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ACWa builds leachate treatment plant
USTRIALNEWS ACWabuilds leachate treatment plant ACWa Systems Ltd h a s won £520,000 c o n t r a c t to design and build a new leachate t r e a t m e n t p l a n t for site remediation. The contract was a w a r d e d for t h e c o m p a n y ' s innovative a n d cost-effective design of a five-stage system u t i l i s i n g a c o m b i n a t i o n of technologies including ultrafiltration, two reverse-osmosis processes, and traditional chemical t r e a t m e n t . The site, formerly used for t h e p r o d u c t i o n of v a r i o u s chemical products, h a s over a p e r i o d of y e a r s b e c o m e heavily c o n t a m i n a t e d . Rainfall causes leaching of cont a m i n a n t s , w h i c h are t h e n carried into local water courses. The brief required a t r e a t m e n t p l a n t to m e e t t h e r e q u i r e m e n t s a n d discharge c o n s e n t s s e t d o w n by t h e N a t i o n a l Rivers A u t h o r i t y , while m a i n t a i n i n g m i n i m u m r u n n i n g costs. Although t h e flow from t h e site is b a l a n c e d in a large lagoon, t h e volume to b e t r e a t e d still required m a j o r capital e x p e n d i t u r e o n large t r e a t m e n t vessels, a n d excessive r u n n i n g costs. The first stage of t h e ACWa system features a n ultrafiltration p l a n t (10 m 3 / h r o u t p u t ) to remove p a r t i c u l a t e a n d colloidal m a t t e r which m i g h t foul t h e l a t e r processes. The second and third stages (reverse-osmosis p l a n t s ) are used to c o n c e n t r a t e all t h e p r o b l e m c o n t a m i n a n t s into only 15% of t h e i r o r i g i n a l volume -- a six-fold concent r a t i o n factor. The p e r m e a t e from t h e RO stage (8.5 mS/ h r ) h a s a TDS level of a r o u n d 5 m g / l from a 6000 mg/1 feed.
C o n c e n t r a t e from t h e RO stages (1.5 m a / h r ) c o n t a i n s all t h e original c o n t a m i n a tion, c o n c e n t r a t e d six times. The reduced volume enables t h e following t r e a t m e n t processes t o be economicallysized a n d efficiently operated. In t h e c o n c e n t r a t e treatment, pH a d j u s t m e n t is used in c o n j u n c t i o n w i t h ferrics u l p h a t e d o s i n g to r e d u c e certain c o n t a m i n a n t s to a n acceptable form. pH adjustm e n t using NaOH is t h e n used to precipitate m e t a l oxides. S u p e r n a t a n t liquor from t h e s e t t l e m e n t t a n k is maint a i n e d a t 10°C o r a b o v e , before being p u m p e d forward to two ammonia-stripper towers, o p e r a t i n g in series, to bring a m m o n i a levels down below 30 mg/1. The concentrate stream (1.5 m a / h r ) is t h e n m i x e d with the permeate stream from t h e second RO p l a n t s (8.5 m a / h r ) to produce 10 m a / h r for discharge ( a m m o n i a diluted to 5 m g / l ) . Equipm e n t in t h e m i x i n g t a n k constantly m o n i t o r s conductivity, a m m o n i a , pH a n d flow, a n d if t h e w a t e r quality falls outside pre-set limits, diverts one or b o t h s t r e a m s b a c k to the lagoon for r e t r e a t m e n t . The u s e of a p p r o p r i a t e m e m b r a n e technologies comb i n e d w i t h more conventional t r e a t m e n t m e t h o d s is recognised by various bodies as 'Best Available Technique Not Entailing Excessive Cost'. ACTga ~ s I.g,d,ACWa House, Keighley Road, Skipton, North Yorkshire BD23 2UE, UI~ Tel: +44 (0)756 794794, fax: +44 (0) 756 790898.
Efficient filtration prevents reinfestation Asellus a n d o t h e r c r e a t u r e infestations t h a t have periodically b e e n a p p e a r i n g in w a t e r m a i n s at locations in t h e Severn-Trent BinleyWoods a r e a of Coventry, a r e n o w being effectively i n t e r c e p t e d from e n t e r i n g t h e system, by d u p l e x filters. T h e s e h a v e been supplied b y UK-based Plenty Filters Ltd, with one installed in t h e 6 inch a n d a n o t h e r in t h e 8 inch m a i n s a t t h e p o i n t of entry to t h e area. Asellus aquaticus and Asellus meridianus cannot swim, b u t move by a crawling 590
action, clinging tenaciously to t h e r u s t surfaces which form their feeding environment. Males die after copulation in April, a n d females after the young emerge in May. During these periods significant n u m b e r s have b e e n a p p e a r ing in t h e w a t e r supply -they are readily discernible a t u p to 16 m m long. A l t h o u g h dosing with Perm e t h r i n can be temporarily effective against t h e infestation, prior to t h e filter install a t i o n fresh c r e a t u r e s were subsequently entering the
Demineraliser train for Singapore JGC Corporation, Yokohama, J a p a n h a s selected t h e t e a m of Nippon Rensui C o m p a n y of Tokyo a n d Gaco Systems, a Meggitt Energy company b a s e d in Ontario, C a n a d a to design and manufacture a complete d e m i n e r a l i s e r syst e m for Singapore Refining Company's refinery u p g r a d e offshore a t Singapore. Singapore Refining Comp a n y is p a r t of a c o n s o r t i u m which includes British Petroleum a n d Caltex. JGC Corp h a s t h e c o n t r a c t to build a new residual catalytic cracker a n d MTBE p l a n t a t SRC's 220,000 b p d refinery located o n a n island off Singapore. The boiler feedwater treatm e n t system will supply 175
ma/hr demineralised water f o r s t e a m g e n e r a t i o n required for these additions to the refinery. The ion e x c h a n g e system includes a n activated c a r b o n filter, cation exchanger, a n d stratified bed a n i o n exchanger. The system will be delivered in early 1994. This project m a r k s a miles t o n e in t h e c o l l a b o r a t i o n between Nippon Rensui Company a n d Gaco Systems, b o t h respected water treatment c o m p a n i e s serving J a p a n e s e contractors on international projects. Gaco Systems, 54 Morton Avenue East, PO Box 1810, Brantford, Ontario N3T 5W4, Canada. TeL" + 1 519 759 0270, fax: + 1 519 759 0505.
Bag filter for nitrous oxides A bag filter is removing more t h a n 70% of t h e n i t r o g e n oxides, as well as all o t h e r p o l l u t a n t s , f r o m flue g a s e m i t t e d from a m u n i c i p a l waste i n c i n e r a t o r located in t h e J a p a n e s e city of Tsushima. The developer, Mitsubishi Heavy Industries Ltd, reports t h a t t h e p r o c e s s works by i m p r e g n a t i n g t h e glass-fibre fabric of t h e filter w i t h a b a n a d i u m p e n t o x i d e catalyst. In t h e system, a 25% solution of a m m o n i a , slaked lime a n d a fine clay p o w d e r ( t h e role of which is to form a protective film t h a t prevents t h e bag fabric clogging) are injected into t h e flue gas after it has passed through a
q u e n c h i n g chamber. S u l p h u r dioxide a n d hydrogen chloride react with the lime to form a solid cake that is removed periodically from t h e i n n e r walls of t h e bag filter. NOx reacts w i t h t h e a m m o n i a w i t h i n t h e bag, yielding nitrogen a n d water. NOx levels d r o p from 100150 ppm to less than 30 ppm, while removal efficiencies for HC1, SOx a n d flyash are more t h a n 98, 88 a n d 99%, respectively. Dioxins a n d mercury are also 'filtered' our by reaction with t h e filter c a k e a n d t h e flyash. T h e system can be readily retrofitted t o e x i s t i n g bag-filter
system -- t h e filters form a b a r r i e r a g a i n s t this. Severn-Trent Water serves a b o u t 5000 properties in t h e area, with water arriving t h r o u g h 6 a n d 8 inch mains. The flow ~rofiles are maxim u m 17 m o/ h r , average 8 m 3 / h r (6 inch), a n d m a x i m u m 85 m3/hr, average 45 m 3 / h r (8 inch). C r e a t u r e control is now effected by combining dosing a n d filtration. The d u p l e x filters provide a c o n t i n u o u s service w i t h o u t t h e need to stop t h e w a t e r flow. The c r e a t u r e s are c a u g h t in a b a s k e t , which facilitates filtration from 2 m m d i a m e t e r perforations down to 50 gm, d e p e n d i n g o n t h e specific requirement, with o t h e r op-
t i o n s if required. Duplex filters are available to suit p i p e sizes from 1 to 36 inches in cast construction, a n d larger w i t h welded construction. The Binley Woods operation is m a n u a l using interconnected screwed shafts a n d a n external handwheel, and eliminates any complete shutting-off of t h e w a t e r flow. A valve position i n d i c a t o r shows which c h a m b e r of t h e filter is onstream. The valve seats a n d m e s h inserts are replaceable; t h e valves a n d seats are of cast iron, a n d t h e shales a n d e l e m e n t s of stainless-steel.
systems.
Plenty Ltd, Hainbridge Road, Newbury, Berks. RG14 5TR, UI~ Tel: + 44 (0) 635 4263,fax: + 44 (0) 635 49758.
November 1993
Filtration & Separation
C o n c e n t r a t e from t h e RO stages (1.5 m a / h r ) c o n t a i n s all t h e original c o n t a m i n a tion, c o n c e n t r a t e d six times. The reduced volume enables t h e following t r e a t m e n t processes t o be economicallysized a n d efficiently operated. In t h e c o n c e n t r a t e treatment, pH a d j u s t m e n t is used in c o n j u n c t i o n w i t h ferrics u l p h a t e d o s i n g to r e d u c e certain c o n t a m i n a n t s to a n acceptable form. pH adjustm e n t using NaOH is t h e n used to precipitate m e t a l oxides. S u p e r n a t a n t liquor from t h e s e t t l e m e n t t a n k is maint a i n e d a t 10°C o r a b o v e , before being p u m p e d forward to two ammonia-stripper towers, o p e r a t i n g in series, to bring a m m o n i a levels down below 30 mg/1. The concentrate stream (1.5 m a / h r ) is t h e n m i x e d with the permeate stream from t h e second RO p l a n t s (8.5 m a / h r ) to produce 10 m a / h r for discharge ( a m m o n i a diluted to 5 m g / l ) . Equipm e n t in t h e m i x i n g t a n k constantly m o n i t o r s conductivity, a m m o n i a , pH a n d flow, a n d if t h e w a t e r quality falls outside pre-set limits, diverts one or b o t h s t r e a m s b a c k to the lagoon for r e t r e a t m e n t . The u s e of a p p r o p r i a t e m e m b r a n e technologies comb i n e d w i t h more conventional t r e a t m e n t m e t h o d s is recognised by various bodies as 'Best Available Technique Not Entailing Excessive Cost'. ACTga ~ s I.g,d,ACWa House, Keighley Road, Skipton, North Yorkshire BD23 2UE, UI~ Tel: +44 (0)756 794794, fax: +44 (0) 756 790898.
Efficient filtration prevents reinfestation Asellus a n d o t h e r c r e a t u r e infestations t h a t have periodically b e e n a p p e a r i n g in w a t e r m a i n s at locations in t h e Severn-Trent BinleyWoods a r e a of Coventry, a r e n o w being effectively i n t e r c e p t e d from e n t e r i n g t h e system, by d u p l e x filters. T h e s e h a v e been supplied b y UK-based Plenty Filters Ltd, with one installed in t h e 6 inch a n d a n o t h e r in t h e 8 inch m a i n s a t t h e p o i n t of entry to t h e area. Asellus aquaticus and Asellus meridianus cannot swim, b u t move by a crawling 590
action, clinging tenaciously to t h e r u s t surfaces which form their feeding environment. Males die after copulation in April, a n d females after the young emerge in May. During these periods significant n u m b e r s have b e e n a p p e a r ing in t h e w a t e r supply -they are readily discernible a t u p to 16 m m long. A l t h o u g h dosing with Perm e t h r i n can be temporarily effective against t h e infestation, prior to t h e filter install a t i o n fresh c r e a t u r e s were subsequently entering the
Demineraliser train for Singapore JGC Corporation, Yokohama, J a p a n h a s selected t h e t e a m of Nippon Rensui C o m p a n y of Tokyo a n d Gaco Systems, a Meggitt Energy company b a s e d in Ontario, C a n a d a to design and manufacture a complete d e m i n e r a l i s e r syst e m for Singapore Refining Company's refinery u p g r a d e offshore a t Singapore. Singapore Refining Comp a n y is p a r t of a c o n s o r t i u m which includes British Petroleum a n d Caltex. JGC Corp h a s t h e c o n t r a c t to build a new residual catalytic cracker a n d MTBE p l a n t a t SRC's 220,000 b p d refinery located o n a n island off Singapore. The boiler feedwater treatm e n t system will supply 175
ma/hr demineralised water f o r s t e a m g e n e r a t i o n required for these additions to the refinery. The ion e x c h a n g e system includes a n activated c a r b o n filter, cation exchanger, a n d stratified bed a n i o n exchanger. The system will be delivered in early 1994. This project m a r k s a miles t o n e in t h e c o l l a b o r a t i o n between Nippon Rensui Company a n d Gaco Systems, b o t h respected water treatment c o m p a n i e s serving J a p a n e s e contractors on international projects. Gaco Systems, 54 Morton Avenue East, PO Box 1810, Brantford, Ontario N3T 5W4, Canada. TeL" + 1 519 759 0270, fax: + 1 519 759 0505.
Bag filter for nitrous oxides A bag filter is removing more t h a n 70% of t h e n i t r o g e n oxides, as well as all o t h e r p o l l u t a n t s , f r o m flue g a s e m i t t e d from a m u n i c i p a l waste i n c i n e r a t o r located in t h e J a p a n e s e city of Tsushima. The developer, Mitsubishi Heavy Industries Ltd, reports t h a t t h e p r o c e s s works by i m p r e g n a t i n g t h e glass-fibre fabric of t h e filter w i t h a b a n a d i u m p e n t o x i d e catalyst. In t h e system, a 25% solution of a m m o n i a , slaked lime a n d a fine clay p o w d e r ( t h e role of which is to form a protective film t h a t prevents t h e bag fabric clogging) are injected into t h e flue gas after it has passed through a
q u e n c h i n g chamber. S u l p h u r dioxide a n d hydrogen chloride react with the lime to form a solid cake that is removed periodically from t h e i n n e r walls of t h e bag filter. NOx reacts w i t h t h e a m m o n i a w i t h i n t h e bag, yielding nitrogen a n d water. NOx levels d r o p from 100150 ppm to less than 30 ppm, while removal efficiencies for HC1, SOx a n d flyash are more t h a n 98, 88 a n d 99%, respectively. Dioxins a n d mercury are also 'filtered' our by reaction with t h e filter c a k e a n d t h e flyash. T h e system can be readily retrofitted t o e x i s t i n g bag-filter
system -- t h e filters form a b a r r i e r a g a i n s t this. Severn-Trent Water serves a b o u t 5000 properties in t h e area, with water arriving t h r o u g h 6 a n d 8 inch mains. The flow ~rofiles are maxim u m 17 m o/ h r , average 8 m 3 / h r (6 inch), a n d m a x i m u m 85 m3/hr, average 45 m 3 / h r (8 inch). C r e a t u r e control is now effected by combining dosing a n d filtration. The d u p l e x filters provide a c o n t i n u o u s service w i t h o u t t h e need to stop t h e w a t e r flow. The c r e a t u r e s are c a u g h t in a b a s k e t , which facilitates filtration from 2 m m d i a m e t e r perforations down to 50 gm, d e p e n d i n g o n t h e specific requirement, with o t h e r op-
t i o n s if required. Duplex filters are available to suit p i p e sizes from 1 to 36 inches in cast construction, a n d larger w i t h welded construction. The Binley Woods operation is m a n u a l using interconnected screwed shafts a n d a n external handwheel, and eliminates any complete shutting-off of t h e w a t e r flow. A valve position i n d i c a t o r shows which c h a m b e r of t h e filter is onstream. The valve seats a n d m e s h inserts are replaceable; t h e valves a n d seats are of cast iron, a n d t h e shales a n d e l e m e n t s of stainless-steel.
systems.
Plenty Ltd, Hainbridge Road, Newbury, Berks. RG14 5TR, UI~ Tel: + 44 (0) 635 4263,fax: + 44 (0) 635 49758.
November 1993
Filtration & Separation