Nowra Chemicals manufacture a variety of disinfectants, detergents, alum and other chemicals. The products are manufactured batchwise as required, in a range of mixing vessels and reactors. As each product batch is completed and decanted, the reactor or mixing vessel is washed out in preparation for the next batch. Alum is manufactured in dedicated tanks, but has been accidentally spilled into the wastewater system in the past. Currently, all wash water is directed to a holding tank, where it is pH adjusted with hydrochloric acid and pumped to a settling tank. The sludge collected in the tank is periodically pumped to filter bags, where it is allowed to drain, and eventually transferred to a landfill. The separated water is discharged to the sewer as trade waste.

The sludge is thought to be generated when anionic and cationic waste streams are mixed together. There is potential for improvement of the wastewater system by separating the water streams, thereby minimising the amount of sludge produced, handled and disposed.

The objective of the product mixing trials was to identify which product wash-waters or spillage would react together to form sludge. This data can be used to divide the products into groups in which each member of the group can be mixed with any other member, without creating sludge.

The product mixing trials comprised:

• identification of the products to be tested;
• selecting the test solution concentration;
• consecutively mixing the test solutions, observing and documenting reactions; and
• interpretation of the results.

In addition all alkaline salt test solutions were mixed with 0.5M hydrochloric acid, as these chemicals may form solids under neutral or acidic conditions.

Products Tested

Mr Ken Chapman of Nowra Chemicals identified 146 products which were consistently manufactured in 1994, along with the amounts produced Table 1 attached). This list did not include products which were manufactured in very small amounts (say a single batch) in the year. The list of 146 was divided into 13 categories as follows:

GROUP		Amount produced in 1994 (kgs)
A	Cations	137,650
B	Nonionic - acidic	83,491
C	Nonionic - alkaline	110,091
D	Nonionic - neutral	66,693
E	Anionic - alkaline salt	352,620
F	Anionic - caustic	192,464
G	Anionic - neutral	142,082
H	Emulsions	133,857
I	Oils	159,572
J	Dyes	14,810
K	Nonionic - alkaline salt	310,392
L	Anionic - acidic	8,400
M	Miscellaneous	2,350 (excluding alum)
		6,482,350 (including alum)
TOTAL		1,714,472 (excluding alum)
		8,194,472 (including alum)

In discussion with Mr Chapman, the list of 146 was reduced to 41 products by including those products which:

• could potentially enter the waste water system (via washouts or spills); and
• were thought to be the most reactive; and/or
• were representative of (similar to) a number of other products; and/or
• were produced in significant quantities.

All products in Group J (Dyes) were excluded from the testing program as the washwater for these products is drummed and re-used, and does not enter the wastewater system.

The final list of 41 products (Table 2) represents approximately 70% w/w of the products manufactured in 1994.

Concentration of Test Solutions

The concentration of products entering the waste water system was expected to vary. In discussion with Ken Chapman and Armin Stintman (subcontracted chemist), a nominal concentration of 2% v/v of product in water was selected as the test solution concentration.

Mixing Trials

The mixing trials were completed by Armin Stintman between 26 June and 6 July, 1995, and comprised:

1. 1. Making up 2% v/v test solutions of each of the 41 products;
2. 2. Systematically adding 50mls of each solution to 50mls of every other solution (eg A1 with A2, A1 with A3 etc), giving a total of 780 tests. The test solutions were placed in 100 ml wide-mouth screw top glass jars, and mixed by shaking;
   
3. 3. Observing the subsequent reaction (if any), and classifying it as follows:
   
   • NR         No reaction;
   • CC         No solid formed, but a colour change observed;
   • SP         "Slight Precipitate" formed (cloudy effect);
   • LP         "Light Precipitate" formed (trace solids);
   • MP         "Medium Precipitate" formed (some solids);
   • HP         "Heavy Precipitate" formed; or
   • Eoil Oily   emulsion formed.
   
   

   Those combinations which resulted in a reaction were retained.
   

4. Random inspection of the retained tests on 6 July (between 2 and 10 days after completion of the test) to asses possible changes in reactions over time.
   

Alkaline salts vs hydrochloric acid tests were conducted in stirred glass beakers. Hydrochloric acid (0.5M) was added to 100mls of each of the Group E and K test solutions, while monitoring the pH of the mixture and noting any reactions, until the mixture had reached pH3.

Product Mixing Trials

Raw results are presented in Table 3. Of a total 780 tests:

• 455 gave no reaction;
• 169 produced a slight precipitate;
• 94 gave a light precipitate;
• 27 produced a medium precipitate;
• 19 produced a heavy precipitate;
• 6 gave a colour change; and
• 10 produced an oily emulsion.

Notes: In all cases 100 mls of 2% solution was added to a stirred beaker under a pH meter. The initial pH was noted, then 0.5 HCl acid added inrementally, until a pH of 3.0 was reached. Any reaction or precipitate was noted, as well as the volume of acid required to reach pH 30.

The following observations were also noted:

• It was not possible to make up a test solution of product number I3 (Crodowax), as it was a virtually solid wax-like material.
• A number of Group H and I test solutions (Emulsions and Oils) were cloudy (or opaque), or had some "precipitate" present prior to testing. These test solutions have been marked with an asterisk on Table 3. Reactions involving these solutions were assessed based on any apparent increase in opacity or solids formed.

Results have been assessed on a group basis for the following reasons:

• Reactions were relatively consistent within each group (for example, no group D test solutions reacted with Group B test solutions); and
• Results for the 40 tested products are to be extrapolated to cover the total 146 products.

Group results are summarised below:

GROUP

A

B

C

D

E

F

G

H

I

K

L

A

Cationic

X

-

-

-

-

-

-

-

-

-

-

B

Nonionic

(acidic)

X

X1

-

-

-

-

-

-

-

-

-

C

Nonionic

(alkaline)

•

•

-

-

-

-

-

-

-

-

-

D

Nonionic

(neutral)

•

•

•

•

-

-

-

-

-

-

-

E

Anionic

(alkaline salt)

X

X

•

•

•

-

-

-

-

-

-

F

Anionic

(alkaline caustic)

X

•

•

•

•

-

-

-

-

-

-

G

Anionic

(neutral)

X

•

•

•

•

•

-

-

-

-

-

H

Emulsions

X

X

X

X

X

X

X

X

-

-

-

I

Oils

X

X

X

X

X

X

X

X

X

-

-

K

Nonionic

(alkaline salt)

X

•

•

•

•

•

•

X

X

•

-

L

Anionic

(acidic)

X

X

•

•

•

•

•

X

X

X

-

M

Miscellaneous

X

•

•

•

•

•

•

X

X

X

X

NB:	•	100% "No Reaction" when constituents of each group are added together
X		Reactions (colour change, formation of precipitate or oily emulsion) were observed for one or more tests
X1		A "slight precipitate" only was observed when B1 was added to B2.

The majority of test results inspected did not change significantly over time.

Alkaline Salts vs Hydrochloric Acid

The raw results for these tests are listed in Table 4. Results indicate that:

For the 7 of the 9 tests, no reaction was observed. The exceptions were E1 - Bleach (Cl₂ gas liberated) and K2 - Sodium aluminate (precipitate formed); and

Product E8 (Plate finisher) is actually anionic acidic (group L)

Notes: In all cases 100 mls of 2% solution was added to a stirred beaker under a pH meter. The initial pH was noted, then 0.5 HCl acid added inrementally, until a pH of 3.0 was reached. Any reaction or precipitate was noted, as well as the volume of acid required to reach pH 30.

The conclusions of the product mixing trials are as follows:

To minimise the amount of sludge generated in the waste water system, the washwaters and spillage could be segregated as follows:

TANK 1 - ANIONS	TANK 2 - NONIONS	SLUDGE TANK
Group E	Group B	Group A
Group L	Group C	Group H
Group F	Group D	Group I
Group G	Group K	Group M
Total mass* = 695,566	Total mass* = 570,667	Total mass* = 431,079 (excluding alum)

* Based on 1994 production figures

Precipitates may be formed when adding acid to neutralise Group K washwaters.

TABLE 2

PRODUCTS TESTED IN MIXING TRIALS

GROUP #	SYMBOL	PRODUCT NAME
A. Cationic	A1	Acidic concrete
	A2	Lemon diso
	A3	Diso phenyle
	A4	Fabric conditioner
	A5	Marfilm B
	A6	Reynolds RT9
B. Nonionic-acidic	B1	ABT Solution 5
	B2	Negadev DK
C. Nonionic-alkaline	C1	Euroclean
D. Nonionic-neutral	D1	Aragum
	D2	Radiator coolant
	D3	Lubricant 5100
	D4	Sanichem 2
E. Arionic-alkaline salt	E1	Bleach
	E2	Cir cleaner 4
	E3	Crown X
	E4	HJ Cleaner
	E5	HD alkali
	E6	Lubeclean sil
	E7	Posidev
	E8	Plate finisher
F. Anionic-alkaline caustic	F1	Lubeclean LF
G. Anionic-neutral (detergents)	G1	Detergent concentrate
	G2	AFFF6
	G3	Derminal
	G4	Fount 405
H. Emulsions	H1	Heavy duty plate cleaner
	H2	Washout storage gum
	H3	Eroral
I. Oils	I1	Antioxidant
	I2	Crodoglaze
	I3	Crodowax
	I4	Declear
	I5	Engine degreaser
	I6	GP washout
	I7	Mould oil SP
	I8	TMP oleate
K. Nonionic-alkaline salts	K1	Negader AQ3
	K2	Sodium aluminate
L. Anionic-acidic	L1	Reynolds RT 12
M. Miscellaneous	M1	Alum normal
TOTAL	41

Notes:
(1) Group J (dyes) not included in mixing trials as these do not enter effluent system
(2) Alkaline salts form gel-like solids when at pH outside (more acidic) than pH = 10.5. Hydrocloric acid is used to adjust effluent pH. These compounds should also be tested with HCl.

Notes: In all cases 100 mls of 2% solution was added to a stirred beaker under a pH meter. The initial pH was noted, then 0.5 HCl acid added inrementally, until a pH of 3.0 was reached. Any reaction or precipitate was noted, as well as the volume of acid required to reach pH 30.

TABLE OF CONTENTS