Western Australia - Alan Maus Tel (09) 420 2465 Fax (09) 420 3178WATER (ISSN 0310- 0367)P Haines, J Nielsen, B Druery, J BallIAWQ Flotation ConferenceBranch Correspondentsis published six times per year February, April, June, August, October, December byJ Brodsky, FE Grey The Salmon-Q Water Quality Model:A Murray Darling ApplicationF R Bishop, Chairman B N Anderson, G Cawston, M R Chapman P Draayers, W J Dulfer, GA Holder M Muntisov, P Nadebaum, JD parker A J Priestly, J Rissman30D H Abeysinghe, C A Borthwick The Economics of Wilderness AreasMargaret Bates Tel (02) 413 1288 Fax (02) 413 1047 A\Y/WA Federal Office Level 2, 44 Hampden Road Artarmon NSW 2064Editorial Board 14Damian Ryan, AUSTEMEX •Advertising Sales & Administration41246 47 48OUR COVER Solomon Islands, one of the countries that have received aid from the AustralianInternational Development A ssistance Bureau (A /DAB). Photograph - Norman Plant AIDAB/OIBRichard MarksExecutive Director Chris Davis Australi an Water & Wastewater Association assumes no responsibility for opinions or statements of facts expressed by contributors or advertisers and editorials do not necessarily represent the official policy of the organisation. Display and classified advertisements are included as an informational services to readers and are reviewed by the Editor before publication to ensure their relevance to the water environment and to the objectives of the Association. All material in Water is copy right and should not be reproduced wholly or1in part without the written permission of the Editor.Subscriptions Water is sent to all members of the AWWA as one of the privileges of membership. Non members can obtain Waier on subscription at an annual subscription rate of$35 (surface mail).TECHNOLOGYNUTRIENT REMOVAL IN INTERMITTENT CYCLE PLANTS RI Siebert*PART 1 COMPUTER SIMULATION Summary The presence of Poly-P organisms in the Woolgoolga Sewage Treatment Plant indicated that biological phosphorus removal may be achieved in intermittently decanted extended aeration (IDEA) sewage treatment plants. Through the use of a dynamic computer simulation of IDEA sewage treatment plants a number of operating regimes and configurations were trialled to determine which would give the greatest propensity for the biological removal of phosphorus. It was found that two configurations achieved significant biological phosphorus removal. They are an intermittent feed configuration and a configuration utilising an anaerobic reactor. This paper deals with the computer simulations. A later paper will summarise the results of pilot plant trials.Introduction At present the Woolgoolga Sewage Treatment Plant (in north eastern New South Wales) is dosed with alum to achieve phosphorus removal to a level not greater than 1 mg/L as required by the Enviromental Protection Authority. As part of the licence conditions the effluent is monitored for phosphorus on a weekly basis. It was found that during winter when the influent to the plant was colder the effluent phosphorus levels decreased from close to 1 mg/L to below 0.2 mg/I. Staining and microscopic examination of the sludge from the plant showed that there was growth of Poly P organisms and as such it was assumed some biological removal of phosphorus was occurring. Sludges from plants at Coffs Harbour and Sawtell were examined in the same manner and Poly P organisms were also found in these sludges. As with Woolgoolga it was assumed that some biological phosphorus removal was occurring. Ho et al (1993) reported on the performance of laboratory scale intermittently operated biological nutrient removal activated sludge processes and found that biological phosphorus removal was achievable. It was stated that phosphorus removal occurred in systems fed either continuously or intermittently provided that the basic 24requirements such as a COD:TKN ratio greater than 10: 1 and an influent concentration of RACOD greater than 50 i'ng/1 were met. Ho et al (1993) also stated that over-aeration adversely affects both nitrogen and phosphorus removal as simultaneous nitrification and denitrification was required during the aeration cycle to achieve biological phosphorus removal. Bliss et al (199 3) investigated and reported on the biological removal of phosphorus in the intermittently decanted extended aeration activated sludge process using data from plants at Bathurst, Urunga and Port Macquarie . The investigations centered on the use of anaerobic reactors up stream of the intermittent decant extended aeration (IDEA) process to provide an environment suitable for the biological removal of phosphorus. The report indicated that biological phosphorus removal could be achieved with the use of an anaerobic reactor and mixed liquor suspended solids (MLSS) recycle. Anecdotal data from a number of operators also indicated that with aeration equipment failure and subsequently long periods of little or no aeration IDEA plants exhibited a phosphorus release. When aeration was re-commissioned the plants achieved low levels of effluent phosphorus. This could indicate a level of phosphorus release and uptake as seen in biological phosphorus removal plants. Two studies were proposed on biological phosphorus removal in intermittent cycle plants at Coffs Harbour to determine operating regimes which would maximize the biological removal of phosphorus. They were the simulation of intermittent cycle plants, using a dynamic computer model , to evaluate theoretically various operating regimes, and the operation of a pilot plant constructed by Aeration and Allied Technology Pty Ltd. This paper deals with the dynamic computer simulation.Dynamic Simulation The computer model was developed using a model similar to that proposed by the IAWPRC (1986) and Wentzel et al (1989). The model operates on 17 substrates listed in Table 1. The fate of each of these substrates as used in the development of the dynamicmodel is presented in Figure 1 in a matrix format as described by IAWPRC (1986), and the equations are discussed below. It should be noted that the model does not consider the nondegradabl e so luble COD. It also only considers the nondegradable particulate COD as part of the inert sludge. These two items were not considered further as they do not take part in reactions on the model. Notwi thstanding, the model can be modified to include these two substrates. The model does not consider the nondegradable fractions of nitrogen and phosphorus as these also play no part in the biological reactions. These substrates could be added to the model if required.Reactions Hydrolysis of SBCOD to form ISCOD. In the model the SBCOD undergoes hydrolysi s by heterotrophs to form Table 1~ Substrates and acronyms considered Slowly biodegradable chemical oxygen demand Readily biodegradable chemical oxygen demand Internally stored RBCOD Poly B hydroxybutyrate Organic Nitrogen Ammonia Nitrogen Oxidised Nitrogen Organic Phosphorus Soluble Phosphorus Poly phosphate Alkalinity Imaginary Salt Dissolved oxygen Heterotroph concentrations Nitrifier concentrations Poly - P concentrations Inert sludgeSBCOD RBCOD IS COD PHB Org-N NH 4 NOX Org-P PHO PPH ALK SALTDO XBH XBN XBP XITable 2. Influent parameters. SubstrateInfluent mg/L200 200SBCOD RBCOD Org-N1342TH 4Org-P PHO210 270 100ALK XIpH7.41500 kLADWF*Coffs Harbour City Council WATER OCTOBER 1994!ism. The energy from the catabolism provides the energy for heterotroph growth or anabolism.· The steps of the conversion of RBCOD to Acetyl CoA, the energy transfer for anabolism and the anabolism were not used in the model as the conversion as described by Wentzel et al (1989) is less than the rate of removal of ISCOD and RDCOD to form heterotrophs as described by IAWPRC (1986 ), Metcalf and Eddy ( 1991 ), and others. The model would therefore have had an inordinately slow heterotroph growth rate. Also there was no published information on the rates of anabolism from energy produced. The rate used for the combined reaction is consistent with the rate of heterotroph growth published by Metcalf and Eddy (1991 ) and others. In the model the ISCOD is utilized in preference to the RBCOD. The figure used in the model for yield in the growth of heterotrophs Yh is given by WRC (1984), Wentzel et al (1989 ), IAWPRC (1986) and others. The figure used is 0.67 g heterotrophs as COD per g COD removed. Using the composition of cells as given by Metcalf and Eddy (1991 ):RBCOD which is stored in the heterotrophic biomass as RBCOD (ISCOD). The ISCOD is then available 'for the reactions of aerobi c heterotroph growth and anoxic heterotroph growth using oxygen and nitrate as electron acceptors repectively. The ISCOD produced in this reaction is transferred immediately into the cell. It is therefore not available for uptake as PHB by Poly-P organisms. This hydrolysis also releases into solution the nitrogen and phosphorus bound in organic matter producing ammonia nitrogen and soluble phosphorus. This reaction also includes the conversion of the released nitrogen to ammonia and the utilization of the hydrogen ion. In the model the hydrolysis is assumed to occur in aerobic, anoxic and anaerobic conditions. This is consistent with the findings of Wentzel et al (1989). The rate of hydrolysis is as given by IAWPRC (1986) as 3.0 g SBCOD per day per g het erotrophs (as COD) and is temperature dependent. Aerobic growth of heterotrophs.The model for the growth of heterotrophs is simplified in that it addresses the growth of heterotrophs using ISCOD and RBCOD as a singular reaction. In reality ISCOD and RBCOD must reduce to Acetyl CoA or a similar substrate prior to it being utilized as the substrate for catabo-C6o Hs10 23 N12The rate lior heterotrop h growth is given by IAWPRC (1986) as 5.0 g cells per day per g cells at pH 7.2 and is affected by pH and temperature, and the concentrations of RBCOD, oxygen and so lubl e phosphorus. Anoxic growth of heterotrophs.The anoxic growth of heterotrophs occurs using nitrate as an electron acceptor. In the model this reaction occurs at a rate equal to 80% of the aerobic reaction reaction rate (after IAWPRC 1986). This equates closely to the rates described by Barnard in Barnes and Gttenfield (1986) and Griffith (1993) as Kdn. l plus Kdn.2 which occur when both RBCOD and SBCOD are available. The three rates usually quoted were not used in this model as the model includes the hydrolysis reactions and the lysis of biomass. The slower rates of 0.101 (Kdn.2) and 0.072 (Kdn.3) are on ly applicable to the combined reactions of hydrolysis of SBBOD then utilization of ISCOD/RBCOD, and lysis of cell matter then hydrolysis to ISCOD/RBCOD then utilization of the ISCOD/RBCOD respectively. Based on an electron balance l g of nitrate is equivalent to 2.857 lg of oxygen. In the model the nitrate removed is equated to an equivalent ISCOD/RBCOD removed as follows:Pit can be determined that, for cell growth: Per g ISCOD or RB COD removed: 0.0155Yh g of soluble phosphorus, 0.084Yh g of ammonia nitrogen and 0.3Yh g of alkalinity are utilised and the oxygen demand is I - Yh g.(I - Yh) NOX removed= ,- - - 2.8571x RB COD removedFigure 1 Matrix S BCOO RBCOD ISCODHydrolysis of BOD toRDB.,PH130'1-NNH.NOXOrg-PXBHXDNXDPXIALKReaction rates DO •.... G- - -BODIXBH~J..Tl<N /800 ,.. 1bcMt+l.571 4+I.,.,Anoldc growth of heterotrophie biomass- 0.°'4• Y,OPH/BOOKabov-e+I-0.01551v,.,- (1 - YJ-,...-0..) IV,Y,-0.0155 1v,( I . YJ...l.5714 1v,~t · l~ooj •~Jt '- X ROB ~Y.it.,1 - 0.0..11v.KdaB-0.01 55 11 Y,0.4'44IAerobic growth of Poty-P biomass•(7. 1411 - -(4.57 U O.JV.) Y.)Y,~~ ~ •TKNk.,,•00J~+ O.N7J1' 0.0IJ4O.l1:l.4J+ O.N 12+ 0.0114Ux1.4J+ 0.067J+ 0.0U4I., .,Deacy of Poty-P biomass.,Release of Poty-P.?;-:5~ "-0~~""'UJ -0WATER OCTOBER 199481 LUJ-o( I • V.)b.., x fn (temp),.,b,. x ln(temp),.,b.x ln(temp)~:0-0-0-0::>::>C..011....C:k,.o·OOjx ln (pH)x ln (temp)x XBPb.x ln (temp)::, ..8 >. co ~ u C =~ 8-0 'rJ ~ !lC: ...Si .Q~ 0 >-. ~g -x ln{lemp)J X8Hb. x ln(temp)., .?;-~NOX1w,tch • NOXjk.-,-PHB/XBP,.,..I>.-0.J 1 V,Y,Decay of nitrifying· biomass:So ]o 1o ... o ~o ';;;Q :;U :.u ;U - u "'3~ - ... :§~NOX •~"h1'~-PHBIXBP - - , ~-DO -jo.015SV,O.lxJ .4JI, fa(pH) ,fa~,mp), XBH.. tn(pH) .. tn{lemp) xXBHII--:;:11 .,ROB., 00,~"h OOswitch • 00-0.4144...- 0.0M• Y,-IRelease of PHBNOX j k.,.•NOXk.,,•00~,IfnlPH) ifn{temp)x XBH11,. • ROB ( I - VJAerobic growth of nitritying biomass Sequestering of ROB to PHB1 ln(temp) .. xBHIt,• 800/XBHHydrolysis of organic P to soluble phosphorusDecay of heterotrophic biomassPPH"Hydrolysis of TKN toNH 4Aerobic growth of heterotrophlc biomassPHOo ·c:2-~C E "'0C£~..8"' "t' ~.i::: ~2 t~ -~-g :0::>"' -a e .QoEl g .f~ Z< zz at 00"'~0C"'0-0-o o.i:::Cl) 0.o~ -.;;~E 0 l5(.):aP. 0ti"' 0~.; ,.:: ·5"'~E 0 l5 ~i5 t ::C:l5 z ~"' :2 0 "' t:"' .E0:s ]<C"'00 I<'0v,, c Helerolroph gro/'1h rale ""' • Nilrffier grOW1h rate 11, • Poly-P growth rate k, • Rate or hydrolysis k,, • 1/2 ra te for hydrolysis Ii;. • Substrate 112 rate for he1erotroph k.,." • DO 112 rate for aerobic heterotroph k, • rate of sequeslering ~- rate of lysis or cells Y • yield25Similar to the aerobic growth of heterotrophs 0.015 5Yh g of phosphorus is removed per g ISCOD/RBCOD removed. The grams of alkalinity produced in the reaction (in terms of CaCO 3) can also be calculated from the grams of ISCOD/RBCOD removed as: 3.5714 x (I - Yh) - - - -- x RB COD removed 2.857 1The rate for anoxic growth of heterotrophic biomass is affected by pH and temperature, and the concentrations of ISCOD/RBCOD, oxygen, nitrate and soluble phosphorus. Aerobic growth of nitrifiers. As with the oxidation of ISCOD/RBCOD the model is simplified in that the reactions to convert soluble nitrogen to ammonia are not considered. It is assumed that entrapped available organic nitrogen is converted directly to ammonia nitrogen during hydrolysis. Figures for yield in nitrifier growth Yn are again given by WRC (1984), Wentzel et al (1989), IAWPRC (1986) and others. In general the figure used is 0.15 g nitrifiers as COD per g ammonia nitrogen nitrifi ed. The oxygen and other substrate demand for cell growth can then be determined as: Per gram ammonia nitrogen nitrified: 4.57 13 - Yn g oxygen 0.0155Yn g of soluble phosphorus 7.1428 - 0.3 Yn g of alkalinity. I - 0.084Yn g of nitrate are produced.The rate for nitrifier growth using ammonia as the substrate is taken as 0.35 g cells per g cells.day at pH 7.2 and is affected by pH and temperature, and the concentrations of oxygen, ammonia-nitrogen and soluble phosphorus . Sequestration of PHB. Only the readily degradable RBCOD in solution is available for sequestering to form PHB . The sequestering of RBCOD to form PHB is a first order reaction. After Wentzel et al (1989) it is proposed that Poly-P cells will sequester 1 g of RBCOD for the release of 0.4844 g of stored phosphorus. This phosphorus is released to form part of the available soluble phosphorus substrate. The figure of 0.4844 is derived from the production of ADP from ATP per mole of RBCOD converted to Acetate and taken up to form PHB. Growth of Poly-P organisms. A figure for yield of Poly-P biomass Yp is given by Wentzel et al (1989) as 0.639 g Poly-P per g PHB removed. The substrate demands for cell growth can then be determined as: Per g PHB removed: I - Yp g oxygen 0.0155Yp g of soluble phosphorus, 0.084Yp g of ammonia nitrogen, 0.3Yp g of alkalinity.0.9 to 1.1 g phosphorus are taken up and stored as Poly-P (Wentzel et al,1989) (a figure of 1 is used in the model). 26The rate for Poly-P biomass growth is given as 1.0 g cells per day per g cells and is affected by pH and temperature, and the concentrations of oxygen, PHB and soluble phosphorus. Decay of biomass. The model assumes endogenous decay or lysis of the biomass which both removes active biomas s from the reactors and produces SBCOD, Org-N and Org-P. For the model it is also assumed that 0.2 of the biomass remains as undegradabl e nonactive or endogenous mass after lysis. The lysis of 1 g of biomass produces: 0.8 g of SBCOD as COD 0.0 124 g of organic phosphorus 0.0672 g of organic nitrogen and 0.2 g of inert mass as COD ¡In the decay of Poly-P biomass the stored PHB is released to form RBCOD and the stored Poly-P is released to form soluble phosphorus. The rates of endogenous decay or lysis of the biomass are given for the different types of biomass as: 0.24 per day for heterotrophs 0.04 per day for nitrifiers 0.04 per day for Poly-P biomassThe rate of lysis is temperature dependent. pH Control. The pH of the reactions was modelled by assuming the presence of a buffer salt as described below. In the presence of a buffer Salt pOH = pKb + logl0( - - .- ) AlkaliThis can be rewritten as pH = 14 + Logl0(Kbx C CO 3 ) a Salt x 50000As Kb, 14, and 50000 are constants the equation may be used in the form Salt pH = -Log l0( - - - ) CaCO 3Variations in alkalinity in the form of CaCO 3 due to chemical and biological reactions will give rise to variations in pH. Dissolved oxygen. The dissolved oxygen (DO) is modelled in terms of power consumed. A transfer of 1.5 Kg oxygen per Kw .hr at a DO of 0 mg/Lis assumed. The modelling of DO is therefore: 1.5 x Power DO = DO 0 + - - - -- x (DO,at - DO 0) Volume x DOsat where DO 0 is the DO at time 0 and DO," is the DO at saturationSludge settling. In the settling cycle the settlement of sludge is modelled using the equation V = Vo e-kXas described by White and Vesiland in White (1975). In the model the sludge settles to a concentration defined by the stirred settled volume index (SSVI) of the sludge. Again this is a simplification as compression of the sludge or Type IV settling are not considered.Although SSW. can be modelled, using the parameters of F:M ratio, DO:biomass ratio and the active fraction of the biomass, the model used in the preparation of this paper assumed an SSVI of 150 ml/gFormat of model The model is a time step integrating model. That is, at the start of a time period the model adds the influent volume and mass of substrates to each reactor or
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