Man­ag­ing Wa­ter

In this month’s col­umn Sa­has­rana­man builds a case for com­pul­sory wa­ter au­dit along the lines of en­ergy au­dit. It would bring the nec­es­sary dis­ci­pline in the in­dus­try to sur­vive the in­creas­ingly wa­ter-stressed times. The 3R prin­ci­ple of Re­duce – Re­use – Re

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No other month re­minds us more about wa­ter in In­dia than May. The hard­est hit are our ther­mal power plants, many of which are lo­cated in highly wa­ter-stressed ar­eas. They are forced to oper­ate at part loads or even shut down. The lat­est data re­leased by Cen­tral Wa­ter Com­mis­sion is cause for alarm. The av­er­age live wa­ter stor­age of all of our wa­ter reser­voirs have shrunk to a low of 20%.

In­dus­try ac­counts for 19% of fresh wa­ter us­age glob­ally, while agri­cul­ture and house­holds use 69% and 12% re­spec­tively. But this does not tell the whole story. Agri­cul­ture is now us­ing 3 times more wa­ter than 50 years ago and this is ex­pected to in­crease by 19% by 2050. Since food has to be top pri­or­ity, in­dus­try will be un­der in­creas­ing wa­ter stress in the com­ing years. With 18% of global pop­u­la­tion and only 4% of the global wa­ter, In­dia’s sit­u­a­tion is ex­tremely pre­car­i­ous. In­dian agri­cul­ture con­sumes as much as 87% of wa­ter with in­dus­try ac­count­ing for 8%. In­dus­try gets the last pri­or­ity in our Na­tional Wa­ter Pol­icy and thus suf­fers most even though it ac­counts only for 8%. It is no se­cret that our agri­cul­ture is waste­ful in its wa­ter us­age. But un­less there is a strong po­lit­i­cal will, in­dus­try will con­tinue to bear the brunt of wa­ter scarcity.

Wa­ter in In­dus­try

Among in­dus­try, ther­mal power plants are the big­gest con­sumers with a whop­ping share of 88%. Other wa­ter guz­zling in­dus­tries are en­gi­neer­ing, pulp and pa­per, tex­tiles, steel and sugar. When bench­marked glob­ally on wa­ter us­age, In­dian in­dus­tries come across as very in­ef­fi­cient. There is thus scope for con­serv­ing wa­ter through process mod­i­fi­ca­tions and bet­ter op­er­at­ing prac­tices.

The big­gest us­age of wa­ter by in­dus­try is for cool­ing, most of which is lost to at­mos­phere by evap­o­ra­tion. Next comes rais­ing steam. Wa­ter is used in prod­uct pu­rifi­ca­tion, as a sol­vent or for wash­ing. Wa­ter is also used for pro­duc­ing vac­uum. In ad­di­tion, wa­ter also some­times form part of the prod­uct, ei­ther as a dilu­ent or by par­tic­i­pat­ing in the chem­i­cal re­ac­tion.

Man­ag­ing fresh wa­ter re­quires the ap­pli­ca­tion of the 3R (Re­duce – Re­use – Re­cy­cle) prin­ci­ple:

• Process changes to re­duce wa­ter de­mand

• Re­use of waste­water from one process in an­other process.

• Re­cy­cle of waste­water in same process.

Re­duce

Wa­ter us­age can be re­duced through process mod­i­fi­ca­tion and re-en­gi­neer­ing. Cool­ing loads can

be min­imised by ap­ply­ing pinch tech­nol­ogy to in­crease process to process heat ex­change. Heat pumps can re­duce cool­ing loads of dis­til­la­tion col­umns. Ma­jor cool­ing loads can be trans­ferred to air, keep­ing only a small resid­ual load for cool­ing wa­ter. Wa­ter make-up to closed cool­ing wa­ter cir­cuits can be re­duced by op­er­at­ing at higher con­cen­tra­tion cy­cles and adopt­ing bet­ter wa­ter treat­ment meth­ods.

Up­grad­ing wa­ter-ring vac­uum pumps to the ex­pen­sive dry vac­uum pumps re­duce wa­ter and waste­water.

Wash­ing and rins­ing op­er­a­tions con­sume lot of wa­ter that end up as waste­water. Ef­fi­ciency of wash­ing can be in­creased by pro­vid­ing tur­bu­lence, ei­ther through spray­ing or air ag­i­ta­tion. In­creased con­tact time in mul­ti­stage wash­ing also im­proves ef­fi­ciency. A coun­ter­cur­rent mul­ti­stage wash­ing sys­tem can re­duce wa­ter con­sump­tion by as much as 90% com­pared to a sin­gle-stage process.

Wa­ter is pu­ri­fied ei­ther through ion-ex­change or Re­verse Os­mo­sis, and there is loss of wa­ter in both process. By choos­ing bet­ter ionex­change resins and im­proved col­umn de­sign, wash­ing and rins­ing cy­cles can be re­duced to save wa­ter. Im­proved RO mem­branes in­crease re­cov­ery and re­duce wa­ter lost in re­jects.

The ma­jor im­ped­i­ment to im­ple­ment­ing most of these mea­sures is that they do not yield de­cent pay­back and that is be­cause wa­ter is not re­al­is­ti­cally priced.

Pinch Tech­nol­ogy

Much of the wa­ter used in in­dus­try ends up as ef­flu­ent. Re­use and re­cy­cle of waste­water not only re­duces fresh wa­ter us­age, but also re­duces the ef­flu­ent dis­pos- al prob­lems. Op­por­tu­ni­ties for wa­ter re­use and re­cy­cle are not easy to spot, es­pe­cially in large chem­i­cal plants. Pinch tech­nol­ogy, which has been ex­ten­sively used for heat in­te­gra­tion in large process plants, can also be used to dis­cover pos­si­bil­i­ties of wa­ter re­use and re­cy­cle. Us­ing pinch tech­niques fresh wa­ter re­quire­ment can be matched with treated re­cy­cle wa­ter. Lev­els of treat­ment can be matched with fresh wa­ter spec­i­fi­ca­tions to re­duce costs.

Treat­ing waste­water for re­use and re­cy­cle is not al­ways easy. Some con­tam­i­nants are in­tran­si­gent and dif­fi­cult to biode­grade. Tech­nol­ogy li­cen­sors mostly shy away from of­fer­ing guar­an­tees on ef­flu­ent qual­ity and quan­tity, es­pe­cially for new tech­nolo­gies that haven’t fully ma­tured. Also, op­er­a­tors treat waste­water guar­an­tees lack­adaisi­cally com­pared to en­ergy con­sump­tion for ex­am­ple. They are of­ten will­ing to let go off short­fall in waste­water guar­an­tees and man­age it by di­lut­ing with clean wa­ter as long as the li­cen­sor picks up the tab.

Wa­ter Au­dit

There is a strong case for wa­ter au­dit along the lines of en­ergy au­dit. Un­like en­ergy, de­mand-sup­ply equa­tion doesn’t seem to gov­ern wa­ter pricing. Most peo­ple refuse to even con­sider it as a com­mod­ity and treat it as a gift of na­ture. Wa­ter au­dit will change this per­cep­tion in a big way. The prin­ci­ple be­hind wa­ter au­dit­ing is – if you don’t mea­sure it, you can’t man­age it. Au­dit will re­quire com­pa­nies to mea­sure wa­ter used at ev­ery point and trace where it ends up. Wa­ter bal­ance will re­veal how and where wa­ter is lost.

Wa­ter au­dit will have to be made com­pul­sory for des­ig­nated in­dus­tries. This will re­quire an act of par­lia­ment to es­tab­lish a body sim­i­lar to the Bureau of En­ergy Ef­fi­ciency. In­dus­tries will have to em­ploy cer­ti­fied wa­ter man­agers. They will have to also get a wa­ter au­dit done an­nu­ally by a cer­ti­fied wa­ter au­di­tor and demon­strate con­tin­u­ous im­prove­ment. This will pro­mote bench­mark­ing of wa­ter con­sump­tion. Com­pul­sory wa­ter au­dit will bring the re­quired dis­ci­pline in in­dus­try.

The long-term vi­sion of in­dus­try should be to lobby with the au­thor­i­ties to get it an even foot­ing as agri­cul­ture in the Na­tional Pol­icy. Agri­cul­ture can eas­ily save wa­ter by adopt­ing prac­tices like drip ir­ri­ga­tion, which is how­ever cap­i­tal-in­ten­sive. As part of their CSR, big in­dus­tries can adopt farms in their taluka or dis­trict and im­ple­ment such wa­ter con­ser­va­tion meth­ods. Such col­lab­o­ra­tion be­tween in­dus­try and agri­cul­ture is the need of the hour.

It is un­re­al­is­tic to ex­pect dra­matic sav­ings by wa­ter man­age­ment. Im­prove­ments in in­dus­try would be in­cre­men­tal, but as the say­ing goes lit­tle drops of wa­ter make the mighty ocean.

K Sa­has­rana­man In­de­pen­dent Con­sul­tant - Process En­gi­neer­ing, En­ergy, Util­i­ties and Safety

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