Pamela

Nitrite

The values of nitrite in all sites except tap water is very low and remains fairly constant. Furthermore, nitrites occur very seldom in significant concentration.

The cause of the higher nitrite value in tap water is probably formed by drinking water distribution systems that use chloramines.

Even so, the level of nitrite is safe and has no much adverse effect to human and living organisms.

Nitrate

The nitrate levels for all the sites are relatively constant and lie within the acceptable range of below 50mg/L (following WHO's guidelines).

Nitrate concentration is low as the source, water that flows into the grease trap, contains a low concentration of nitrate as well. This is probably because the detergents or soaps used had a low concentration of nitrate in them.

There were prevalent nitrate content in the next 4 sites. However, having Tank b4 Pond as a control, we know that the concentrations are normal and probably a natural-occurring concentration in the environment.

Laboratory Testing

· COD
1) The sample is refluxed with known amounts of potassium dichromate and sulphuric acid.
2) The excess dichromate is measured by spectrophotometry, as the amount of organic matter is proportional to the potassium dichromate consumed.

· Phosphate
1) Ammonium molybdate is combined with the sample containing phosphate ion and form a yellow colour solution
2) A reducing agent, ascorbic acid is added to produce a blue colour solution that is proportional the amount of phosphate present.

· Hardness
1) EDTA, a tritrating agent is added into the sample.
2) Hardness is present if the dye turns reddish-pink from blue colour.

· Suspended Solids
1) Weigh the filter paper with the ceramic dish.
2) Filter paper is placed on the filtration unit and a sample vessel is attached to filter assembly.
3) The filter paper is left to dry in the over at ±105®C for an hour in the oven
4) Then it is being measured again for the amount of solids on the filter paper

· Chloride
1) An indicator, potassium chromate is added into the sample
2) Silver nitrate is used as a titrant in the process of titration.
3) The titred value is noted when the solution turns reddish-brown and calculated by the formula.

Chloride

As chloride occurs in all natural waters, there is a slight amount of it existing in the tap water, inlet and outlet, pond 1 and pond 2. However the chloride is significantly high in the grease tap. It could be that students wash off salt minerals from their hands using tap water, which then increases the value of chlorides containing in the grease tap.

Phosphate

There is a minimal amount of phosphate contained in tap water because polyphosphates are used in water supplies as a means of controlling corrosion.

A high level of phosphate in the grease tap is mainly contributed by detergents, soaps and even traces of human wastes (urine) when a person washes their hands at the sink.

Hydroponics in the Phytoremediation System and along the C-shaped pond absorb the high concentration of phosphate, that becomes a pollutant if not removed, as part of the treatment system.

Plants like the Papyrus Sedge absorb Phosphate ions

Conductivity

The conductivity in all the six sites is relatively high, between 100mho to 200mho, tap water being the lowest. This measurement suggests a high amount of ions dissolved in the water.

The presence of ions in the Grease Trap may have been caused by detergents and soaps which contained ions such as nitrates and phosphates. The decomposition of organic matter by bacteria to ions (e.g. food molecules) and chemicals that get washed down (e.g. pen ink) would have also contributed to the ionic content in the water.

As the water passes out of the Grease trap and into the phytoremediation system, Organic-Nitrogen is decomposed by bacteria into Ammonia-nitrogen and finally into Nitrate-Nitrogen which flows into the C1 Inlet causing the height in conductivity.

Taken up by the hydroponics, ion concentration decreases in C2 Outlet and Pond 1, resulting in the steady decrease of conductivity as well.

However, conductivity increases in Pond 2. We assume this is caused by the wastes generated by the organisms living in the or due to pollution by the air.

Colour

The colour data in the grease tap is significantly high. The main reason is because teachers use the tap water to wash their hands which may be dirtied with pen ink, food molecules, and other coloured particles.

A high amount of colour in the outlet could be due to organic matters, such as decaying leaves and suspended particles, such as soil.

Decaying leaves & Suspended Particles contribute to Colour Data

The inlet, pond 1 and pond 2 colour data is caused by suspended particles especially coloured clay soils.