Eliminating smell of urine

Eliminating smell of urine

An Environment friendly method

Introduction

Urine decomposes naturally producing a strong, repulsive, pungent smell.The smell is mainly due to ammonia. Ammonia is also harmful if inhaled continuously for a long time. It reduces RBC counts in blood (Causes anemia) and paves way for other diseases.The smell is a nuisance in public urinals, schools, colleges, offices etc.The methods available to counter this problem includes application of chemicals such as bleaching powder, boric acid, phenol and masking the smell with less unpleasant smell.None of theses are fully satisfactory as they lead to other environmental problems. For example, they interfere In sewage treatment.

Analysing the problem

According to Wikipedia an adult produces 1 – 2 litres of urine per day.the urine is sterile when fresh. The average composition of human urine is as follows:

Urea: 9.3g / lChlorine:1.87g / lSodium: 1.17g / lPotassium: 0.75g / lCreatinin: 0.67 g / lpH: Close to 7.0 but can normally vary

between 4.4 and 8

The problem..Ammonia is produced by decomposition of urea as follows:

Attempts to precipitate and remove urea as urea nitrate or urea oxalate adducts failed because these precipitation reactions work only in concentrated solutions.

SolutionsThe urease enzyme comes from ubiquitous bacteria like Helicobacter pylori and most other microorganims and rootlets of plantsThis suggests that we can eliminate the smell by using (i) antibacterials (bacteriostats or bactericides) (ii) reactions of urea (iii) urease inhibitors or (iv) simply convert the ammonium carbonate to some other odourless compound.The fourth option appears to be the cheapest and best. For example, urine treated with gypsum, a cheap chemical converts ammonium carbonate into ammonium sulphate, an odourless compound.

Alternatives to calcium sulphate

Chemical Cost Reaction Remarks

Ca(NO3)2 (NH4)2CO3 + Ca(NO3)2 CaCO3 + 2NH4NO3

More soluble than gypsum

CaCl2 (NH4)2CO3 + Ca Cl2 CaCO3 + 2 NH4Cl2


MgSO4 (NH4)2CO3 + Mg SO4 MgCO3 + (NH4)2SO4


Mg(NO3)2 (NH4)2CO3 + Mg(NO3)2 MgCO3 + (NH4)2SO4


MgCl2 (NH4)2CO3 + MgCl2 MgCO3 + 2NH4Cl


Implementation

Calcium sulphate has a low solubility in water. One liter of urine requires 26.66g of calcium sulphate which requires 14 litres of water to dissolve. Therefore, it is best added as a suspension of the finely divided powder. It may be kept in the cistern. After every use a quantity of the suspension is used to flush the urine. The urine and the flushings are collected in a tank. There will not be any smell in the place or in the collected material. Ecosan type toilets can be made to separate the solids from urine.

Gypsum

Gypsum is a common mineral found in association with sedimentary rocks. Gypsum is deposited in lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. It is often associated with the minerals halite and sulfur. Gypsum is also formed as a by-product of sulfide oxidation, amongst others by pyrite oxidation. It costs about Rs. 650 per tonne.

Disposal

The collected liquid along with the precipitate can be used for fertigation for crops such as sugar beet and in coconut gardens. The calcium carbonate counters the effect of sodium on soil and also prevents acidification of soil. However, excessive use of nitrogen containing fertilizers should not be encouraged as it may lead to nitrate pollution. It is best to remove most of the water by reverse osmosis and use the water in any suitable way. The concentrated fertilizer can be stored (preferably after sterilization) and used where it is needed.

QuantityCalculations show that India can produce 15.3 lakh t of fertilizers N in a year by converting 50% of all human urine. This is about 5% of the country’s requirement (289 lakh t) and equals34369313 GJ for manufacture alone (not counting transport). Animal urine can collected be treated in the same way.

Acknowlegements

Zero Waste Society of India

Indian Institute of Science

Campus, Bengaluru – 560 012

Tel: 23600977 22932613 22933107

Fax: 2360083

E-mail: [email protected]

www.zerowastesocietyofindia.com

Thanks for your patience

Technology

Eliminating smell of urine